Tuning Catalytic Activity of Dimolybdenum Paddlewheel Complexes by Ligands:Mechanism Study on the Radical Addition Reaction of CCl4 to 1-Hexene

Tuning Catalytic Activity of Dimolybdenum Paddlewheel Complexes by Ligands:Mechanism Study on the Radical Addition Reaction of CCl4 to 1-Hexene | 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 Tuning Catalytic Activity of Dimolybdenum Paddlewheel Complexes by Ligands:Mechanism Study on the Radical Addition Reaction of CCl4 to 1-Hexene Ling Wang, Lixia Kang, Suhong Huo, Xueying Zhang, Xiaoyan Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-363576/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Apr, 2021 Read the published version in Structural Chemistry → Version 1 posted 3 You are reading this latest preprint version Abstract The detailed catalytic mechanism of a series of paddlewheel complexes [Mo 2 L 4 ] featuring Mo-Mo quadruply-bond on radical addition of CCl 4 to 1-hexene was studied using density functional theory. Different ligands of Mo-Mo bond are investigated to illustrate the ligand effect on the catalytic activity. The results show that the Mo-Mo quadruply-bond paddlewheel complexes have high catalytic activity on the title reaction. The whole reaction involves 4 steps. Firstly, the C-Cl bond of first CCl 4 is activated by [Mo 2 L 4 ] catalyst, [Mo 2 L 3 Cl] and CH 3 COOCCl 3 are obtained; Then the second CCl 4 adds to [Mo 2 L 3 Cl] to produce [Mo 2 L 3 Cl 2 ] and CCl 3 radical; CCl 3 radical interacts with 1-hexene to get an addition, the addition product which reacts with one Cl atom of [Mo 2 L 3 Cl 2 ] to get the last product n BuCHClCH 2 CCl 3 and regenerate [Mo 2 L 3 Cl]. The addition of the first CCl 4 to [Mo 2 L 4 ] catalyst is the rate-determining step of the whole reaction. Because this step is not in the catalytic cycle, the reaction would speed up after a certain period of time. The catalytic activity of dimolybdenum paddlewheel complex is depended on the natural population analysis (NPA) charge of Mo and the redox potential E(Mo 2 4+ /Mo 2 5+ ). The higher NPA of Mo atom and higher E(Mo 2 4+ /Mo 2 5+ ) of the catalyst, the higher catalytic activity it has. Our calculated results provide an explanation for experimental observations and useful insights for further development of bimetallic catalysts in radical addition reactions. General Biochemistry dimolybdnum paddlewheel complex metal-metal quadruply-bond radical addition catalytic activity ligand effect Figures Figure 1 Figure 2 Figure 3 1. Introduction Since the first dimolybdenum complex (molybdenum(II) acetate) containing Mo-Mo multiple bond was isolated and characterized [1], a large number of polymetal-metal bonding complexes have been synthesized [2-8]. In particular, the metal–metal bonded compounds with unique paddlewheel structures have played a major role in development of coordination chemistry [9] and continue to be of interest for their catalytic [10], photophysical [11], electronic [12], and structural properties[13] as well as reactivity [14, 15]. Among these paddlewheel compounds, dimolybdenum compounds (denotes as Mo 2 L 4 ) have attracted much more attention due to their unique configuration and catalytic applications [16-21]. The Mo 2 L 4 paddlewheel compounds possess a quadruple metal-metal bond (σ 2 π 4 δ 2 ) supported by four bridging ligands, such as carboxylates, amides, pyrrolidinates, etc [2, 22-24]. These compounds exhibits one-electron redox properties in radical transformation processes, which can result in reductively cleaving a carbon-halogen bond in organic halides to generate organic radicals [2, 4, 18, 24-26]. The study of K. Mashima et al showed that Mo 2 (OCOAr) 4 (Ar=2,4,6- i Pr 3 C 6 H 2 ) was used for a catalytic radical addition reaction of CCl 4 to 1-hexene in THF-d 8 at 80°C to give 1, 1, 1, 3-tetrachloroheptane regioselectively in 84% yield. They also found that the redox properties of [Mo 2 ] complexes are changed by replacing the ligands, the catalytic activity for the radical addition reaction strongly depended on the redox potential of the [Mo 2 ] complexes [4]. N. J. Patmore found that the electronic structure of Mo-Mo quadruple bonds can be tuned through O/S substitution of N by lowering the HOMO energy of Mo 2 and reducing the Mo 2 4+/5+ oxidation potential [27]. In 2017, Mashima K. et al synthesized a series of mixed ligated tris(amidinate) dimolybdenum complexes as catalysts for radical addition of CCl 4 to 1‑hexene [24]. Their experimental investigation showed that the nature of the L ligands was a crucial factor for initiating the catalytic reaction. Rational catalytic cycle of radical addition reaction catalyzed by [Mo 2 (DAniF) 3 (OCO(CH 3 ))] (DAniF = CH 3 NCHNCH 3 ) is proposed (Scheme 1). The catalytic activities of series of mixed-ligated dimolybdenum complexes are higher than those of homoleptic Mo 2 complexes [24]. In this work, the addition reaction between CCl 4 and 1-hexene catalysed by a series of quadruple-bonded dimolybdenum complexes are investigated based on density functional theory. The aims of this work are (1) to illustrate the addition reaction mechanism of CCl 4 and 1-hexene catalysed by the quadruple-bonded dimolybdenum complexes; (2) to determine how the ligand tuning the catalytic activity of Mo 2 L 4 and (3) to screen out the ligands of Mo 2 L 4 with high activity. We seek to provide theoretical prediction for the catalytic activity of quadruple-bonded dimolybdenum paddlewheel complexes on radical addition reaction and to inspire the future applications in organic syntheses. 