The sequential reaction of the (dimethylamino)ethynylcarbene complexes [(CO)5MC(NMe2)C⋮CH] (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)C⋮CH] (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)C⋮CH] 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.
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.
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