Oxidatively Induced α-Hydrogen Abstraction. A Mild Protocol to Generate Terminal Titanium Alkylidenes Containing a β-Hydrogen

One-electron oxidation of the Ti(III) bis-isobutyl complexes (nacnac)Ti(CH₂ⁱPr)₂ (1) (nacnac^- = [ArNC(^tBu)]₂CH, Ar = 2,6-ⁱPr₂C₆H₃) and (PNP)Ti(CH₂ⁱPr)₂ (4) (PNP^- = N[2-P(CHMe₂)₂-4-methylphenyl]₂) with AgOTf promotes exclusive α-hydrogen abstraction to provide the first structurally characterized examples of terminal group 4 alkylidenes bearing a β-hydrogen, namely, (nacnac)TiCHⁱPr(OTf) (2) and (PNP)TiCHⁱPr(OTf) (5). These complexes have been prepared and characterized by means of multinuclear NMR spectroscopy as well as single-crystal X-ray diffraction analysis. In the case of the nacnac framework, the reactive TiCHⁱPr motif can readily engage in an intramolecular Wittig-like rearrangement. However, the isobutylidene motif can be stabilized when supported by a more robust ancillary ligand such as PNP, which is demonstrated by the thermal resistance of 5 and the preparation of a rare example of a stable alkylidene methyl complex (PNP)TiCHⁱPr(Me) (6).