2. Computational Details All of the calculations were performed at PBEPBE-D3 [28-29]/Def2-SVP[30, 31] level using Gaussian 09 package [32]. A functional, including dispersion correction [33, 34], has been proven that it can provide accurate energies for transition metals [35]. The vibrational frequency calculations were calculated at the same level to confirm the stable structure has no and the transition state has only one imaginary frequency. Intrinsic reaction coordinate (IRC) [36, 37] was calculated to confirm the linkage relationship between the transition states and stable points. In order to characterize the chemical bond changes in the reaction pathway, the Wiberg bond index and natural population charge were also obtained at the PBEPBE/Def2-SVP level using NBO 3.1 program [38]. 3. Results And Discussion 3.1 Catalytic Mechanism of Mo 2 (CH 3 NCHNCH 3 ) 3 (OCOCH 3 ) (denoted as CAT) on title reaction Based on the catalytic cycle for addition reaction of CCl 4 to 1-hexene catalysed by CAT (Scheme 1), the catalytic mechanism has been calculated and determined. This transformation involves 4 steps. Firstly, the C-Cl bond of first CCl 4 is activated by CAT, [Mo 2 L 3 Cl](L=CH 3 NCHNCH 3 ) and CH 3 COOCCl 3 are obtained; Then the second CCl 4 adds to Mo 2 L 3 Cl to produce [Mo 2 L 3 Cl 2 ] and CCl 3 radical; CCl 3 radical interacts with 1-hexene to carry out another addition reaction, and Cl atom migrates from [Mo 2 L 3 Cl 2 ] to get product 1,1,1,3-tetrachloroheptane n BuCHClCH 2 CCl 3 and [Mo 2 L 3 Cl] is regenerated. The optimized geometries of the catalyst, reactants, complexes (COM), transition states (TS), and products are shown in Fig. 1, with the main parameters labelled on the geometries. The optimized xyz coordinates for the stationary points are given in Table S1-S22 (Supporting Information). The potential energy surfaces of the C-Cl bond activation are shown in Fig. 2 and those of the addition reactions in Fig. 3. For convenience, the total energy of the reactants of each step is taken as the reference zero of energy. First C-Cl bond activation: At the beginning of the reaction between CAT and CCl 4 , the Cl of CCl 4 firstly interacts with one of the Mo atom of CAT to form COM1. In COM1, the two Mo atoms and two O atoms are in the same plane (D Mo-Mo-O-O =0°), the bond length of Mo-O bond near the CCl 4 is 2.137 Å. As the reaction proceeding, the Cl atom goes near to the Mo atom. At the same time, the O atom of OCOCH 3 ligand is pushed to leave away the Mo atom. In TS1, the distance between Mo and Cl decreases from 3.506 Å to 2.618 Å, the Mo-O bond length increases to 3.128 Å, which means that Mo-O bond is broken. After TS1, the C-Cl bond of CCl 4 elongates gradually and the OCOCH 3 ligand leaves away the Mo atom, the D Mo-Mo-O-O =-73.8° in COM2. Through TS2, the CCl 3 and OCOCH 3 leave away the [Mo 2 ] group and interact with each other to form CH 3 OOCCl 3 and [Mo 2 (CH 3 NCHNCH 3 ) 3 Cl] (PCl). In PCl, the Cl atom is above the Mo-Mo bond, and the two Mo-Cl bonds are just the equal. The potential energy surface of this step reaction is shown in Fig. 2(1). The energy barrier (ΔG # ) of TS1 is 20.8 kcal/mol and that of TS2 is 21.0 kcal/mol, the energy barriers are not high, thus, this step could happen at mild conditions. Our calculated ΔG # is slightly smaller than that determined by kinetic experimental results, 26.0kcal/mol at 303K [24]. The experimental value is larger because it is determined in the presence of excess CCl 4 and pyridine; the coordination of pyridine suppresses the reaction, which has been found in former studies [2, 8]. In this step, the changes of Mo-Mo bond are slight. In CAT, the bond length of Mo-Mo bond is 2.098 Å and the Wiberg bond order is 3.18. As the reaction proceeding, the Mo-Mo bond length increases a little. In PCl, the Wiberg bond order of Mo-Mo bond (3.23) is slightly larger than that in CAT. Second C-Cl bond activation: The second step also begins at the Cl atom of CCl 4 attacking the Mo atom of PCl to form the COM4. Then, this Cl atom links to Mo atom and pushes the Cl atom in PC1 to another Mo atom through TS3 to form [Mo 2 (CH 3 NCHNCH 3 ) 3 Cl 2 ] (PCl2) and CCl 3 radical. As shown in Figure 2(2), the ΔG # of TS3 is only 1.6 kcal/mol and the energy of TS3 is lower than the sum energy of separated reactants PCl and CCl 4 , meaning this step can occur easily. In PCl2, the Mo-Mo bond order decreases to 2.69. CCl 3 addition to 1-hexene: The dissociated ·CCl 3 radical attacks the C1 atom of 1-hexene with a energy barrier of 9.0 kcal/mol (Fig. 3). In this reaction process, the spin electron density migrates from the C atom of CCl 3 radical to the C1 atom of 1-hexene, COM7 forms. This step has been discussed in our former work [8]. Cl atom migration and [Mo 2 L 3 Cl] regeneration: The last step of the reaction is the C2 atom of COM7 interacts with one Cl atom of PCl2, the Cl atom migrates from Mo atom to C2 atom via TS5. After TS5, COM9 forms, then it separates to Product (Pro) 1, 1, 1, 3-tetrachloroheptane and PCl. The ΔG # of this step is 16.2 kcal/mol. In summary, the whole reaction pathway contains four steps. Among them, the first C-Cl bond activation process is the rate-determining step and it is not in the catalytic cycle. The catalytic cycle contains the second C-Cl bond activation, · CCl 3 radical addition to 1-hexene, Cl atom migration and [Mo 2 L 3 Cl] regeneration processes. The ΔG # of the first step are about 22.0 kcal/mol, those of other three steps are within 20.0 kcal/mol. Therefore, increasing the reaction temperature could accelerate the first C-Cl bond activation process, and the whole reaction would speed up after a certain period of time and not need the heating. 