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

Abstract

Reaction of [(CO) 5 W Ä/C(NMe 2) Ã/C Å/CH] (1a) with n-BuLi and [M(CO) 6 ] (M0/W, Cr, Mo) in THF and chromatography on silica affords the 3-dimethylamino cyclobuten-2-on-1-ylidene tungsten complex [(CO) 5 W Ä/ / ae C ÃCH ÄC(NMe 2) ÃC /(Ä/O)] (2). Complex 2 is also isolated, after chromatography, from the reaction of [(CO) 5 M Ä/C(NMe 2) Ã/C Å/CH] (M 0/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 Et 2 O Á/THF (5:1) a binuclear nonacarbonyl m-3-dimethylaminocyclobuten-2-on-1-ylidene complex [(CO) 5 W{ m-/ ae CÃCH ÄC(NMe 2)ÃC /(Ä/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.