C(sp 3 )-H Oxidative Addition and Transfer Hydrogenation Chemistry of a Titanium(II) Synthon: Mimicry of Late-Metal Type Reactivity.

Two-electron reduction of the TiIV compound (ket guan)(ImDipp N)Ti(OTf)2 (3) gives the arene-masked complex (ket guan)(η6 -ImDipp N)Ti (1) in excellent yield. Upon standing in solution, 1 converts to a TiIV metallacycle (4) through dehydrogenation of a pendant isopropyl group. Spectroscopic evidence shows this transformation initially proceeds via the oxidative addition of a C(sp3 )-H bond and can be reversed upon exposure of 4 to H2 . Interestingly, treatment of 1 with cyclohexene gives cyclohexane and 4 via a titanium-mediated transfer hydrogenation reaction, a process that can be extended to catalytically hydrogenate other unsaturated hydrocarbons under mild conditions. These results, rare for the early-metals, suggest 1 possesses chemical characteristics reminiscent of noble, late-metals.