3.2 Influences of ligands on the catalytic activity Based on the mechanism study, the first step is the rate-determining step, and the experimental results show that the catalytic activity is correlated to the redox potential of Mo 2 4+ / Mo 2 5+ [4, 27].In order to screen out the high activity catalyst, the electronic structures of [Mo 2 ] complexes with different ligands are calculated. The relationship between the electronic structure and the ΔG # of the first step is found to determine how the ligand tuning the catalytic activity of Mo 2 L 4 . The following catalysts are considered (Scheme 2). The Gibbs energy barriers (ΔG 1 # ), redox potentials (E(Mo 2 4+ /Mo 2 5+ )) and natural population analysis charges of Mo atom of different catalysts are listed in Table 1. The redox potentials [39] are calculated as follow: Geometries were optimized in gas phase followed by single point energy calculations in solvent CHCl 3 . Solvation was modelled by the polarized continuum model (PCM). The Gibbs free energies of the redox reaction in CHCl 3 were calculated as follows: ΔG solv =ΔG solv (Mo 2 4+ )-ΔG solv (Mo 2 5+ ) (1) Then the calculated Gibbs free energies were converted to absolute electron redox potential according to Nernst equation: ΔG solv =-FE(Mo 2 4+ / Mo 2 5+ ) (2) where F is the Faraday constant, 96500 C∙mol -1 . Comparing the redox potential of Mo 2 (CH 3 NCHNCH 3 ) 4 with those of mixed-ligated [Mo 2 ] catalysts, it can be seen that the E(Mo 2 4+ /Mo 2 5+ ) of Mo 2 (CH 3 NCHNCH 3 ) 4 is the lowest. As one CH 3 NCHNCH 3 ligand is substituted by OCO(R) (R= CH 3 , 3-py, 4-py, ph, Furan), the redox potential of E(Mo 2 4+ /Mo 2 5+ ) increases distinctly. Moreover, the NPA charges of Mo atoms are also increased. The more positive charge of Mo atom will facilitate the attacking of Mo to Cl of CCl 4 with negative charge. Thus, the catalytic activities of mixed-ligated [Mo 2 ] catalysts are higher than those of homoleptic. The R in the ligands has little influence on the activity. In total, the catalytic activity is correlated to the redox potential of E(Mo 2 4+ /Mo 2 5+ ) and NPA charge of Mo. The higher E(Mo 2 4+ /Mo 2 5+ ) and NPA charge of the catalyst, the higher activity it has. 4. Conclusions The detailed catalytic mechanism of a series of paddlewheel complexes [Mo 2 L 4 ] featuring Mo-Mo quadruply-bond with different ligands on radical addition of CCl 4 to 1-hexene was investigated. The following conclusions can be drawn: The Mo-Mo quadruply-bond paddlewheel complexes are good catalysts on the radical addition reaction of CCl 4 to 1-hexene. The whole reaction involves 4 steps. The addition of the first CCl 4 is the rate-determining step of the whole reaction; the reaction would speed up after a certain period of time. The catalytic activity of dimolybdenum paddlewheel complex is depended on the natural population analysis (NPA) charge of Mo and the redox potential E(Mo 4+ /Mo 5+ ). The higher E(Mo 2 4+ /Mo 2 5+ ) and NPA charge of the catalyst, the higher activity it has. Declarations ASSOCIATED CONTENT Supporting Information. The following files are available free of charge. Calculated Gibbs free energy and XYZ coordinates of the stable points. Declarations Funding Sources This work was supported by National Natural Science Foundation of China (Contract Nos. 21973027, 21973025), Natural Science Foundation of Hebei Province (Contract No. B2020205002, B2019205061, B2018205198). Conflict of interest The authors declare that they have no conflict of interest. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. 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Δ G 1 # E (Mo 4+ /Mo 5+ ) charge Mo 2 (CH 3 NCHNCH 3 ) 4 25.4 337.0 0.495 Mo 2 (CH 3 NCHNCH 3 ) 3 (OCO(CH 3 )) 21.0 425.4 0.587 Mo 2 (CH 3 NCHNCH 3 ) 3 (OCO(3-py)) 20.2 1603.6 0.600 Mo 2 (CH 3 NCHNCH 3 ) 3 (OCO(4-py)) 19.2 1754.2 0.605 Mo 2 (CH 3 NCHNCH 3 ) 3 (OCO(Ph)) 20.8 1153.9 0.598 Mo 2 (CH 3 NCHNCH 3 ) 3 (OCO(2-Furan)) 21.7 907.3 0.596 Ph=C 6 H 5 , Py= C 5 H 5 N, Furan =C 4 H 4 O. Supplementary Files supportinginformation.docx Cite Share Download PDF Status: Published Journal Publication published 26 Apr, 2021 Read the published version in Structural Chemistry → Version 1 posted Reviews received at journal 30 Mar, 2021 First submitted to journal 24 Mar, 2021 Editor assigned by journal 24 Mar, 2021 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. 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2","display":"","copyAsset":false,"role":"figure","size":60045,"visible":true,"origin":"","legend":"Potential energy surfaces of the C-Cl bond activation","description":"","filename":"f2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-363576/v1/edd7699e9f0b8ebb367b6cf9.jpg"},{"id":7622387,"identity":"7d057cf1-dca8-464e-acff-d158dae19ff1","added_by":"auto","created_at":"2021-04-02 21:23:08","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":50261,"visible":true,"origin":"","legend":"Potential energy surfaces of the addition reactions","description":"","filename":"f3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-363576/v1/08e71da36f912e4f01a4b08a.jpg"},{"id":13683704,"identity":"f4435c4a-e1be-49de-b447-54ae77311b09","added_by":"auto","created_at":"2021-09-17 12:03:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":406045,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-363576/v1/9e8bb459-ab08-4c41-b2d5-a143d4fc0c8d.pdf"},{"id":7622388,"identity":"802e1321-9d40-4f18-bbaf-a6c673113e5d","added_by":"auto","created_at":"2021-04-02 21:23:09","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":92115,"visible":true,"origin":"","legend":"","description":"","filename":"supportinginformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-363576/v1/4dfbf4df7bf17fc9119daf14.docx"}],"financialInterests":"","formattedTitle":"Tuning Catalytic Activity of Dimolybdenum Paddlewheel Complexes by Ligands:Mechanism Study on the Radical Addition Reaction of CCl4 to 1-Hexene","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSince the first dimolybdenum complex (molybdenum(II) acetate) containing Mo-Mo multiple bond was isolated and characterized [1], a large number of polymetal-metal bonding complexes