A Crystalline Dioxaborirane through Borylene Activation of Dioxygen

A Crystalline Dioxaborirane through Borylene Activation of Dioxygen | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Crystalline Dioxaborirane through Borylene Activation of Dioxygen Guanrong Chen, Zhaoyang Liu, Jiancheng Li, Liu Leo Liu, Hanqiang Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9677735/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Dioxaboriranes, the boron analogues of dioxiranes, are three-membered BO 2 main-group peroxides whose synthesis and characterization remain highly challenging. Herein, we report the straightforward synthesis and characterization of a crystalline dioxaborirane via direct borylene activation of triplet dioxygen. Mechanistic studies indicate a stepwise process involving end-on oxygen coordination, intersystem crossing, and subsequent ring closure. Single-crystal X-ray diffraction reveals a notably elongated O–O bond, reflecting the combined effects of Pauli repulsion and ring strain. Furthermore, this dioxaborirane undergoes facile O–O bond cleavage in the presence of Lewis acids such as AlMe 3 and AgOTf, yielding well-defined boron-oxygen species. This work establishes a rare example of an isolable dioxaborirane, elucidates the mechanism of borylene O 2 activation, and opens new avenues for the controlled exploitation of strained main-group peroxide motifs in synthesis and reactivity studies. boron borylene dioxaborirane dioxygen Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Main Text Dioxygen (O 2 ) activation has continued to attract considerable attention because of its critical importance across multiple fields. Reactive oxygen species (ROS) play indispensable roles in environmental remediation, 1 where their oxidative capacity is harnessed to degrade persistent pollutants, and in biological systems, where they function as regulated signaling mediators that control immunity and cellular metabolism. 2 Despite the abundance, environmental benignity, and intrinsic oxidizing capacity of molecular oxygen, its triplet ground state imposes a substantial kinetic barrier that limits its direct reaction with most organic substrates under ambient conditions. 3 Overcoming this constraint to access ROS, including singlet dioxygen ( 1 O 2 ), superoxide (O 2 •− ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (•OH), has traditionally relied on transition-metal catalysts capable of promoting O 2 reduction and generating peroxide- or superoxide-derived intermediates. 4 Representative systems include metalloenzymes that transiently form reactive metal-oxygen species and metal-organic frameworks (MOFs) that facilitate reversible dioxygen binding and activation. 5 For organic compounds containing an O 2 motif, the archetypal examples are dioxiranes and peroxides; however, these two classes of molecules are fundamentally distinct in their electronic structures (Fig. 1 a). In acyclic organic peroxides, the O − O linkage is destabilized by repulsive interactions between the lone pairs of the two oxygen atoms. By contrast, cyclic dioxiranes impose a rigid three-membered-ring geometry that enforces close and nearly parallel alignment of oxygen lone pairs, thereby amplifying Pauli repulsion and ring strain. 6 Consequently, whereas many acyclic organic peroxides are isolable compounds, dioxiranes are generally encountered as highly reactive intermediates. 7 A similar distinction is apparent in boron−oxygen chemistry: although boron compounds have been extensively explored for dioxygen activation, 8 the resulting boron peroxide species are predominantly confined to acyclic architectures or embedded within five- or six-membered rings, rather than adopting highly strained dioxaborirane motifs. 9 Early studies by Bourissou showed that peroxide compound I could be generated from the reaction of phosphine−boronate complexes with singlet dioxygen. 10 Agapie demonstrated that related peroxide compound II could be accessed through cooperative dioxygen activation involving a Lewis acidic borane and transition-metal reductants. 11 Subsequent work by Erker led to isolable bis(borane) superoxide compounds III using radical/borane pairs. 12 Piers, Kinjo and Harman further established that dual boron centers embedded in aromatic frameworks are capable of activating O 2 to form boron peroxides IV − V . 13 This cooperative dual-boron-center strategy was reinforced by Driess and Frenking, who found that diboraoxiranes reacted with O 2 to afford diboraperoxides VI . 14 Collectively, these well-defined bis(borane) superoxide and related peroxide species predominantly rely on dual active centers VII − VIII . 15 In contrast, the development of side-on peroxo species, namely dioxaboriranes, based on a single boron atom has lagged significantly behind. This gap is particularly evident in the chemistry of three-membered main-group heterocycles, where research efforts have thus far focused mainly on heavier chalcogen analogues, including dithiaboriranes, diselenaboriranes, and ditelluraboriranes, which are typically prepared from borylene or boron anion precursors. 6a, 14, 16 During the preparation of this manuscript, only one dioxaborirane was recently described by Cummins and Gilliard through the reaction of diazoboranes with dioxygen, which proceeds through nitrogen-to-oxygen exchange at the boron center rather than through a borylene intermediate (Fig. 1 c). 9 Cremer reported the synthesis of a dioxirane from the reaction of a transient triplet carbene with O 2 , 7 while Driess demonstrated that carbene-supported silylenes similarly reacted with O 2 to afford dioxasiliranes. 17 Phosphadioxiranes have also been obtained from the reaction of hypervalent phosphoranides with dioxygen. 18 Inspired by these precedents, we hypothesized that direct borylene activation of O 2 could provide a promising route to the long-sought synthesis of highly reactive dioxaboriranes (Fig. 1 d). Herein, we report the synthesis and single-crystal X-ray characterization of a dioxaborirane species, as well as its O − O bond cleavage in the presence of Lewis acids. To stabilize the reactive BO 2 three-member ring, a sterically encumbered environment was introduced around boron, leading to the synthesis of cyclic (alkyl)(amino)carbene (CAAC)-stabilized iminoborylene 2 , which can be viewed as BN‑embedded heterocumulenes. 19 Borylene 2 reacted smoothly with dioxygen to afford dioxaborirane 3 at − 20°C (Scheme 1 ). This conversion was clearly indicated by a shift in the 11 B{ 1 H} NMR signal from 57.6 ppm to − 2.8 ppm. Subsequent concentration of the reaction mixture and cooling to − 20°C yielded yellow crystals of 3 , which decomposed readily at room temperature. The time-dependent 1 H NMR in C 6 D 6 showed that the half-life of 3 at room temperature is approximately 10 hours (Figure S17 and S18). Single-crystal structural analysis reveals that compound 3 contains a three-membered ring composed of one boron and two oxygen atoms (Fig. 2 ). The O1 − B1−O2, B1 − O1−O2, and B1 − O2−O1 bond angles are 64.0(8)°, 57.3(5)° and 58.6(3)°, respectively, which reflect the significant ring strain. The B1 − O1 and B1 − O2 bond lengths (1.473(6) Å and 1.453(6) Å, respectively) resemble those found in anionic (1.471(1) Å and 1.468(1) Å) and neutral dioxaborirane (1.443(1) Å and 1.458(1) Å). 