Mono- and binuclear 3-amino cyclobuten-2-one complexes of tungsten—facile migration of pentacarbonylmetal fragments in carbene complexes

Reaction of [(CO)5WC(NMe2)CCH] (1a) with n-BuLi and [M(CO)6] (M=W, Cr, Mo) in THF and chromatography on silica affords the 3-dimethylamino cyclobuten-2-on-1-ylidene tungsten complex [(CO)5W(O)] (2). Complex 2 is also isolated, after chromatography, from the reaction of [(CO)5MC(NMe2)CCH] (M=Cr [1b], Mo [1c]) with n-BuLi and [W(CO)6] in THF. These results demonstrate the facile migration of carbonylmetal fragments along a carbon chain. When 1a is sequentially treated with n-BuLi, [W(CO)6], and water in Et2O–THF (5:1) a binuclear nonacarbonyl μ-3-dimethylamino-cyclobuten-2-on-1-ylidene complex [(CO)5W{μ-(O)}W(CO)4] (6) is produced. In solution 6 decomposes to give 2. The structures of the complexes 2 and 6 were established by X-ray structure analyses.