have been synthesized [2-8]. In particular, the metal\u0026ndash;metal bonded compounds with unique paddlewheel structures have played a major role in development of coordination chemistry [9] and continue to be of interest for their catalytic [10], photophysical [11], electronic [12], and structural properties[13] as well as reactivity [14, 15]. Among these paddlewheel compounds, dimolybdenum compounds (denotes as Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e) have attracted much more attention due to their unique configuration and catalytic applications [16-21]. The Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e paddlewheel compounds possess a quadruple metal-metal bond (\u0026sigma;\u003csup\u003e2\u003c/sup\u003e\u0026pi;\u003csup\u003e4\u003c/sup\u003e\u0026delta;\u003csup\u003e2\u003c/sup\u003e) supported by four bridging ligands, such as carboxylates, amides, pyrrolidinates, etc [2, 22-24]. These compounds exhibits one-electron redox properties in radical transformation processes, which can result in reductively cleaving a carbon-halogen bond in organic halides to generate organic radicals [2, 4, 18, 24-26].\u003c/p\u003e\n\u003cp\u003eThe study of K. Mashima et al showed that Mo\u003csub\u003e2\u003c/sub\u003e(OCOAr)\u003csub\u003e4\u003c/sub\u003e (Ar=2,4,6-\u003csup\u003ei\u003c/sup\u003ePr\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003e) was used for a catalytic radical addition reaction of CCl\u003csub\u003e4\u003c/sub\u003e to 1-hexene in THF-d\u003csub\u003e8\u003c/sub\u003e at 80\u0026deg;C to give 1, 1, 1, 3-tetrachloroheptane regioselectively in 84% yield. They also found that the redox properties of [Mo\u003csub\u003e2\u003c/sub\u003e] complexes are changed by replacing the ligands, the catalytic activity for the radical addition reaction strongly depended on the redox potential of the [Mo\u003csub\u003e2\u003c/sub\u003e] complexes [4]. N. J. Patmore found that the electronic structure of Mo-Mo quadruple bonds can be tuned through O/S substitution of N by lowering the HOMO energy of Mo\u003csub\u003e2\u003c/sub\u003e and reducing the Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+/5+\u003c/sup\u003e oxidation potential [27].\u003c/p\u003e\n\u003cp\u003eIn 2017, Mashima K. et al synthesized a series of mixed ligated tris(amidinate) dimolybdenum complexes as catalysts for radical addition of CCl\u003csub\u003e4\u003c/sub\u003e to 1‑hexene [24]. Their experimental investigation showed that the nature of the L ligands was a crucial factor for initiating the catalytic reaction. Rational catalytic cycle of radical addition reaction catalyzed by [Mo\u003csub\u003e2\u003c/sub\u003e(DAniF)\u003csub\u003e3\u003c/sub\u003e(OCO(CH\u003csub\u003e3\u003c/sub\u003e))] (DAniF = CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e) is proposed (Scheme 1). The catalytic activities of series of mixed-ligated dimolybdenum complexes are higher than those of homoleptic Mo\u003csub\u003e2\u003c/sub\u003e complexes [24].\u003c/p\u003e\n\u003cp\u003eIn this work, the addition reaction between CCl\u003csub\u003e4\u003c/sub\u003e and 1-hexene catalysed by a series of quadruple-bonded dimolybdenum complexes are investigated based on density functional theory. The aims of this work are (1) to illustrate the addition reaction mechanism of CCl\u003csub\u003e4\u003c/sub\u003e and 1-hexene catalysed by the quadruple-bonded dimolybdenum complexes; (2) to determine how the ligand tuning the catalytic activity of Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e and (3) to screen out the ligands of Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e with high activity. We seek to provide theoretical prediction for the catalytic activity of quadruple-bonded dimolybdenum paddlewheel complexes on radical addition reaction and to inspire the future applications in organic syntheses.\u003c/p\u003e"},{"header":"2. Computational Details","content":"\u003cp\u003eAll of the calculations were performed at PBEPBE-D3 [28-29]/Def2-SVP[30, 31] level using Gaussian 09 package [32]. A functional, including dispersion correction [33, 34], has been proven that it can provide accurate energies for transition metals [35]. The vibrational frequency calculations were calculated at the same level to confirm the stable structure has no and the transition state has only one imaginary frequency. Intrinsic reaction coordinate (IRC) [36, 37] was calculated to confirm the linkage relationship between the transition states and stable points. In order to characterize the chemical bond changes in the reaction pathway, the Wiberg bond index and natural population charge were also obtained at the PBEPBE/Def2-SVP level using NBO 3.1 program [38].\u003c/p\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003e\u003cstrong\u003e3.1 Catalytic Mechanism of Mo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OCOCH\u003csub\u003e3\u003c/sub\u003e) (denoted as CAT) on title reaction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBased on the catalytic cycle for addition reaction of CCl\u003csub\u003e4\u003c/sub\u003e to 1-hexene catalysed by CAT (Scheme 1), the catalytic mechanism has been calculated and determined. This transformation involves 4 steps. Firstly, the C-Cl bond of first CCl\u003csub\u003e4\u003c/sub\u003e is activated by CAT, [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl](L=CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e) and CH\u003csub\u003e3\u003c/sub\u003eCOOCCl\u003csub\u003e3\u003c/sub\u003e are obtained; Then the second CCl\u003csub\u003e4\u003c/sub\u003e adds to Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl to produce [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e] and CCl\u003csub\u003e3\u003c/sub\u003e radical; CCl\u003csub\u003e3\u003c/sub\u003e radical interacts with 1-hexene to carry out another addition reaction, and Cl atom migrates from [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e] to get product 1,1,1,3-tetrachloroheptane \u003csup\u003en\u003c/sup\u003eBuCHClCH\u003csub\u003e2\u003c/sub\u003eCCl\u003csub\u003e3 \u003c/sub\u003eand [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl] is regenerated. The optimized geometries of the catalyst, reactants, complexes (COM), transition states (TS), and products are shown in Fig. 1, with the main parameters labelled on the geometries. The optimized xyz coordinates for the stationary points are given in Table S1-S22 (Supporting Information). The potential energy surfaces of the C-Cl bond activation are shown in Fig. 2 and those of the addition reactions in Fig. 3. For convenience, the total energy of the reactants of each step is taken as the reference zero of energy.