Formation of Derivative Carbyne Complexes from Tp‘(CO)₂M⋮CCH₃ (M = Mo, W)

Chloride displacement from Tp‘(CO)₂M⋮CCl (M = Mo, W (1); Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with LiMe₂Cu affords the methylcarbyne complex Tp‘(CO)₂M⋮CCH₃ (M = Mo (2), W (3)). Deprotonation of this methylcarbyne forms [Tp‘(CO)₂M=CCH₂]^- (M = Mo, W (4)), a nucleophilic vinylidene anion which reacts with a variety of substrates. Reaction of 4 with CH₃I yields Tp‘(CO)₂W⋮CCH₂CH₃ (5), while PhC(O)H yields Tp‘(CO)₂W⋮CCH₂CH(OH)(Ph) (8) and PhC(O)CH₃ yields Tp‘(CO)₂W⋮CCH₂C(OH)(CH₃)(Ph) (10). In the presence of base complex 8 undergoes elimination to form a conjugated vinyl carbyne complex Tp‘(CO)₂W⋮CCHCH(Ph) (11). Reaction of 4 with PhC(O)Cl and then base forms Tp‘(CO)₂W⋮CCH₂C(O)Ph (14), which rearranges in solution to a metallafuran complex, (15). Spectroscopic data suggests that a dinuclear intermediate, Tp‘(CO)₂W⋮CCH₂CPh(OH)CH₂C⋮W(CO)₂Tp‘ (13), is first formed from 4 and PhC(O)Cl before the addition of base produces the expected monomeric product, Tp‘(CO)₂W⋮CCH₂C(O)Ph (14).