9 Meanwhile, the O1 − O2 bond distance of 1.553(5) Å is notably longer than those (1.280(4) − 1.507(4) Å) reported bridging O 2 systems 11b, 12a, 13–15, 15c and similar to that in dioxaboriranes (1.530(1) Å and 1.549(2) Å) 9 and dioxasiliranes (1.547(3) Å) 17 . The elongation of O1 − O2 bond, compared to that in bridging B − O−O − E complexes, is likely attributed to the combined effects of strong Pauli repulsion between oxygen lone pairs and inherent ring strain of three-membered ring (Figure S21). The bonding and electronic structure of 3 were further elucidated through density functional theory (DFT) calculations, complemented by frontier molecular orbital (FMO) and natural bond orbital (NBO) examinations. The intrinsic bond orbital (IBO) results confirm well-defined σ-bonding orbitals corresponding to the B1 − O1, B1 − O2, and O1 − O2 interactions (Fig. 3 ). Each oxygen atom bears a predominantly nonbonding lone pair orbital (96.1% on O1 and 95.4% on O2) oriented out of the B1 − O1−O2 plane. This highly localized electron density generates substantial Pauli repulsion, which contributes to the observed elongation of the O − O bond. Similarly, the in-plane lone pairs are even more localized with 98.8% of the density confined to the oxygen atoms. Further support comes from the Wiberg bond index of 0.97 for the O1 − O2 bond. Additionally, NBO charge analysis reveals considerable charge separation with a boron charge of + 0.81 a.u. and oxygen charges of − 0.49 a.u. and − 0.48 a.u., respectively (Figure S24). Although several reports have documented dioxygen activation by boron-containing compounds, 10–15 the detailed reaction mechanism still remains inadequately explored, largely due to the spin-forbidden nature of triplet dioxygen in such processes. 9, 20 To elucidate the mechanism of dioxygen activation by borylene, we conducted density functional theory (DFT) calculations to calculate the free energy (ΔG) and electronic energy (ΔE) using the reaction of 2 with 3 O 2 as a model. As illustrated in Fig. 4 , this process begins with borylene 2 donating an electron to 3 O 2 . This step proceeds via transition state 3 TS1 , which surmounts an activation free energy of 12.6 kcal/mol to form a triplet η 1 -O 2 -type superoxide intermediate 3 INT1 . This dioxygen addition step ( 3 TS1 ) is identified as rate-determining step, and its relatively low activation barrier is consistent with the experimentally observed rapid reaction at low temperature. Subsequently, 3 INT2 was successfully located by performing a relaxed scan of the potential energy surface (PES), which is 2.7 kcal/mol more stable than 3 INT1 . Minimum energy crossing point (MECP) calculations indicate that this system can undergo intersystem crossing from 3 INT2 to a more stable singlet intermediate 1 INT3 with a minimal energy barrier (ΔE) of 0.7 kcal/mol. Finally, 1 INT3 overcomes a relatively low barrier (ΔG) of 8.5 kcal/mol to rearrange to dioxaborirane. To further characterize the electronic interaction between borylene 2 and dioxygen, the relationship between the C2 − B1−N1 bending angle and energy was evaluated, and the corresponding torsional profile is plotted in Figure S26. This scan reveals that bending C2 − B1−N1 angle to 154.4° in the resulting bent structure 2b, which closely resembles that (155.5°) in 3 TS1 , requires only a minor energetic cost of 2.3 kcal/mol. This bent geometry endows 2b with pronounced electrophilicity by aligning the formally vacant p orbital on boron with sp 2 -hybridization, thereby lowering its energy. Consequently, the relevant unoccupied orbital on boron drops from LUMO + 9 (2.06 eV) to LUMO + 7 (1.55 eV), as illustrated in Figure S27. Then, the frontier molecular orbitals of 3 TS1 were examined. The singly occupied p orbital of the borylene boron atom in 3 TS1 is reflected in the SOMO. Meanwhile, the overlap between the π 2pz * orbitals of 3 O 2 and the π orbital of the Dipp-arene ring appears in the SOMO − 1 (Figure S28). This indicates electron transfer from the boron atom of borylene to the π 2py * orbitals of 3 O 2 , in contrast to the formation of dioxaboriranes by Cummins and Gilliard, in which free boryl anion or borylene intermediates are excluded. To better understand bonding interaction between borylene 2 and dioxygen, a comprehensive analysis by the extended transition state-natural orbitals for chemical valence (ETS-NOCV) was carried out. Figure S29 shows that the differential densities associated with these interactions dominate the bonding between 3 O 2 and borylene unit in 3 TS1 . The charge flow direction from blue to red regions indicates electron density transfer from the doubly occupied p orbital of borylene boron into the π 2py * orbitals of 3 O 2 with an associated energy of − 23.53 kcal/mol. The paramount importance of the O − O bond strength across diverse chemical processes motivates our investigation into its dissociation (Scheme 2 ). Compound 3 demonstrated notable reactivity toward AlMe 3 at − 20°C, cleanly yielding an alumoxane complex 4 . The molecular structure of 4 features a B − O−Al − O−Al bridging motif (Fig. 5 a). In complex 4 , the Al1 − O1 and B1 − O1 bond lengths of 1.775(2) Å and 1.338(2) Å, respectively, fall within the range reported for related compounds. 21 The Al1 − O2 and Al2 − O2 bond lengths of 1.843(2) Å and 1.868(2) Å are notably longer than the Al1 − O1 bond length of 1.775(2) Å. The controlled oxygen atom transfer by AlMe 3 provides a model for the interaction of reactive peroxide species with main-group Lewis acids. Upon treatment with 2 equiv. of AgOTf at − 20°C, compound 3 was smoothly converted to complex 5 . X-ray diffraction analysis of 5 clearly revealed a B = O double bond (Fig. 5 b). In the solid state, two independent Ag⁺ ions are present. Ag1 is bridged by two triflate anions and further coordinated by the B = O group and a Dipp-arene ring, whereas Ag2 is also bridged by two triflate anions and additionally interacts with B = O and C = N moieties. For complex 5 , the B1 − O2 bond lengths of 1.294(8) Å are in the range of those in previously reported oxoborane compounds. 22 The reaction of 3 with AgOTf cleanly affords an oxoborane−silver complex 5 , highlighting silver(I) as an effective reagent for accessing Lewis-acid-stabilized oxoborane fragments. Conclusions In summary, this work has established direct borylene activation of triplet dioxygen for accessing a dioxaborirane and reveals Lewis-acid-induced O–O bond cleavage, thereby expanding the reactivity landscape of these strained three-membered boron peroxides. Ongoing studies in our laboratories are exploring dioxaboriranes as versatile synthons for the construction of unprecedented main-group architectures and reactive intermediates. Declarations Acknowledgements We gratefully acknowledge financial support from the National Natural Science Foundation of China (22301030, 22350004, 22301122 and 22271132), the Dongguan Science and Technology of Social Development Program (No. 20231800940612), Guangdong Basic and Applied Basic Research Foundation (2024A1515010842), the Shenzhen Science and Technology Program (KQTD20240729102027009) and Guangdong Innovation and Entrepreneurial Research Team Program (2021ZT09C278). We also acknowledge the assistance of SUSTech Core Research Facilities. The theoretical work was supported by Song-Shan Lake HPC Center (SSL-HPC) at Great Bay University and the Center for Computational Science and Engineering at Southern University of Science and Technology. References Fan, X.; Fu, Q.; Liu, G.; Jia, H.; Dong, X.; Li, Y.-F.; Cui, S. Applying Molecular Oxygen for Organic Pollutant Degradation: Strategies, Mechanisms, and Perspectives. Environ. Sci. Ecotechnol. 2024 , 22 , 100469. (a) Li, X.; Gao, J.; Wu, C.; Wang, C.; Zhang, R.; He, J.; Xia, Z. J.; Joshi, N.; Karp, J. M.; Kuai, R. Precise Modulation and Use of Reactive Oxygen Species for Immunotherapy. Sci. Adv. 2024 , 10 , eadl0479. (b) Sies, H.; Jones, D. P. Reactive Oxygen Species (ROS) as Pleiotropic Physiological Signalling Agents. Nat. Rev. Mol. Cell Biol. 2020 , 21 , 363−383. Wang, R.; Dai, J.; Zhao, L.; Hu, Z.; Chen, C.-T.; Kuo, C.-Y.; Zhan, G.; Shi, Y.; Wang, J.; Zou, Y.; Xu, M.; Zou, X.; Zheng, Q.; Zhou, B.; Wang, K.; Zhao, R.; Zhang, Y.; Shen, Y.; Yao, Y.; Zhang, L. Compressive-Strained Rutile TiO 2 Enables O 2 Mono-Hydrogenation for Singlet Oxygen Electrosynthesis. Nat. Synth. 2025 , 4 , 754−764. (a) Wen, Y.; Yan, J.; Yang, B.; Zhuang, Z.; Yu, Y. Reactive Oxygen Species on Transition Metal-Based Catalysts for Sustainable Environmental Applications. J. Mater. Chem. A 2022 , 10 , 19184−19210. (b) Hong, S.; Lee, Y.