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFirst C-Cl bond activation:\u003c/em\u003e At the beginning of the reaction between CAT and CCl\u003csub\u003e4\u003c/sub\u003e, the Cl of CCl\u003csub\u003e4\u003c/sub\u003e firstly interacts with one of the Mo atom of CAT to form COM1. In COM1, the two Mo atoms and two O atoms are in the same plane (D\u003csub\u003eMo-Mo-O-O\u003c/sub\u003e=0\u0026deg;), the bond length of Mo-O bond near the CCl\u003csub\u003e4\u003c/sub\u003e is 2.137 \u0026Aring;. As the reaction proceeding, the Cl atom goes near to the Mo atom. At the same time, the O atom of OCOCH\u003csub\u003e3\u003c/sub\u003e ligand is pushed to leave away the Mo atom. In TS1, the distance between Mo and Cl decreases from 3.506 \u0026Aring; to 2.618 \u0026Aring;, the Mo-O bond length increases to 3.128 \u0026Aring;, which means that Mo-O bond is broken. After TS1, the C-Cl bond of CCl\u003csub\u003e4\u003c/sub\u003e elongates gradually and the OCOCH\u003csub\u003e3\u003c/sub\u003e ligand leaves away the Mo atom, the D\u003csub\u003eMo-Mo-O-O\u003c/sub\u003e=-73.8\u0026deg; in COM2. Through TS2, the CCl\u003csub\u003e3\u003c/sub\u003e and OCOCH\u003csub\u003e3\u003c/sub\u003e leave away the [Mo\u003csub\u003e2\u003c/sub\u003e] group and interact with each other to form CH\u003csub\u003e3\u003c/sub\u003eOOCCl\u003csub\u003e3\u003c/sub\u003e and [Mo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eCl] (PCl). In PCl, the Cl atom is above the Mo-Mo bond, and the two Mo-Cl bonds are just the equal.\u003c/p\u003e\n\u003cp\u003eThe potential energy surface of this step reaction is shown in Fig. 2(1). The energy barrier (\u0026Delta;G\u003csup\u003e#\u003c/sup\u003e) of TS1 is 20.8 kcal/mol and that of TS2 is 21.0 kcal/mol, the energy barriers are not high, thus, this step could happen at mild conditions. Our calculated \u0026Delta;G\u003csup\u003e#\u003c/sup\u003e is slightly smaller than that determined by kinetic experimental results, 26.0kcal/mol at 303K [24]. The experimental value is larger because it is determined in the presence of excess CCl\u003csub\u003e4\u003c/sub\u003e and pyridine; the coordination of pyridine suppresses the reaction, which has been found in former studies [2, 8]. In this step, the changes of Mo-Mo bond are slight. In CAT, the bond length of Mo-Mo bond is 2.098 \u0026Aring; and the Wiberg bond order is 3.18. As the reaction proceeding, the Mo-Mo bond length increases a little. In PCl, the Wiberg bond order of Mo-Mo bond (3.23) is slightly larger than that in CAT.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSecond C-Cl bond activation: \u003c/em\u003eThe second step also begins at the Cl atom of CCl\u003csub\u003e4\u003c/sub\u003e attacking the Mo atom of PCl to form the COM4. Then, this Cl atom links to Mo atom and pushes the Cl atom in PC1 to another Mo atom through TS3 to form [Mo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e] (PCl2) and CCl\u003csub\u003e3\u003c/sub\u003e radical. As shown in Figure 2(2), the \u0026Delta;G\u003csup\u003e#\u003c/sup\u003e of TS3 is only 1.6 kcal/mol and the energy of TS3 is lower than the sum energy of separated reactants PCl and CCl\u003csub\u003e4\u003c/sub\u003e, meaning this step can occur easily. In PCl2, the Mo-Mo bond order decreases to 2.69.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCCl\u003csub\u003e3\u003c/sub\u003e addition to 1-hexene: \u003c/em\u003eThe dissociated \u0026middot;CCl\u003csub\u003e3\u003c/sub\u003e radical attacks the C1 atom of 1-hexene with a energy barrier of 9.0 kcal/mol (Fig. 3). In this reaction process, the spin electron density migrates from the C atom of CCl\u003csub\u003e3\u003c/sub\u003e radical to the C1 atom of 1-hexene, COM7 forms. This step has been discussed in our former work [8].\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCl atom migration and [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl] regeneration:\u003c/em\u003e The last step of the reaction is the C2 atom of COM7 interacts with one Cl atom of PCl2, the Cl atom migrates from Mo atom to C2 atom \u003cem\u003evia\u003c/em\u003e TS5. After TS5, COM9 forms, then it separates to Product (Pro) 1, 1, 1, 3-tetrachloroheptane and PCl. The \u0026Delta;G\u003csup\u003e#\u003c/sup\u003e of this step is 16.2 kcal/mol.\u003c/p\u003e\n\u003cp\u003eIn summary, the whole reaction pathway contains four steps. Among them, the first C-Cl bond activation process is the rate-determining step and it is not in the catalytic cycle. The catalytic cycle contains the second C-Cl bond activation, \u003cem\u003e\u003csub\u003e\u0026middot;\u003c/sub\u003e\u003c/em\u003eCCl\u003csub\u003e3\u003c/sub\u003e radical addition to 1-hexene, Cl atom migration and [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl] regeneration processes. The \u0026Delta;G\u003csup\u003e#\u003c/sup\u003e of the first step are about 22.0 kcal/mol, those of other three steps are within 20.0 kcal/mol. Therefore, increasing the reaction temperature could accelerate the first C-Cl bond activation process, and the whole reaction would speed up after a certain period of time and not need the heating.