Binuclear Complexes with an Aminocarbene-Cyclopropenylidene Unit as Bridging Ligand : Facile Migration of Carbonylmetal Fragments in Carbene Complexes

Abstract

The sequential reaction of the (dimethylamino)ethynylcarbene complexes [(CO)5MC(NMe2)CCH] (1a−c: M = W (a), Mo (b), Cr (c)) with BuLi, [M(CO)6], and CF3SO3CH3 affords homobinuclear complexes with an aminocarbene−cyclopropenylidene bridging ligand, (3a−c). Two isomeric heterobinuclear complexes (4xy and 4yx) are formed in the reaction of [(CO)5MC(NMe2)CCH] (1) with BuLi, [M‘(CO)6] (M ≠ M‘: W, Mo, Cr), and CF3SO3CH3. 4xy and 4yx differ in the relative distribution of the metals M and M‘: (4xy) and (4yx). The 4xy/4yx ratios obtained by the two different possible reaction sequences are similar. Complexes 4xy and 4yx do not interconvert. The reaction of cis-[(CO)4(Me3P)WC(NMe2)CCH] with BuLi, [W(CO)6], and CF3SO3CH3 likewise gives two isomers, (7) and (8). These results demonstrate the facile migration of carbonylmetal fragments along a carbon chain. The structures of the complexes 3b,c and 7 have been established by X-ray structural analyses.