-M.; Ray, K.; Nam, W. Dioxygen Activation Chemistry by Synthetic Mononuclear Nonheme Iron, Copper and Chromium Complexes. Coord. Chem. Rev. 2017 , 334 , 25−42. (a) Carsch, K. M.; Iliescu, A.; McGillicuddy, R. D.; Mason, J. A.; Betley, T. A. Reversible Scavenging of Dioxygen from Air by a Copper Complex. J. Am. Chem. Soc. 2021 , 143 , 18346−18352. (b) Montemore, M. M.; van Spronsen, M. A.; Madix, R. J.; Friend, C. M. O 2 Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts. Chem. Rev. 2018 , 118 , 2816−2862. (a) Saito, M.; Tokitoh, N.; Okazaki, R. Main Group Analogs of Dichalcogeniranes. Eur. J. Inorg. Chem. 2024 , 27 , e202300679. (b) Bach, R. D.; Andres, J. L.; Owensby, A. L.; Schlegel, H. B.; McDouall, J. J. W. Electronic Structure and Reactivity of Dioxirane and Carbonyl Oxide. J. Am. Chem. Soc. 1992 , 114 , 7207−7217. (c) Kraka, E.; Konkoli, Z.; Cremer, D.; Fowler, J.; Schaefer, H. F. Difluorodioxirane: An Unusual Cyclic Peroxide. J. Am. Chem. Soc. 1996 , 118 , 10595−10608. Sander, W.; Schroeder, K.; Muthusamy, S.; Kirschfeld, A.; Kappert, W.; Boese, R.; Kraka, E.; Sosa, C.; Cremer, D. Dimesityldioxirane. J. Am. Chem. Soc. 1997 , 119 , 7265−7270. Su, Y.; Kinjo, R. Small Molecule Activation by Boron-containing Heterocycles. Chem. Soc. Rev. 2019 , 48 , 3613−3659. Zhang, C.; Wang, J.; McMillion, N. D.; Deng, C.-L.; Gilliard, R. J.; Cummins, C. C. Reactions of Diazoboranes with Oxygen Enables the Synthesis and Isolation of Dioxaboriranes. Nat. Chem. 2026 , DOI:10.1038/s41557-41026-02120-x. Porcel, S.; Bouhadir, G.; Saffon, N.; Maron, L.; Bourissou, D. Reaction of Singlet Dioxygen with Phosphine–Borane Derivatives: From Transient Phosphine Peroxides to Crystalline Peroxoboronates. Angew. Chem. Int. Ed. 2010 , 49 , 6186−6189. (a) Henthorn, J. T.; Lin, S.; Agapie, T. Combination of Redox-Active Ligand and Lewis Acid for Dioxygen Reduction with π-Bound Molybdenum−Quinonoid Complexes. J. Am. Chem. Soc. 2015 , 137 , 1458−1464. (b) Henthorn, J. T.; Agapie, T. Dioxygen Reactivity with a Ferrocene–Lewis Acid Pairing: Reduction to a Boron Peroxide in the Presence of Tris(pentafluorophenyl)borane. Angew. Chem. Int. Ed. 2014 , 53 , 12893−12896. (a) Tao, X.; Daniliuc, C. G.; Janka, O.; Pöttgen, R.; Knitsch, R.; Hansen, M. R.; Eckert, H.; Lübbesmeyer, M.; Studer, A.; Kehr, G.; Erker, G. Reduction of Dioxygen by Radical/B( p -C 6 F 4 X) 3 Pairs to Give Isolable Bis(borane)superoxide Compounds. Angew. Chem. Int. Ed. 2017 , 56 , 16641−16644. (b) Wang, T.; Kehr, G.; Liu, L.; Grimme, S.; Daniliuc, C. G.; Erker, G. Selective Oxidation of an Active Intramolecular Amine/Borane Frustrated Lewis Pair with Dioxygen. J. Am. Chem. Soc. 2016 , 138 , 4302−4305. (a) Wang, B.; Kinjo, R. Boron-Based Stepwise Dioxygen Activation with 1,4,2,5-Diazadiborinine. Chem. Sci. 2019 , 10 , 2088−2092. (b) Dietz, M.; Arrowsmith, M.; Gärtner, A.; Radacki, K.; Bertermann, R.; Braunschweig, H. Harnessing the Electronic Differences between CAAC-Stabilised 1,4-Diborabenzene and 9,10-Diboraanthracene for Synthesis. Chem. Commun. 2021 , 57 , 13526−13529. (c) Taylor, J. W.; McSkimming, A.; Guzman, C. F.; Harman, W. H. N-Heterocyclic Carbene-Stabilized Boranthrene as a Metal-Free Platform for the Activation of Small Molecules. J. Am. Chem. Soc. 2017 , 139 , 11032−11035. Fan, J.; Pan, S.; Yao, S.; Ding, C.; Frenking, G.; Driess, M. From Bis(borylene)-Substituted Xanthenes as Reactive Intermediates to Diboraoxirane Complexes. J. Am. Chem. Soc. 2025 , 147 , 6925−6933. (a) Wood, T. K.; Piers, W. E.; Keay, B. A.; Parvez, M. 9-Boraanthracene Derivatives Stabilized by N-Heterocyclic Carbenes. Angew. Chem. Int. Ed. 2009 , 48 , 4009−4012. (b) Kong, L.; Lu, W.; Li, Y.; Ganguly, R.; Kinjo, R. Azaborabutadienes: Synthesis by Metal-Free Carboboration of Nitriles and Utility as Building Blocks for B,N-Heterocycles. Angew. Chem. Int. Ed. 2016 , 55 , 14718−14722. (c) Tsurumaki, E.; Sung, J.; Kim, D.; Osuka, A. Stable Boron Peroxides with a Subporphyrinato Ligand. Angew. Chem. Int. Ed. 2016 , 55 , 2596−2599. (a) Chen, C.; Daniliuc, C. G.; Mück-Lichtenfeld, C.; Kehr, G.; Erker, G. A BH Borenium-Derived Thioxoborane, Its Persulfide, and Their Li + -Induced Reactions with Alkynes and with Carbon Dioxide. J. Am. Chem. Soc. 2020 , 142 , 19763−19771. (b) Liu, S.; Légaré, M.-A.; Hofmann, A.; Braunschweig, H. A Boradiselenirane and a Boraditellurirane: Isolable Heavy Analogs of Dioxiranes and Dithiiranes. J. Am. Chem. Soc. 2018 , 140 , 11223−11226. (c) Chen, P.; Cui, C. Isolable Boron Persulfide: Activation of Elemental Sulfur with a 2‐Chloro‐Azaborolyl Anion. Chem. Eur. J. 2016 , 22 , 2902−2905. (d) Liu, S.; Légaré, M.-A.; Hofmann, A.; Rempel, A.; Hagspiel, S.; Braunschweig, H. Synthesis of Unsymmetrical B 2 E 2 and B 2 E 3 Heterocycles by Borylene Insertion into Boradichalcogeniranes. Chem. Sci. 2019 , 10 , 4662−4666. Xiong, Y.; Yao, S.; Müller, R.; Kaupp, M.; Driess, M. From Silicon(II)-Based Dioxygen Activation to Adducts of Elusive Dioxasiliranes and Sila-ureas Stable at Room Temperature. Nat. Chem. 2010 , 2 , 577−580. Nakamoto, M.; Akiba, K.-y. Stable Dioxaphosphirane Species: Facile Formation by Reaction of 10-P-4 1 Hypervalent Phosphoranide with Atmospheric Oxygen. J. Am. Chem. Soc. 1999 , 121 , 6958−6959. (a) Dahcheh, F.; Martin, D.; Stephan, D. W.; Bertrand, G. Synthesis and Reactivity of a CAAC-Aminoborylene Adduct: A Hetero-Allene or an Organoboron Isoelectronic with Singlet Carbenes. Angew. Chem. Int. Ed. 2014 , 53 , 13159−13163. (b) Li, J.; Lu, Z.; Liu, L. L. A Free Phosphaborene Stable at Room Temperature. J. Am. Chem. Soc. 2022 , 144 , 23691−23697. (a) Harvey, J. N. Understanding the Kinetics of Spin-Forbidden Chemical Reactions. Phys. Chem. Chem. Phys. 2007 , 9 , 331−343. (b) Tang, J.; Gao, X. J.; Tang, H.; Zeng, X. Dioxygen Activation with Stable N-heterocyclic Carbenes. Chem. Commun. 2019 , 55 , 1584−1587. Anulewicz-Ostrowska, R.; Luliński, S.; Serwatowski, J.; Suwińska, K. Diverse Reactivity of Dialkylaluminum Dimesitylboryloxides [(μ-Mes 2 BO)AlR 2 ] 2 . Synthetic and Structural Study. Inorg. Chem. 2000 , 39 , 5763−5767. (a) Loh, Y. K.; Porteous, K.; Fuentes, M. Á.; Do, D. C. H.; Hicks, J.; Aldridge, S. An Acid-Free Anionic Oxoborane Isoelectronic with Carbonyl: Facile Access and Transfer of a Terminal B=O Double Bond. J. Am. Chem. Soc. 2019 , 141 , 8073−8077. (b) Millet, C. R. P.; Willcox, D. R.; Nichol, G. S.; Anstöter, C. S.; Ingleson, M. J. A Base-Free Two-Coordinate Oxoborane. Angew. Chem. Int. Ed. 2025 , 64 , e202419094. (c) Wang, H.; Zhang, J.; Yang, J.; Xie, Z. Synthesis, Structure, and Reactivity of Acid-Free Neutral Oxoborane. Angew. Chem. Int. Ed. 2021 , 60 , 19008−19012. Schemes Schemes 1 and 2 are available in the Supplementary Files section Additional Declarations The authors declare no competing interests. Supplementary Files SupportingInformation.pdf Schemes.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9677735","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":638118101,"identity":"3f59f15b-3450-4a72-856a-8992ecf60915","order_by":0,"name":"Guanrong Chen","email":"","orcid":"","institution":"SUSTech","correspondingAuthor":false,"prefix":"","firstName":"Guanrong","middleName":"","lastName":"Chen","suffix":""},{"id":638119565,"identity":"c8a9e364-72ad-4d50-adb2-4cd9e07f4ea7","order_by":1,"name":"Zhaoyang Liu","email":"","orcid":"","institution":"Great Bay University","correspondingAuthor":false,"prefix":"","firstName":"Zhaoyang","middleName":"","lastName":"Liu","suffix":""},{"id":638119566,"identity":"57f287d3-dff9-4046-9ce2-1d3a6dc20f62","order_by":2,"name":"Jiancheng Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYBACPmaGBMYPFRAOMxAzNhDSwgbUwixxBsQiWguI4G0jSQs7w8MPkvPqEufPbz74uYDBRnbDAeZnDwg4LFmicNvhxA3H2JKlZzCkGW84wGZuQEBLGoPktgOJG9h4zJh5GIB6D/CwSRDUwjsH6LA2/m9ALf+J1dLAnNhwjIcNqOUAUVqSpSWOHTbecCzNWJrHINl45mE2M7xa+PnPJH78UFMnO7/58MPPPBV2sn3Hm5/h1cLAwJOAxAEFFTN+9UDAfoCgklEwCkbBKBjhAAB3yD8Mbx+YXwAAAABJRU5ErkJggg==","orcid":"","institution":"SUSTech","correspondingAuthor":true,"prefix":"","firstName":"Jiancheng","middleName":"","lastName":"Li","suffix":""},{"id":638119567,"identity":"5b03dc07-6229-49a9-9e97-b9e419543472","order_by":3,"name":"Liu