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Influences of ligands on the catalytic activity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBased on the mechanism study, the first step is the rate-determining step, and the experimental results show that the catalytic activity is correlated to the redox potential of Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/ Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e[4, 27].In order to screen out the high activity catalyst, the electronic structures of [Mo\u003csub\u003e2\u003c/sub\u003e] complexes with different ligands are calculated. The relationship between the electronic structure and the \u0026Delta;G\u003csup\u003e#\u003c/sup\u003e of the first step is found to determine how the ligand tuning the catalytic activity of Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e. The following catalysts are considered (Scheme 2).\u003c/p\u003e\n\u003cp\u003eThe Gibbs energy barriers (\u0026Delta;G\u003csub\u003e1\u003c/sub\u003e\u003csup\u003e#\u003c/sup\u003e), redox potentials (E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e)) and natural population analysis charges of Mo atom of different catalysts are listed in Table 1. The redox potentials [39] are calculated as follow: Geometries were optimized in gas phase followed by single point energy calculations in solvent CHCl\u003csub\u003e3\u003c/sub\u003e. Solvation was modelled by the polarized continuum model (PCM). The Gibbs free energies of the redox reaction in CHCl\u003csub\u003e3\u003c/sub\u003e were calculated as follows:\u003c/p\u003e\n\u003cp\u003e\u0026Delta;G\u003csub\u003esolv\u003c/sub\u003e=\u0026Delta;G\u003csub\u003esolv\u003c/sub\u003e(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e)-\u0026Delta;G\u003csub\u003esolv\u003c/sub\u003e(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) (1)\u003c/p\u003e\n\u003cp\u003eThen the calculated Gibbs free energies were converted to absolute electron redox potential according to Nernst equation:\u003c/p\u003e\n\u003cp\u003e\u0026Delta;G\u003csub\u003esolv\u003c/sub\u003e=-FE(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/ Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) (2)\u003c/p\u003e\n\u003cp\u003ewhere F is the Faraday constant, 96500 C∙mol\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eComparing the redox potential of Mo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e4\u003c/sub\u003e with those of mixed-ligated [Mo\u003csub\u003e2\u003c/sub\u003e] catalysts, it can be seen that the E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) of Mo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e4\u003c/sub\u003e is the lowest. As one CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e ligand is substituted by OCO(R) (R= CH\u003csub\u003e3\u003c/sub\u003e, 3-py, 4-py, ph, Furan), the redox potential of E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) increases distinctly. Moreover, the NPA charges of Mo atoms are also increased. The more positive charge of Mo atom will facilitate the attacking of Mo to Cl of CCl\u003csub\u003e4\u003c/sub\u003e with negative charge. Thus, the catalytic activities of mixed-ligated [Mo\u003csub\u003e2\u003c/sub\u003e] catalysts are higher than those of homoleptic. The R in the ligands has little influence on the activity.\u003c/p\u003e\n\u003cp\u003eIn total, the catalytic activity is correlated to the redox potential of E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) and NPA charge of Mo. The higher E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) and NPA charge of the catalyst, the higher activity it has.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe detailed catalytic mechanism of a series of paddlewheel complexes [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e] featuring Mo-Mo quadruply-bond with different ligands on radical addition of CCl\u003csub\u003e4\u003c/sub\u003e to 1-hexene was investigated. The following conclusions can be drawn:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003eThe Mo-Mo quadruply-bond paddlewheel complexes are good catalysts on the radical addition reaction of CCl\u003csub\u003e4\u003c/sub\u003e to 1-hexene.\u003c/li\u003e\n\u003cli\u003eThe whole reaction involves 4 steps. The addition of the first CCl\u003csub\u003e4\u003c/sub\u003e is the rate-determining step of the whole reaction; the reaction would speed up after a certain period of time.\u003c/li\u003e\n\u003cli\u003eThe catalytic activity of dimolybdenum paddlewheel complex is depended on the natural population analysis (NPA) charge of Mo and the redox potential E(Mo\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csup\u003e5+\u003c/sup\u003e). The higher E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) and NPA charge of the catalyst, the higher activity it has.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Declarations","content":"\u003cp\u003eASSOCIATED CONTENT\u003c/p\u003e\n\u003cp\u003eSupporting Information. The following files are available free of charge. Calculated Gibbs free energy and XYZ coordinates of the stable points.\u003c/p\u003e\n\u003cp\u003eDeclarations\u003c/p\u003e\n\u003cp\u003eFunding Sources\u003c/p\u003e\n\u003cp\u003eThis work was supported by National Natural Science Foundation of China (Contract Nos. 21973027, 21973025), Natural Science Foundation of Hebei Province (Contract No. B2020205002, B2019205061, B2018205198).\u003c/p\u003e\n\u003cp\u003eConflict of interest\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eThe manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003eNotes\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003c/p\u003e"},{"header":"References","content":"\u003cp\u003e1.Lawton D, Mason R(1965) J Am Chem Soc 87: 921-922.