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).