Leo Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9UlEQVRIiWNgGAWjYBACPmYGxgMMDBY8DOwNEBEDIJbAp4WNmYEBqEWCh4EHSDEkEKOFAaIFiBKI1cLOY3DgQ4WEjMHN588kf/6wkTdnYD54m4fBLg+3w3gMDs44I8FjcDvHTJonIc1wZwNbsjUPQ3IxPi2HedvAWtikGRIOJxgc4AHqZTiQ2IBPy1+QlpvHn0n+SPgP1ML/jbAWRpCWGwxmEjwJB0C2sBHQwlZwsAfoF8kzOcbWPGnJhhsOsxlbzjFIxqmFn//wxgc/Kmzs+Y4ff3jzh42dvMHx5oc33lTY4dSCBTCDCAPi1Y+CUTAKRsEowAQAO3pMk/Hi5vsAAAAASUVORK5CYII=","orcid":"","institution":"SUSTech","correspondingAuthor":true,"prefix":"","firstName":"Liu","middleName":"Leo","lastName":"Liu","suffix":""},{"id":638119568,"identity":"ac80d898-8d26-4cdd-ab53-43d4177106f3","order_by":4,"name":"Hanqiang Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYBACAxCRAON9YDgAFyROC+MMorXAADMPMVrM2c8evPGg5o7dhuNnD7+2+XUnsYG9eZsEQ80dnFose/KSLRKOPUvecCYvzTq371liA8+xMgmGY89wO+xAjplEAtvhZDMgwzi353BigwRQhLHhMG4t598AtfwDagEyjC1BWuTfENByA2hmYtthO7MbOcaPGX6AbOEhpOWNsUVi3+EE+xtvzBh7G54Zt/GkFQN9h89hOYY3f3w7bC/Zn2P84cefO7L97Ic33vhQg1sLCEgAcWIDAwObBGMbkAQJJeDVANFiD8TMHxj+EFA6CkbBKBgFIxIAAOuEYZy9vn73AAAAAElFTkSuQmCC","orcid":"","institution":"Great Bay University","correspondingAuthor":true,"prefix":"","firstName":"Hanqiang","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2026-05-11 09:42:24","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-9677735/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9677735/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109097223,"identity":"35f7d918-1952-4626-a490-c87786756780","added_by":"auto","created_at":"2026-05-12 14:07:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":86807,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Acyclic and cyclic Ch\u003csub\u003e2\u003c/sub\u003e motifs. (b) Known examples of boron peroxides. (c) Nitrogen to oxygen exchange at diazoboranes. (d) Borylene activation of dioxygen (This work). CAAC = 1-(2,6-diisopropylphenyl)-3,3-diethyl-5,5-dimethylpyrrolidin-2-ylidene, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, Mes = 2,4,6-trimethylphenyl, I\u003csup\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sup\u003ePr\u003csub\u003e2\u003c/sub\u003e = 1,3-diisopropyl-4,5-dimethylimidazole-2-ylidene, Dmp = 2,6-dimesitylphenyl, SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene, Dur = 2,3,5,6-tetramethylphenyl\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/d77279adeebdbc60aa453e60.png"},{"id":109097571,"identity":"bb29ce09-2d7b-4cda-8978-5a6129534a86","added_by":"auto","created_at":"2026-05-12 14:09:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":71647,"visible":true,"origin":"","legend":"\u003cp\u003eSolid-state structures of \u003cstrong\u003e2\u003c/strong\u003e(a) and \u003cstrong\u003e3\u003c/strong\u003e(b). For clarity, the Dipp, ethyl and methyl groups are drawn in wireframe and hydrogen atoms are omitted in the structure. Anisotropic displacement ellipsoids are set at the 30% probability level.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/3d31d034ba16fb17c2f4b898.png"},{"id":109097580,"identity":"a16b6411-568e-4170-ace3-29f8749f7ba5","added_by":"auto","created_at":"2026-05-12 14:09:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":221535,"visible":true,"origin":"","legend":"\u003cp\u003eSelected IBOs of \u003cstrong\u003e3\u003c/strong\u003e. (a) combined lone-pair orbitals at O1 and O2 atoms in the B1−O1−O2 plane; (b) combined lone-pair orbitals at O1 and O2 atoms out of the B1−O1−O2 plane; (c) O1−O2 σ-bonding orbital; (d) combined B1−O1 and B1−O2 σ-bonding orbitals.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/89aa4fc24a0de5cd0297b78a.png"},{"id":109097394,"identity":"f8be0571-8525-4232-abd5-575c2bc78479","added_by":"auto","created_at":"2026-05-12 14:08:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":81592,"visible":true,"origin":"","legend":"\u003cp\u003eFree energy profile of dioxygen activation by borylene.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/568aa2dfc401888a76166755.png"},{"id":109097519,"identity":"ebc0f15a-37bd-4272-beca-292183c84fd7","added_by":"auto","created_at":"2026-05-12 14:08:47","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":80161,"visible":true,"origin":"","legend":"\u003cp\u003eSolid-state structures of \u003cstrong\u003e4\u003c/strong\u003e(a) and \u003cstrong\u003e5\u003c/strong\u003e(b). For clarity, the Dipp, OSO\u003csub\u003e2\u003c/sub\u003eCF\u003csub\u003e3\u003c/sub\u003e, ethyl and methyl moieties are drawn in wireframe and hydrogen atoms are omitted. Anisotropic displacement ellipsoids are set at the 30% probability level.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/f2618819ba2bdd95f5e9b2c0.png"},{"id":109204778,"identity":"613a1972-cd35-443e-aa16-9c088ef8706a","added_by":"auto","created_at":"2026-05-13 15:02:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":646783,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/444c74c5-e8c0-47ad-80fc-0d164223c12c.pdf"},{"id":109097393,"identity":"b10f9c41-d4b0-47e3-8953-2cd252c9175b","added_by":"auto","created_at":"2026-05-12 14:08:32","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2930052,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/749fc3281d2d56a306888be3.pdf"},{"id":109097225,"identity":"ea7dc023-168e-4ae7-9fd9-c0ee4ce9ea9a","added_by":"auto","created_at":"2026-05-12 14:07:38","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":78916,"visible":true,"origin":"","legend":"","description":"","filename":"Schemes.docx","url":"https://assets-eu.researchsquare.com/files/rs-9677735/v1/e9bff3fff974522cb97a719e.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eA Crystalline Dioxaborirane through Borylene Activation of Dioxygen\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Main Text","content":"\u003cp\u003eDioxygen (O\u003csub\u003e2\u003c/sub\u003e) activation has continued to attract considerable attention because of its critical importance across multiple fields. Reactive oxygen species (ROS) play indispensable roles in environmental remediation,\u003csup\u003e1\u003c/sup\u003e where their oxidative capacity is harnessed to degrade persistent pollutants, and in biological systems, where they function as regulated signaling mediators that control immunity and cellular metabolism.\u003csup\u003e2\u003c/sup\u003e Despite the abundance, environmental benignity, and intrinsic oxidizing capacity of molecular oxygen, its triplet ground state imposes a substantial kinetic barrier that limits its direct reaction with most organic substrates under ambient conditions.\u003csup\u003e3\u003c/sup\u003e Overcoming this constraint to access ROS, including singlet dioxygen (\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e), superoxide (O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026bull;\u0026minus;\u003c/sup\u003e), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), and hydroxyl radicals (\u0026bull;OH), has traditionally relied on transition-metal catalysts capable of promoting O\u003csub\u003e2\u003c/sub\u003e reduction and generating peroxide- or superoxide-derived intermediates.\u003csup\u003e4\u003c/sup\u003e Representative systems include metalloenzymes that transiently form reactive metal-oxygen species and metal-organic frameworks (MOFs) that facilitate reversible dioxygen binding and activation.\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eFor organic compounds containing an O\u003csub\u003e2\u003c/sub\u003e motif, the archetypal examples are dioxiranes and peroxides; however, these two classes of molecules are fundamentally distinct in their electronic structures (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). In acyclic organic peroxides, the O\u0026thinsp;\u0026minus;\u0026thinsp;O linkage is destabilized by repulsive interactions between the lone pairs of the two oxygen atoms. By contrast, cyclic dioxiranes impose a rigid three-membered-ring geometry that enforces close and nearly parallel alignment of oxygen lone pairs, thereby amplifying Pauli repulsion and ring strain.