DARSTELLUNG UND CHARAKTERISIERUNG DER WOLFRAM-ACETYLENKOMPLEXE η5-ArW(CO)(R1C2R2)R UND η5-ArW(CO)(R1C2R2)COR (Ar = C5H5, C5H4Me, C5Me5; R1, R2 = H, Me, Ph; R = Me, Et, nPr, nBu, Ph)

Article abstract of DOI:10.1016/0022-328X(85)87273-9

The photoinduced reaction of the complexes η-ArW(CO)3R (I) (Ar = C5H5, C5H4Me, C5Me5; R = Me, Et ⁿPr, ⁿBu, Ph) with symmetrical or asymmetrical acetylenes R¹C2R² (R¹, R² = H, Me, Ph) in pentane solution at -30 deg C yields primarily the acetylene acyl complexes η⁵-ArW(CO)(R¹C2R²)COR (II).Upon warming, complexes II undergo dismutation to form the acetylene alkyl complexes η⁵-ArW(CO)(R¹C2R²)R (III) and the metallacyclic alkenylketone complexes (IV).The alkyl complexes III add two-electron ligands, such as carbon monoxide, phosphanes and phosphites, even at -100 deg 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.