\u003c/p\u003e\n\u003cp\u003e2.Cotton FA, Donahue JP, Gruhn NE, Lichtenberger DL, Murillo CA, Timmons DJ, VanDorn O, Villagr\u0026aacute;n D, Wang X(2006) Inorg Chem 45: 201-213.\u003c/p\u003e\n\u003cp\u003e3.Cotton FA, Murillo CA, Wang X, Wilkinson CC(2006) Inorg Chem 45:5493-5500.\u003c/p\u003e\n\u003cp\u003e4.Tsurugi H, Yamada K, Majumdar M, Sugin Y, Hayakawa A, Mashima K(2011) Dalton Trans 40: 9358-9361.\u003c/p\u003e\n\u003cp\u003e5.Brogden DW, Berry JF(2015) Inorg Chem 54: 7660-7665.\u003c/p\u003e\n\u003cp\u003e6.Noor A, Wagner FR, Kempe R(2008) Angew Chem 120: 7356-7359.\u003c/p\u003e\n\u003cp\u003e7.Huang YL, Lu DY, Yu HC, Yu JSK, Hsu CW, Kuo TS, Lee GH, Wang Y, Yi-Chou Tsai,YC(2012) Angew Chem 124: 901-7905.\u003c/p\u003e\n\u003cp\u003e8.Kang LX, Huo SH, Meng LP, Li XY(2020) Appl Organomet Chem 34:e5726.\u003c/p\u003e\n\u003cp\u003e9.Cotton FA, Murillo CA, Walton RA, Walton RA(2005) Springer Science and Business Media, Springer Science and Business Media, Inc.\u003c/p\u003e\n\u003cp\u003e10.Doyle MP, Duffy R, Ratnikov M, Zhou L (2010) Chem Rev 110:704-724.\u003c/p\u003e\n\u003cp\u003e11.Chisholm MH, Lear BJ(2011) Chem Soc Rev 40: 5254.\u003c/p\u003e\n\u003cp\u003e12.Berry J(2010) Metal-Metal Bonding,\u0026nbsp;Parkin, G., Springer, pp. 1-28.\u003c/p\u003e\n\u003cp\u003e13.Filatov AS, Petrukhina MA(2010) Coord Chem Rev 254:2234-2246.\u003c/p\u003e\n\u003cp\u003e14.Timmer GH, Berry JF(2012) Chem Sci 3: 3038.\u003c/p\u003e\n\u003cp\u003e15.Hansen J, Davies HML(2008) Coord Chem Rev 252:545-555.\u003c/p\u003e\n\u003cp\u003e16.Yamashita Y, Salter MM, Aoyama K, Kobayashi S(2006) Angew Chem Int Ed 45:3816-3819.\u003c/p\u003e\n\u003cp\u003e17.Cotton FA, Feng X(1997) J Am Chem Soc 119: 7514-7520.\u003c/p\u003e\n\u003cp\u003e18.Tsurugi H, Hayakawa A, Kando S, Sugino Y, Mashima K(2015) Chem Sci 6:3434-3439.\u003c/p\u003e\n\u003cp\u003e19.Kn\u0026ouml;fel ND, Schweigert C, Feuerstein TJ, Schoo C, Reinfandt N, Unterreiner AN, Roesky PW(2018) Inorg Chem 57: 9364-9375.\u003c/p\u003e\n\u003cp\u003e20.Carrasco M, Curado N, \u0026Aacute;lvarez E, Maya C, Peloso R, Poveda, ML, Rodr\u0026iacute;guez A, Ruiz E, \u0026Aacute;lvarez S, Carmona E(2014) Chem Eur J 20: 6092 \u0026ndash; 6102.\u003c/p\u003e\n\u003cp\u003e21.Chisholm MH(2013) Coord Chem Rev 257:1576-1583.\u003c/p\u003e\n\u003cp\u003e22.Cotton FA, Daniels LM, Hillard EA, Murillo CA(2002) Inorg Chem 41:1639-1644.\u003c/p\u003e\n\u003cp\u003e23.Cotton FA(1983) J Chem Educ 60: 713.\u003c/p\u003e\n\u003cp\u003e24.Rej S, Majumdar M, Kando S, Sugino Y, Tsurugi H, Mashima K(2016) Inorg Chem 56: 634-644.\u003c/p\u003e\n\u003cp\u003e25.Rej S, Tsurugi H, Mashima K(2018) Coord Chem Rev 355:223-239.\u003c/p\u003e\n\u003cp\u003e26.Cotton FA, Daniels LM, Murillo CA, Timmons DJ, Wilkinson CC(2002) J Am Chem Soc 124:9249-9256.\u003c/p\u003e\n\u003cp\u003e27.Hicks J, Ring SP, Patmore NJ(2012) Dalton Trans.41:6641.\u003c/p\u003e\n\u003cp\u003e28.Perdew JP, Burke K, Ernzerhof M(1996) Phys Rev Lett 77:3865-3868.\u003c/p\u003e\n\u003cp\u003e29.Perdew JP, Burke K, Ernzerhof M(1997) Phys Rev Lett 78:1396-1396.\u003c/p\u003e\n\u003cp\u003e30.Weigend F, Ahlrichs R(2005) Phys Chem Chem Phys 7:3297-3305.\u003c/p\u003e\n\u003cp\u003e31.Weigend F (2005) Phys Chem Chem Phys 8: 1057-1065.\u003c/p\u003e\n\u003cp\u003e32. 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style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style='font-size: 13px; line-height: 150%; font-family: \"Times New Roman\", serif; color: rgb(0, 0, 0);'\u003eTable 1 Gibbs energy barrier (\u0026Delta;\u003cem\u003eG\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u003csup\u003e#\u003c/sup\u003e, in kcal/mol), redox potential (\u003cem\u003eE\u003c/em\u003e(Mo\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csup\u003e5+\u003c/sup\u003e) in mV) and natural population analysis(NPA) charge of Mo in different catalysts\u003c/span\u003e\u003c/p\u003e\n\u003ctable style=\"width:100.0%;border-collapse:collapse;border:none;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:50.36%;border-top:solid windowtext 1.0pt;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003eMo\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eCat.\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:13.66%;border-top:solid windowtext 1.0pt;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e\u0026Delta;\u003cem\u003eG\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e\u003csup\u003e#\u003c/sup\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:20.42%;border-top:solid windowtext 1.0pt;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cem\u003e\u003cspan style='font-size:13px;line-height: 150%;font-family:\"Times New Roman\",serif;'\u003eE\u003c/span\u003e\u003c/em\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e(Mo\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csup\u003e5+\u003c/sup\u003e)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:15.54%;border-top:solid windowtext 1.0pt;border-left:none;border-bottom:solid windowtext 