Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

The masked Ti(II) synthon ( Ket guan)( η 6 -Im Dipp N)Ti ( 1 ) oxidatively adds across thiophene to give ring-opened ( Ket guan)(Im Dipp N)Ti[ κ 2 - S (CH) 3 C H] ( 2 ). Complex 2 is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate 1 – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from 2 . Finally, pressurizing solutions of 2 with H 2 (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide ( Ket guan)(Im Dipp N)Ti(S) ( 3 ) and butane.