\u003csup\u003e6\u003c/sup\u003e Consequently, whereas many acyclic organic peroxides are isolable compounds, dioxiranes are generally encountered as highly reactive intermediates.\u003csup\u003e7\u003c/sup\u003e A similar distinction is apparent in boron\u0026minus;oxygen chemistry: although boron compounds have been extensively explored for dioxygen activation,\u003csup\u003e8\u003c/sup\u003e the resulting boron peroxide species are predominantly confined to acyclic architectures or embedded within five- or six-membered rings, rather than adopting highly strained dioxaborirane motifs.\u003csup\u003e9\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eEarly studies by Bourissou showed that peroxide compound \u003cb\u003eI\u003c/b\u003e could be generated from the reaction of phosphine\u0026minus;boronate complexes with singlet dioxygen.\u003csup\u003e10\u003c/sup\u003e Agapie demonstrated that related peroxide compound \u003cb\u003eII\u003c/b\u003e could be accessed through cooperative dioxygen activation involving a Lewis acidic borane and transition-metal reductants.\u003csup\u003e11\u003c/sup\u003e Subsequent work by Erker led to isolable bis(borane) superoxide compounds \u003cb\u003eIII\u003c/b\u003e using radical/borane pairs.\u003csup\u003e12\u003c/sup\u003e Piers, Kinjo and Harman further established that dual boron centers embedded in aromatic frameworks are capable of activating O\u003csub\u003e2\u003c/sub\u003e to form boron peroxides \u003cb\u003eIV\u003c/b\u003e\u0026thinsp;\u0026minus;\u0026thinsp;\u003cb\u003eV\u003c/b\u003e.\u003csup\u003e13\u003c/sup\u003e This cooperative dual-boron-center strategy was reinforced by Driess and Frenking, who found that diboraoxiranes reacted with O\u003csub\u003e2\u003c/sub\u003e to afford diboraperoxides \u003cb\u003eVI\u003c/b\u003e.\u003csup\u003e14\u003c/sup\u003e Collectively, these well-defined bis(borane) superoxide and related peroxide species predominantly rely on dual active centers \u003cb\u003eVII\u003c/b\u003e\u0026minus;\u003cb\u003eVIII\u003c/b\u003e.\u003csup\u003e15\u003c/sup\u003e In contrast, the development of side-on peroxo species, namely dioxaboriranes, based on a single boron atom has lagged significantly behind. This gap is particularly evident in the chemistry of three-membered main-group heterocycles, where research efforts have thus far focused mainly on heavier chalcogen analogues, including dithiaboriranes, diselenaboriranes, and ditelluraboriranes, which are typically prepared from borylene or boron anion precursors.\u003csup\u003e6a, 14, 16\u003c/sup\u003e During the preparation of this manuscript, only one dioxaborirane was recently described by Cummins and Gilliard through the reaction of diazoboranes with dioxygen, which proceeds through nitrogen-to-oxygen exchange at the boron center rather than through a borylene intermediate (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003csup\u003e9\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCremer reported the synthesis of a dioxirane from the reaction of a transient triplet carbene with O\u003csub\u003e2\u003c/sub\u003e,\u003csup\u003e7\u003c/sup\u003e while Driess demonstrated that carbene-supported silylenes similarly reacted with O\u003csub\u003e2\u003c/sub\u003e to afford dioxasiliranes.\u003csup\u003e17\u003c/sup\u003e Phosphadioxiranes have also been obtained from the reaction of hypervalent phosphoranides with dioxygen.\u003csup\u003e18\u003c/sup\u003e Inspired by these precedents, we hypothesized that direct borylene activation of O\u003csub\u003e2\u003c/sub\u003e could provide a promising route to the long-sought synthesis of highly reactive dioxaboriranes (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Herein, we report the synthesis and single-crystal X-ray characterization of a dioxaborirane species, as well as its O\u0026thinsp;\u0026minus;\u0026thinsp;O bond cleavage in the presence of Lewis acids.\u003c/p\u003e \u003cp\u003eTo stabilize the reactive BO\u003csub\u003e2\u003c/sub\u003e three-member ring, a sterically encumbered environment was introduced around boron, leading to the synthesis of cyclic (alkyl)(amino)carbene (CAAC)-stabilized iminoborylene \u003cb\u003e2\u003c/b\u003e, which can be viewed as BN‑embedded heterocumulenes.\u003csup\u003e19\u003c/sup\u003e Borylene \u003cb\u003e2\u003c/b\u003e reacted smoothly with dioxygen to afford dioxaborirane \u003cb\u003e3\u003c/b\u003e at \u0026minus;\u0026thinsp;20\u0026deg;C (Scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This conversion was clearly indicated by a shift in the \u003csup\u003e11\u003c/sup\u003eB{\u003csup\u003e1\u003c/sup\u003eH} NMR signal from 57.6 ppm to \u0026minus;\u0026thinsp;2.8 ppm. Subsequent concentration of the reaction mixture and cooling to \u0026minus;\u0026thinsp;20\u0026deg;C yielded yellow crystals of \u003cb\u003e3\u003c/b\u003e, which decomposed readily at room temperature. The time-dependent \u003csup\u003e1\u003c/sup\u003eH NMR in C\u003csub\u003e6\u003c/sub\u003eD\u003csub\u003e6\u003c/sub\u003e showed that the half-life of \u003cb\u003e3\u003c/b\u003e at room temperature is approximately 10 hours (Figure S17 and S18). Single-crystal structural analysis reveals that compound \u003cb\u003e3\u003c/b\u003e contains a three-membered ring composed of one boron and two oxygen atoms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The O1\u0026thinsp;\u0026minus;\u0026thinsp;B1\u0026minus;O2, B1\u0026thinsp;\u0026minus;\u0026thinsp;O1\u0026minus;O2, and B1\u0026thinsp;\u0026minus;\u0026thinsp;O2\u0026minus;O1 bond angles are 64.0(8)\u0026deg;, 57.3(5)\u0026deg; and 58.6(3)\u0026deg;, respectively, which reflect the significant ring strain. The B1\u0026thinsp;\u0026minus;\u0026thinsp;O1 and B1\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond lengths (1.473(6) \u0026Aring; and 1.453(6) \u0026Aring;, respectively) resemble those found in anionic (1.471(1) \u0026Aring; and 1.468(1) \u0026Aring;) and neutral dioxaborirane (1.443(1) \u0026Aring; and 1.458(1) \u0026Aring;).\u003csup\u003e9\u003c/sup\u003e Meanwhile, the O1\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond distance of 1.553(5) \u0026Aring; is notably longer than those (1.280(4)\u0026thinsp;\u0026minus;\u0026thinsp;1.507(4) \u0026Aring;) reported bridging O\u003csub\u003e2\u003c/sub\u003e systems\u003csup\u003e11b, 12a, 13\u0026ndash;15, 15c\u003c/sup\u003e and similar to that in dioxaboriranes (1.530(1) \u0026Aring; and 1.549(2) \u0026Aring;)\u003csup\u003e9\u003c/sup\u003e and dioxasiliranes (1.547(3) \u0026Aring;)\u003csup\u003e17\u003c/sup\u003e. The elongation of O1\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond, compared to that in bridging B\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;O\u0026thinsp;\u0026minus;\u0026thinsp;E complexes, is likely attributed to the combined effects of strong Pauli repulsion between oxygen lone pairs and inherent ring strain of three-membered ring (Figure S21).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe bonding and electronic structure of \u003cb\u003e3\u003c/b\u003e were further elucidated through density functional theory (DFT) calculations, complemented by frontier molecular orbital (FMO) and natural bond orbital (NBO) examinations. The intrinsic bond orbital (IBO) results confirm well-defined σ-bonding orbitals corresponding to the B1\u0026thinsp;\u0026minus;\u0026thinsp;O1, B1\u0026thinsp;\u0026minus;\u0026thinsp;O2, and O1\u0026thinsp;\u0026minus;\u0026thinsp;O2 interactions (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Each oxygen atom bears a predominantly nonbonding lone pair orbital (96.1% on O1 and 95.4% on O2) oriented out of the B1\u0026thinsp;\u0026minus;\u0026thinsp;O1\u0026minus;O2 plane. This highly localized electron density generates substantial Pauli repulsion, which contributes to the observed elongation of the O\u0026thinsp;\u0026minus;\u0026thinsp;O bond. Similarly, the in-plane lone pairs are even more localized with 98.8% of the density confined to the oxygen atoms. Further support comes from the Wiberg bond index of 0.97 for the O1\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond. Additionally, NBO charge analysis reveals considerable charge separation with a boron charge of +\u0026thinsp;0.81 a.u. and oxygen charges of \u0026minus;\u0026thinsp;0.49 a.u. and \u0026minus;\u0026thinsp;0.48 a.u., respectively (Figure S24).