Titanium(II) Porphyrin Complexes:  Versatile One- and Two-Electron Reducing Agents. Reduction of Organic Chlorides, Epoxides, and Sulfoxides

Treatment of the well-defined complexes (TTP)Ti(η 2 -EtC⋮CEt) or trans -(TTP)Ti(THF) 2 with vicinal dichloroalkanes or dichloroalkenes results in the production of alkenes or alkynes and 2 equiv of (TTP)TiCl. This net two-electron redox reaction arises from two formal one-electron reduction processes mediated by chlorine atom transfer. Oxygen atom transfer occurs when the Ti(II) porphyrins are treated with several different sulfoxides or epoxides, resulting in two-electron redox products, (TTP)Ti O, the sulfide or alkene, and EtC⋮CEt or THF. The electronic properties of the substituents on the sulfoxides or epoxides correlate with the yield and rate of the deoxygenation reactions.