Dehydrogenation of hydrocarbons with metal-carbon multiple bonds and trapping of a titanium(II) intermediate

摘要

Reacting (PNP)TivCH~tBu(CH_2~tBu) with 2,2'-bipyridine (bipy) in cyclohexane or heptane results in dehydrogenation, cleanly producing cyclohexene and 1-heptene, respectively, and a TiII intermediate that is trapped by bipy to produce [(PNP)Ti~(III)(CH_2~tBu)(bipy?-)](1). This titanium(II) intermediate reduces the bipy ligand upon coordination to form a Ti~(III) center, where the unpaired electron is antiferromagnetically coupled to the electron of the reduced[bipy~(?-)] π-radical moiety, giving an overall diamagnetic species. Complex 1 has been characterized by NMR and UV-vis spectroscopies as well as single crystal X-ray diffraction studies.