METAL-CENTERED C-C COUPLING OF NITRILES WITH 1-AZAALLYL LIGANDS - SYNTHESIS AND STRUCTURE OF BETA-DIIMINATO COMPLEXES OF TUNGSTEN

An efficient procedure is reported for the synthesis of beta-diiminato complexes starting from the readily accessible eta(3)-1-azaallyl complex Cp*(CO)(2)W(eta(3)-CH2 - CH - NEt) (1). The thermal reaction of 1 with nitriles RCN (R = Me, Ph) yields, by insertion of the nitrile into the metal-azaallyl-carbon bond, the beta-diiminato complexes Cp*(CO)(2)W[N(H)C(R)C(H)C(H)NEt] (2a: R = Me; 2b: R = Ph). The solid-state structure of 2a was determined by a single-crystal X-ray diffraction study. It reveals a ''four-legged piano stool'' complex composed of a Cp*(CO)(2)W-fragment and a N,N-chelated beta-diiminato ligand. Bond distances and angles within the organic ligand indicate pi-electron delocalization, as observed for the isoelectronic beta-diketonates.