LOW-COORDINATE CARBENE COMPLEXES OF NICKEL(0) AND PLATINUM(0)

The syntheses and characterizations of 2-coordinate homoleptic bis(carbene) adducts of 14-electron Ni(0) and Pt(0) are described. These carbene adducts are available directly from the reaction of the stable nucleophilic carbene 1,3-dimesitylimidazol-2-ylidene and the corresponding metal bis(cyclooctadiene) complexes. NMR data are consistent with the bis(carbene)-metal structures and suggest a higher degree of d pi-p pi back-donation from the metal relative to closely related Cu(I), Ag(I), and Au(I) complexes. The X-ray crystal structures of both the nickel-carbene and platinum-carbene adducts are reported. The metals exhibit an essentially linear 2-coordinate geometry with the imidazole rings twisted 53 degrees (Ni) and 51 degrees (Pt) relative to one another.