Crystal structure of a (μ-bis(carbene))dimetal complex of tungsten

The (μ-bis(carbene))ditungsten complex, (CO)5W{(C(OCH2Ph)C(CH2C2H3)(Me)CH2CH2C(OCH2Ph)}W(CO)5 (1) is only the fifth such complex to be crystallographically characterized. The steric demands of one side of the bis(carbene) ligand gives rise to small, but statistically significant differences in the bonding parameters to W. The W=C distances are 2.195(4) and 2.171(6)A. The carbonyltrans to the longest W=C bond has the shortest of the ten W-CO separations (1.994(5)A) and the longest C≡O bond length (1.156(6)A). The planes defined by the two carbene groups have a dihedral angle of 44.5°.