Intermolecular Activation of C−X (X = H, O, F) Bonds by a Ti⋮C<i>^t</i>Bu Linkage

The transient titanium alkylidyne complex (PNP)Ti⋮CtBu (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-) can readily activate, in some cases regioselectively, the aromatic C−H bond of anisole and fluoro-substituted anisoles to generate titanium alkylidene complexes having a substituted aryl group. Intermolecular C−O bond activation occurs when perfluoroanisole reacts with (PNP)Ti⋮CtBu to afford the disubstituted alkylidene methoxide (PNP)TiC[tBu(C6F5)](OCH3). Likewise, intermediate (PNP)Ti⋮CtBu can also promote the intermolecular C−F activation of C6F6 and CF3C6F5 to generate disubstituted alkylidene fluorides (PNP)Ti[tBu(ArF)](F) (ArF = C6F5, C6F4CF3). In the case of Ar = C6F4CF3, the product resulting from para-aryl C−F activation was isolated. For the latter two C−F bond activation reactions, mixtures of alkylidene rotamers exist in solution. Complexes resulting from C−H, C−O, and C−F (including the rotamers for the latter reaction) activation have been characterized by single-crystal X-ray diffraction methods.