Darstellung und charakterisierung der wolframacetylenkomplexeη 5ArW(CO)(R 1C 2R 2)R und η 5-ArW(CO)(R 1C 2R 2)COR (Ar = C 5H 5, C 5H 4Me, C 5Me 5; R 1, R 2 = H, Me, Ph; R = Me, Et, nPr, nBu, Ph)

Abstract

The photoinduced reaction of the complexes η 5-ArW(CO) 3R (I) (Ar = C 5H 5, C 5H 4Me, C 5Me 5; R = Me, Et, nPr, nBu, Ph) with symmetrical or asymmetrical acetylenes R 1C 2R 2 (R 1, R 2 = H, Me, Ph) in pentane solution at −30°C yields primarily the acetylene acyl complexes η 5-ArW(CO)R 1C 2R 2COR (II). Upon warming, complexes II undergo dismutation to form the acetylene alkyl complexes η 5-ArW(CO)(R 1C 2R 2)R (III) and the metallacyclic alkenylketone complexes η 5-Ar(CO) 2 W[R 1CCR 2C(O )R] (IV). The alkyl complexes III add two-electron ligands, such as carbon monoxide, phosphanes and phosphites, even at − 100°C to give acyl derivatives of the type II. The alkyne complexes II and III represent 18-electron species with the acetylene acting as a four-electron ligand; therefore the alkyl ligands containing hydrogen in the β-position with respect to the metal are surprisingly stable towards photoinduced β-hydrogen elimination. The acyl ligands in II show carbene-like properties giving rise to a zwitterionic character in these compounds.