1,2-C-H Activation of Benzene Promoted by (Arylimido)vanadium(V)-Alkylidene Complexes: Isolation of the Alkylidene, Benzyne Complexes

Reactions of the (arylimido)vanadium(V) dialkyl complex containing an imidazolin-2-iminato ligand, V(NAr)(CH2SiMe3)(2)(L) [2, Ar = 2,6-Me2C6H3; L = Im(DIPP) N = 1,3-(2',6'-diisopropylphenyl)imidazolin-2-iminato], with C6D6 or C6H6 took place affording the phenyl complex V(NAr)(CH2SiMe3)(C6H5)(L) (3) or V(NAr)[CH(D)SiMe3](C6D5)(L) (3-d(6)) by 1,2-C-H or C-D activation of benzene via a vanadium(V)-alkylidene intermediate. The reaction of 2 in n-hexane in the presence of PMe3 afforded the vanadium(V)alkylidene complex V(CHSiMe3)(NAr)(Im(DIPP)N)(PMe3) (4), and the structure of 4 has been determined by X-ray crystallography. The reaction of 3 or 3-d(6) with C6D6 or C6H6 took place to afford the diphenyl complex V(NAr) (C6H5)(2)(L) (5) or V(NAr)(C6D5)(2)(L) (5-d(10)). The same reaction in the presence of PMe3 afforded the proposed intermediate, the PMe3-trapped benzyne complex V(NAr)(eta(2)-C6D4)(L)(PMe3) (6), and the structure of 6 has been determined by X-ray diffraction analysis.