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

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