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAlthough several reports have documented dioxygen activation by boron-containing compounds,\u003csup\u003e10\u0026ndash;15\u003c/sup\u003e the detailed reaction mechanism still remains inadequately explored, largely due to the spin-forbidden nature of triplet dioxygen in such processes.\u003csup\u003e9, 20\u003c/sup\u003e To elucidate the mechanism of dioxygen activation by borylene, we conducted density functional theory (DFT) calculations to calculate the free energy (ΔG) and electronic energy (ΔE) using the reaction of \u003cb\u003e2\u003c/b\u003e with \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e as a model. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, this process begins with borylene \u003cb\u003e2\u003c/b\u003e donating an electron to \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e. This step proceeds via transition state \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e, which surmounts an activation free energy of 12.6 kcal/mol to form a triplet η\u003csup\u003e1\u003c/sup\u003e-O\u003csub\u003e2\u003c/sub\u003e-type superoxide intermediate \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT1\u003c/b\u003e. This dioxygen addition step (\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e) is identified as rate-determining step, and its relatively low activation barrier is consistent with the experimentally observed rapid reaction at low temperature. Subsequently, \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT2\u003c/b\u003e was successfully located by performing a relaxed scan of the potential energy surface (PES), which is 2.7 kcal/mol more stable than \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT1\u003c/b\u003e. Minimum energy crossing point (MECP) calculations indicate that this system can undergo intersystem crossing from \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT2\u003c/b\u003e to a more stable singlet intermediate \u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT3\u003c/b\u003e with a minimal energy barrier (ΔE) of 0.7 kcal/mol. Finally, \u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eINT3\u003c/b\u003e overcomes a relatively low barrier (ΔG) of 8.5 kcal/mol to rearrange to dioxaborirane.\u003c/p\u003e \u003cp\u003eTo further characterize the electronic interaction between borylene \u003cb\u003e2\u003c/b\u003e and dioxygen, the relationship between the C2\u0026thinsp;\u0026minus;\u0026thinsp;B1\u0026minus;N1 bending angle and energy was evaluated, and the corresponding torsional profile is plotted in Figure S26. This scan reveals that bending C2\u0026thinsp;\u0026minus;\u0026thinsp;B1\u0026minus;N1 angle to 154.4\u0026deg; in the resulting bent structure 2b, which closely resembles that (155.5\u0026deg;) in \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e, requires only a minor energetic cost of 2.3 kcal/mol. This bent geometry endows \u003cb\u003e2b\u003c/b\u003e with pronounced electrophilicity by aligning the formally vacant p orbital on boron with sp\u003csup\u003e2\u003c/sup\u003e-hybridization, thereby lowering its energy.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eConsequently, the relevant unoccupied orbital on boron drops from LUMO\u0026thinsp;+\u0026thinsp;9 (2.06 eV) to LUMO\u0026thinsp;+\u0026thinsp;7 (1.55 eV), as illustrated in Figure S27. Then, the frontier molecular orbitals of \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e were examined. The singly occupied p orbital of the borylene boron atom in \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e is reflected in the SOMO. Meanwhile, the overlap between the π\u003csub\u003e2pz\u003c/sub\u003e\u003csup\u003e*\u003c/sup\u003e orbitals of \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e and the π orbital of the Dipp-arene ring appears in the SOMO\u0026thinsp;\u0026minus;\u0026thinsp;1 (Figure S28). This indicates electron transfer from the boron atom of borylene to the π\u003csub\u003e2py\u003c/sub\u003e* orbitals of \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e, in contrast to the formation of dioxaboriranes by Cummins and Gilliard, in which free boryl anion or borylene intermediates are excluded. To better understand bonding interaction between borylene \u003cb\u003e2\u003c/b\u003e and dioxygen, a comprehensive analysis by the extended transition state-natural orbitals for chemical valence (ETS-NOCV) was carried out. Figure S29 shows that the differential densities associated with these interactions dominate the bonding between \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e and borylene unit in \u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003eTS1\u003c/b\u003e. The charge flow direction from blue to red regions indicates electron density transfer from the doubly occupied p orbital of borylene boron into the π\u003csub\u003e2py\u003c/sub\u003e\u003csup\u003e*\u003c/sup\u003e orbitals of \u003csup\u003e3\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e with an associated energy of \u0026minus;\u0026thinsp;23.53 kcal/mol.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe paramount importance of the O\u0026thinsp;\u0026minus;\u0026thinsp;O bond strength across diverse chemical processes motivates our investigation into its dissociation (Scheme \u003cspan refid=\"Sch2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Compound \u003cb\u003e3\u003c/b\u003e demonstrated notable reactivity toward AlMe\u003csub\u003e3\u003c/sub\u003e at \u0026minus;\u0026thinsp;20\u0026deg;C, cleanly yielding an alumoxane complex \u003cb\u003e4\u003c/b\u003e. The molecular structure of \u003cb\u003e4\u003c/b\u003e features a B\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;Al\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;Al bridging motif (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). In complex \u003cb\u003e4\u003c/b\u003e, the Al1\u0026thinsp;\u0026minus;\u0026thinsp;O1 and B1\u0026thinsp;\u0026minus;\u0026thinsp;O1 bond lengths of 1.775(2) \u0026Aring; and 1.338(2) \u0026Aring;, respectively, fall within the range reported for related compounds.\u003csup\u003e21\u003c/sup\u003e The Al1\u0026thinsp;\u0026minus;\u0026thinsp;O2 and Al2\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond lengths of 1.843(2) \u0026Aring; and 1.868(2) \u0026Aring; are notably longer than the Al1\u0026thinsp;\u0026minus;\u0026thinsp;O1 bond length of 1.775(2) \u0026Aring;. The controlled oxygen atom transfer by AlMe\u003csub\u003e3\u003c/sub\u003e provides a model for the interaction of reactive peroxide species with main-group Lewis acids.\u003c/p\u003e \u003cp\u003eUpon treatment with 2 equiv. of AgOTf at \u0026minus;\u0026thinsp;20\u0026deg;C, compound \u003cb\u003e3\u003c/b\u003e was smoothly converted to complex \u003cb\u003e5\u003c/b\u003e. X-ray diffraction analysis of \u003cb\u003e5\u003c/b\u003e clearly revealed a B\u0026thinsp;=\u0026thinsp;O double bond (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). In the solid state, two independent Ag⁺ ions are present. Ag1 is bridged by two triflate anions and further coordinated by the B\u0026thinsp;=\u0026thinsp;O group and a Dipp-arene ring, whereas Ag2 is also bridged by two triflate anions and additionally interacts with B\u0026thinsp;=\u0026thinsp;O and C\u0026thinsp;=\u0026thinsp;N moieties. For complex \u003cb\u003e5\u003c/b\u003e, the B1\u0026thinsp;\u0026minus;\u0026thinsp;O2 bond lengths of 1.294(8) \u0026Aring; are in the range of those in previously reported oxoborane compounds.\u003csup\u003e22\u003c/sup\u003e The reaction of \u003cb\u003e3\u003c/b\u003e with AgOTf cleanly affords an oxoborane\u0026minus;silver complex \u003cb\u003e5\u003c/b\u003e, highlighting silver(I) as an effective reagent for accessing Lewis-acid-stabilized oxoborane fragments.