1.0pt;border-right:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003echarge\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:50.36%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003eMo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e4\u003c/sub\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:13.66%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e25.4\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:20.42%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e337.0\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:15.54%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e0.495\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:50.36%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003eMo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OCO(CH\u003csub\u003e3\u003c/sub\u003e))\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:13.66%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e21.0\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:20.42%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e425.4\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:15.54%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e0.587\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width:50.36%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003eMo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OCO(3-py))\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:13.66%;border:none;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan 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style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003eMo\u003csub\u003e2\u003c/sub\u003e(CH\u003csub\u003e3\u003c/sub\u003eNCHNCH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OCO(2-Furan))\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:13.66%;border:none;border-bottom:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;\"\u003e\n \u003cp style='margin:0in;text-align:center;font-size:14px;font-family:\"Calibri\",sans-serif;line-height:150%;'\u003e\u003cspan style=\"color: rgb(0, 0, 0);\"\u003e\u003cspan style='font-size:13px;line-height:150%;font-family:\"Times New Roman\",serif;'\u003e21.7\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width:20.42%;border:none;border-bottom:solid windowtext 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Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"dimolybdnum paddlewheel complex, metal-metal quadruply-bond, radical addition, catalytic activity, ligand effect","lastPublishedDoi":"10.21203/rs.3.rs-363576/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-363576/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe detailed catalytic mechanism of a series of paddlewheel complexes [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e] featuring Mo-Mo quadruply-bond on radical addition of CCl\u003csub\u003e4\u003c/sub\u003e to 1-hexene was studied using density functional theory. Different ligands of Mo-Mo bond are investigated to illustrate the ligand effect on the catalytic activity. The results show that the Mo-Mo quadruply-bond paddlewheel complexes have high catalytic activity on the title reaction. The whole reaction involves 4 steps. Firstly, the C-Cl bond of first CCl\u003csub\u003e4\u003c/sub\u003e is activated by [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e] catalyst, [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl] and CH\u003csub\u003e3\u003c/sub\u003eCOOCCl\u003csub\u003e3\u003c/sub\u003e are obtained; Then the second CCl\u003csub\u003e4\u003c/sub\u003e adds to [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl] to produce [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e] and CCl\u003csub\u003e3\u003c/sub\u003e radical; CCl\u003csub\u003e3\u003c/sub\u003e radical interacts with 1-hexene to get an addition, the addition product which reacts with one Cl atom of [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e] to get the last product \u003csup\u003en\u003c/sup\u003eBuCHClCH\u003csub\u003e2\u003c/sub\u003eCCl\u003csub\u003e3\u003c/sub\u003e and regenerate [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e3\u003c/sub\u003eCl]. The addition of the first CCl\u003csub\u003e4\u003c/sub\u003e to [Mo\u003csub\u003e2\u003c/sub\u003eL\u003csub\u003e4\u003c/sub\u003e] catalyst is the rate-determining step of the whole reaction. Because this step is not in the catalytic cycle, the reaction would speed up after a certain period of time. The catalytic activity of dimolybdenum paddlewheel complex is depended on the natural population analysis (NPA) charge of Mo and the redox potential E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e). The higher NPA of Mo atom and higher E(Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e4+\u003c/sup\u003e/Mo\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5+\u003c/sup\u003e) of the catalyst, the higher catalytic activity it has. Our calculated results provide an explanation for experimental observations and useful insights for further development of bimetallic catalysts in radical addition reactions.\u003c/p\u003e","manuscriptTitle":"Tuning Catalytic Activity of Dimolybdenum Paddlewheel Complexes by Ligands:Mechanism Study on the Radical Addition Reaction of CCl4 to 1-Hexene","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-04-02 21:23:07","doi":"10.21203/rs.3.rs-363576/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2021-03-31T00:00:00+00:00","index":0,"fulltext":""},{"type":"submitted","content":"Structural Chemistry","date":"2021-03-25T03:32:28+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2021-03-25T00:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"baff052e-06df-4f24-8de6-488f17934c4f","owner":[],"postedDate":"April 2nd, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":3388032,"name":"General Biochemistry"}],"tags":[],"updatedAt":"2021-08-18T19:48:38+00:00","versionOfRecord":{"articleIdentity":"rs-363576","link":"https://doi.org/10.1007/s11224-021-01790-2","journal":{"identity":"structural-chemistry","isVorOnly":false,"title":"Structural Chemistry"},"publishedOn":"2021-04-26 19:07:11","publishedOnDateReadable":"April 26th, 2021"},"versionCreatedAt":"2021-04-02 21:23:07","video":"","vorDoi":"10.1007/s11224-021-01790-2","vorDoiUrl":"https://doi.org/10.1007/s11224-021-01790-2","workflowStages":[]},"version":"v1","identity":"rs-363576","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-363576","identity":"rs-363576","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}