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn summary, this work has established direct borylene activation of triplet dioxygen for accessing a dioxaborirane and reveals Lewis-acid-induced O\u0026ndash;O bond cleavage, thereby expanding the reactivity landscape of these strained three-membered boron peroxides. Ongoing studies in our laboratories are exploring dioxaboriranes as versatile synthons for the construction of unprecedented main-group architectures and reactive intermediates.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eWe gratefully acknowledge financial support from the National Natural Science Foundation of China (22301030, 22350004, 22301122 and 22271132), the Dongguan Science and Technology of Social Development Program (No. 20231800940612), Guangdong Basic and Applied Basic Research Foundation (2024A1515010842), the Shenzhen Science and Technology Program (KQTD20240729102027009) and Guangdong Innovation and Entrepreneurial Research Team Program (2021ZT09C278). We also acknowledge the assistance of SUSTech Core Research Facilities. The theoretical work was supported by Song-Shan Lake HPC Center (SSL-HPC) at Great Bay University and the Center for Computational Science and Engineering at Southern University of Science and Technology.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFan, X.; Fu, Q.; Liu, G.; Jia, H.; Dong, X.; Li, Y.-F.; Cui, S. Applying Molecular Oxygen for Organic Pollutant Degradation: Strategies, Mechanisms, and Perspectives. \u003cem\u003eEnviron. Sci. Ecotechnol. \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e22\u003c/em\u003e, 100469.\u003c/li\u003e\n\u003cli\u003e(a) Li, X.; Gao, J.; Wu, C.; Wang, C.; Zhang, R.; He, J.; Xia, Z. J.; Joshi, N.; Karp, J. M.; Kuai, R. Precise Modulation and Use of Reactive Oxygen Species for Immunotherapy. \u003cem\u003eSci. Adv. \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e, eadl0479. (b) Sies, H.; Jones, D. P. Reactive Oxygen Species (ROS) as Pleiotropic Physiological Signalling Agents. \u003cem\u003eNat. Rev. Mol. Cell Biol. \u003c/em\u003e\u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e21\u003c/em\u003e, 363\u0026minus;383.\u003c/li\u003e\n\u003cli\u003eWang, R.; Dai, J.; Zhao, L.; Hu, Z.; Chen, C.-T.; Kuo, C.-Y.; Zhan, G.; Shi, Y.; Wang, J.; Zou, Y.; Xu, M.; Zou, X.; Zheng, Q.; Zhou, B.; Wang, K.; Zhao, R.; Zhang, Y.; Shen, Y.; Yao, Y.; Zhang, L. Compressive-Strained Rutile TiO\u003csub\u003e2\u003c/sub\u003e Enables O\u003csub\u003e2\u003c/sub\u003e Mono-Hydrogenation for Singlet Oxygen Electrosynthesis. \u003cem\u003eNat. Synth. \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e4\u003c/em\u003e, 754\u0026minus;764.\u003c/li\u003e\n\u003cli\u003e(a) Wen, Y.; Yan, J.; Yang, B.; Zhuang, Z.; Yu, Y. Reactive Oxygen Species on Transition Metal-Based Catalysts for Sustainable Environmental Applications. \u003cem\u003eJ. Mater. Chem. A \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e, 19184\u0026minus;19210. (b) Hong, S.; Lee, Y.-M.; Ray, K.; Nam, W. Dioxygen Activation Chemistry by Synthetic Mononuclear Nonheme Iron, Copper and Chromium Complexes. \u003cem\u003eCoord. Chem. Rev. \u003c/em\u003e\u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e334\u003c/em\u003e, 25\u0026minus;42.\u003c/li\u003e\n\u003cli\u003e(a) Carsch, K. M.; Iliescu, A.; McGillicuddy, R. D.; Mason, J. A.; Betley, T. A. Reversible Scavenging of Dioxygen from Air by a Copper Complex. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e143\u003c/em\u003e, 18346\u0026minus;18352. (b) Montemore, M. M.; van Spronsen, M. A.; Madix, R. J.; Friend, C. M. O\u003csub\u003e2\u003c/sub\u003e Activation by Metal Surfaces: Implications for Bonding and Reactivity on Heterogeneous Catalysts. \u003cem\u003eChem. Rev. \u003c/em\u003e\u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e118\u003c/em\u003e, 2816\u0026minus;2862.\u003c/li\u003e\n\u003cli\u003e(a) Saito, M.; Tokitoh, N.; Okazaki, R. Main Group Analogs of Dichalcogeniranes. \u003cem\u003eEur. J. Inorg. Chem. \u003c/em\u003e\u003cstrong\u003e2024\u003c/strong\u003e, \u003cem\u003e27\u003c/em\u003e, e202300679. (b) Bach, R. D.; Andres, J. L.; Owensby, A. L.; Schlegel, H. B.; McDouall, J. J. W. Electronic Structure and Reactivity of Dioxirane and Carbonyl Oxide. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e1992\u003c/strong\u003e, \u003cem\u003e114\u003c/em\u003e, 7207\u0026minus;7217. (c) Kraka, E.; Konkoli, Z.; Cremer, D.; Fowler, J.; Schaefer, H. F. Difluorodioxirane:\u0026thinsp; An Unusual Cyclic Peroxide. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e1996\u003c/strong\u003e, \u003cem\u003e118\u003c/em\u003e, 10595\u0026minus;10608.\u003c/li\u003e\n\u003cli\u003eSander, W.; Schroeder, K.; Muthusamy, S.; Kirschfeld, A.; Kappert, W.; Boese, R.; Kraka, E.; Sosa, C.; Cremer, D. Dimesityldioxirane. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e1997\u003c/strong\u003e, \u003cem\u003e119\u003c/em\u003e, 7265\u0026minus;7270.\u003c/li\u003e\n\u003cli\u003eSu, Y.; Kinjo, R. Small Molecule Activation by Boron-containing Heterocycles. \u003cem\u003eChem. Soc. Rev. \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e48\u003c/em\u003e, 3613\u0026minus;3659.\u003c/li\u003e\n\u003cli\u003eZhang, C.; Wang, J.; McMillion, N. D.; Deng, C.-L.; Gilliard, R. J.; Cummins, C. C. Reactions of Diazoboranes with Oxygen Enables the Synthesis and Isolation of Dioxaboriranes. \u003cem\u003eNat. Chem. \u003c/em\u003e\u003cstrong\u003e2026\u003c/strong\u003e, DOI:10.1038/s41557-41026-02120-x.\u003c/li\u003e\n\u003cli\u003ePorcel, S.; Bouhadir, G.; Saffon, N.; Maron, L.; Bourissou, D. Reaction of Singlet Dioxygen with Phosphine\u0026ndash;Borane Derivatives: From Transient Phosphine Peroxides to Crystalline Peroxoboronates. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2010\u003c/strong\u003e, \u003cem\u003e49\u003c/em\u003e, 6186\u0026minus;6189.\u003c/li\u003e\n\u003cli\u003e(a) Henthorn, J. T.; Lin, S.; Agapie, T. Combination of Redox-Active Ligand and Lewis Acid for Dioxygen Reduction with \u0026pi;-Bound Molybdenum\u0026minus;Quinonoid Complexes. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2015\u003c/strong\u003e, \u003cem\u003e137\u003c/em\u003e, 1458\u0026minus;1464. (b) Henthorn, J. T.; Agapie, T. Dioxygen Reactivity with a Ferrocene\u0026ndash;Lewis Acid Pairing: Reduction to a Boron Peroxide in the Presence of Tris(pentafluorophenyl)borane. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e53\u003c/em\u003e, 12893\u0026minus;12896.\u003c/li\u003e\n\u003cli\u003e(a) Tao, X.; Daniliuc, C. G.; Janka, O.; P\u0026ouml;ttgen, R.; Knitsch, R.; Hansen, M. R.; Eckert, H.; L\u0026uuml;bbesmeyer, M.; Studer, A.; Kehr, G.; Erker, G. Reduction of Dioxygen by Radical/B(\u003cem\u003ep\u003c/em\u003e-C\u003csub\u003e6\u003c/sub\u003eF\u003csub\u003e4\u003c/sub\u003eX)\u003csub\u003e3\u003c/sub\u003e Pairs to Give Isolable Bis(borane)superoxide Compounds. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e56\u003c/em\u003e, 16641\u0026minus;16644. (b) Wang, T.; Kehr, G.; Liu, L.; Grimme, S.; Daniliuc, C. G.; Erker, G. Selective Oxidation of an Active Intramolecular Amine/Borane Frustrated Lewis Pair with Dioxygen. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e138\u003c/em\u003e, 4302\u0026minus;4305.\u003c/li\u003e\n\u003cli\u003e(a) Wang, B.; Kinjo, R. Boron-Based Stepwise Dioxygen Activation with 1,4,2,5-Diazadiborinine. \u003cem\u003eChem. Sci. \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e, 2088\u0026minus;2092. (b) Dietz, M.; Arrowsmith, M.; G\u0026auml;rtner, A.; Radacki, K.; Bertermann, R.; Braunschweig, H. Harnessing the Electronic Differences between CAAC-Stabilised 1,4-Diborabenzene and 9,10-Diboraanthracene for Synthesis. \u003cem\u003eChem. Commun. \u003c/em\u003e\u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e57\u003c/em\u003e, 13526\u0026minus;13529. (c) Taylor, J. W.; McSkimming, A.; Guzman, C. F.; Harman, W. H. N-Heterocyclic Carbene-Stabilized Boranthrene as a Metal-Free Platform for the Activation of Small Molecules. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2017\u003c/strong\u003e, \u003cem\u003e139\u003c/em\u003e, 11032\u0026minus;11035.\u003c/li\u003e\n\u003cli\u003eFan, J.; Pan, S.; Yao, S.; Ding, C.; Frenking, G.; Driess, M. From Bis(borylene)-Substituted Xanthenes as Reactive Intermediates to Diboraoxirane Complexes. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e147\u003c/em\u003e, 6925\u0026minus;6933.\u003c/li\u003e\n\u003cli\u003e(a) Wood, T. K.; Piers, W. E.; Keay, B. A.; Parvez, M. 9-Boraanthracene Derivatives Stabilized by N-Heterocyclic Carbenes. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2009\u003c/strong\u003e, \u003cem\u003e48\u003c/em\u003e, 4009\u0026minus;4012. (b) Kong, L.; Lu, W.; Li, Y.; Ganguly, R.; Kinjo, R. Azaborabutadienes: Synthesis by Metal-Free Carboboration of Nitriles and Utility as Building Blocks for B,N-Heterocycles. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e55\u003c/em\u003e, 14718\u0026minus;14722. (c) Tsurumaki, E.; Sung, J.; Kim, D.; Osuka, A. Stable Boron Peroxides with a Subporphyrinato Ligand. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e55\u003c/em\u003e, 2596\u0026minus;2599.\u003c/li\u003e\n\u003cli\u003e(a) Chen, C.; Daniliuc, C. G.; M\u0026uuml;ck-Lichtenfeld, C.; Kehr, G.; Erker, G. A BH Borenium-Derived Thioxoborane, Its Persulfide, and Their Li\u003csup\u003e+\u003c/sup\u003e-Induced Reactions with Alkynes and with Carbon Dioxide. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2020\u003c/strong\u003e, \u003cem\u003e142\u003c/em\u003e, 19763\u0026minus;19771. (b) Liu, S.; L\u0026eacute;gar\u0026eacute;, M.-A.; Hofmann, A.; Braunschweig, H. A Boradiselenirane and a Boraditellurirane: Isolable Heavy Analogs of Dioxiranes and Dithiiranes. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2018\u003c/strong\u003e, \u003cem\u003e140\u003c/em\u003e, 11223\u0026minus;11226. (c) Chen, P.; Cui, C. Isolable Boron Persulfide: Activation of Elemental Sulfur with a 2‐Chloro‐Azaborolyl Anion. \u003cem\u003eChem. Eur. J. \u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, \u003cem\u003e22\u003c/em\u003e, 2902\u0026minus;2905. (d) Liu, S.; L\u0026eacute;gar\u0026eacute;, M.-A.; Hofmann, A.; Rempel, A.; Hagspiel, S.; Braunschweig, H. Synthesis of Unsymmetrical B\u003csub\u003e2\u003c/sub\u003eE\u003csub\u003e2\u003c/sub\u003e and B\u003csub\u003e2\u003c/sub\u003eE\u003csub\u003e3\u003c/sub\u003e Heterocycles by Borylene Insertion into Boradichalcogeniranes. \u003cem\u003eChem. Sci. \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e10\u003c/em\u003e, 4662\u0026minus;4666.\u003c/li\u003e\n\u003cli\u003eXiong, Y.; Yao, S.; M\u0026uuml;ller, R.; Kaupp, M.; Driess, M. From Silicon(II)-Based Dioxygen Activation to Adducts of Elusive Dioxasiliranes and Sila-ureas Stable at Room Temperature. \u003cem\u003eNat. Chem. \u003c/em\u003e\u003cstrong\u003e2010\u003c/strong\u003e, \u003cem\u003e2\u003c/em\u003e, 577\u0026minus;580.\u003c/li\u003e\n\u003cli\u003eNakamoto, M.; Akiba, K.-y. Stable Dioxaphosphirane Species:\u0026thinsp; Facile Formation by Reaction of 10-P-4\u003csup\u003e1\u003c/sup\u003e Hypervalent Phosphoranide with Atmospheric Oxygen. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e1999\u003c/strong\u003e, \u003cem\u003e121\u003c/em\u003e, 6958\u0026minus;6959.\u003c/li\u003e\n\u003cli\u003e(a) Dahcheh, F.; Martin, D.; Stephan, D. W.; Bertrand, G. Synthesis and Reactivity of a CAAC-Aminoborylene Adduct: A Hetero-Allene or an Organoboron Isoelectronic with Singlet Carbenes. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2014\u003c/strong\u003e, \u003cem\u003e53\u003c/em\u003e, 13159\u0026minus;13163. (b) Li, J.; Lu, Z.; Liu, L. L. A Free Phosphaborene Stable at Room Temperature. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2022\u003c/strong\u003e, \u003cem\u003e144\u003c/em\u003e, 23691\u0026minus;23697.\u003c/li\u003e\n\u003cli\u003e(a) Harvey, J. N. Understanding the Kinetics of Spin-Forbidden Chemical Reactions. \u003cem\u003ePhys. Chem. Chem. Phys. \u003c/em\u003e\u003cstrong\u003e2007\u003c/strong\u003e, \u003cem\u003e9\u003c/em\u003e, 331\u0026minus;343. (b) Tang, J.; Gao, X. J.; Tang, H.; Zeng, X. Dioxygen Activation with Stable N-heterocyclic Carbenes. \u003cem\u003eChem. Commun. \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e55\u003c/em\u003e, 1584\u0026minus;1587.\u003c/li\u003e\n\u003cli\u003eAnulewicz-Ostrowska, R.; Luliński, S.; Serwatowski, J.; Suwińska, K. Diverse Reactivity of Dialkylaluminum Dimesitylboryloxides [(\u0026mu;-Mes\u003csub\u003e2\u003c/sub\u003eBO)AlR\u003csub\u003e2\u003c/sub\u003e]\u003csub\u003e2\u003c/sub\u003e. Synthetic and Structural Study. \u003cem\u003eInorg. Chem. \u003c/em\u003e\u003cstrong\u003e2000\u003c/strong\u003e, \u003cem\u003e39\u003c/em\u003e, 5763\u0026minus;5767.\u003c/li\u003e\n\u003cli\u003e(a) Loh, Y. K.; Porteous, K.; Fuentes, M. \u0026Aacute;.; Do, D. C. H.; Hicks, J.; Aldridge, S. An Acid-Free Anionic Oxoborane Isoelectronic with Carbonyl: Facile Access and Transfer of a Terminal B=O Double Bond. \u003cem\u003eJ. Am. Chem. Soc. \u003c/em\u003e\u003cstrong\u003e2019\u003c/strong\u003e, \u003cem\u003e141\u003c/em\u003e, 8073\u0026minus;8077. (b) Millet, C. R. P.; Willcox, D. R.; Nichol, G. S.; Anst\u0026ouml;ter, C. S.; Ingleson, M. J. A Base-Free Two-Coordinate Oxoborane. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2025\u003c/strong\u003e, \u003cem\u003e64\u003c/em\u003e, e202419094. (c) Wang, H.; Zhang, J.; Yang, J.; Xie, Z. Synthesis, Structure, and Reactivity of Acid-Free Neutral Oxoborane. \u003cem\u003eAngew. Chem. Int. Ed. \u003c/em\u003e\u003cstrong\u003e2021\u003c/strong\u003e, \u003cem\u003e60\u003c/em\u003e, 19008\u0026minus;19012.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Schemes","content":"\u003cp\u003eSchemes 1 and 2 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Southern University of Science and Technology","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"boron, borylene, dioxaborirane, dioxygen","lastPublishedDoi":"10.21203/rs.3.rs-9677735/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9677735/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDioxaboriranes, the boron analogues of dioxiranes, are three-membered BO\u003csub\u003e2\u003c/sub\u003e main-group peroxides whose synthesis and characterization remain highly challenging. Herein, we report the straightforward synthesis and characterization of a crystalline dioxaborirane via direct borylene activation of triplet dioxygen. Mechanistic studies indicate a stepwise process involving end-on oxygen coordination, intersystem crossing, and subsequent ring closure. Single-crystal X-ray diffraction reveals a notably elongated O\u0026ndash;O bond, reflecting the combined effects of Pauli repulsion and ring strain. Furthermore, this dioxaborirane undergoes facile O\u0026ndash;O bond cleavage in the presence of Lewis acids such as AlMe\u003csub\u003e3\u003c/sub\u003e and AgOTf, yielding well-defined boron-oxygen species. This work establishes a rare example of an isolable dioxaborirane, elucidates the mechanism of borylene O\u003csub\u003e2\u003c/sub\u003e activation, and opens new avenues for the controlled exploitation of strained main-group peroxide motifs in synthesis and reactivity studies.\u003c/p\u003e","manuscriptTitle":"A Crystalline Dioxaborirane through Borylene Activation of Dioxygen","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-12 13:57:34","doi":"10.21203/rs.3.rs-9677735/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8de887a2-2160-4ee4-b4e8-e398b82300b1","owner":[],"postedDate":"May 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-12T13:57:34+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-12 13:57:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9677735","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9677735","identity":"rs-9677735","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}