title: Anionic Fischer-type carbene complexes as bidentate (N,O) ligands.
abstract: New polynuclear complexes, (L1)3M2 [M2 = Cr(III) (4a,4b), Fe(III) (5), Co(III) (8)], (L1)2M2(L2)2 [M2 = Co(II) (7), Ni(II) (9)], (L1)2M2(O)L2 [M2 = V(IV) (6)] and L1M2Cp2 [M2 = Ti(III) (10)] with L1 = (CO)5M1=C[C=NC(CH3)=CHS](O-)(M1 = Cr or W) and L2 = 4-methylthiazole or THF, are described. The molecular structures of these complexes determined by X-ray diffraction show that the Fischer-type carbene complexes act as bidentate ligands towards the second metal centre, coordinating through C(carbene)-attached O-atoms and imine N-atoms of the thiazolyl groups to form five-membered chelates with the oxygen atoms in the mer configuration. Isostructural complexes have similar characteristic band patterns in their far-IR spectra. Cyclic voltammetry of selected complexes reveals the oxidation of the carbene complex ligand between 1.01 and 1.29 V. Oxidation of the central metal (M2) takes place at 0.56 and 0.86 V for 7 and 9, respectively. Three stepwise reductions of Cr(III) to Cr(0) occur for 4a and 4b in the region -0.51 to -1.58 V. These new ligand types and other variants thereof should find application in ligand design with the first metal -- and other ligands attached thereto -- in the carbene complex ligand, playing an important role.
authors.affiliation: Department of Chemistry, University of Stellenbosch, Private Bag X1, Matieland 7602, Stellenbosch, South Africa. hgr@sun.ac.za
authors.forename: Helgard G
authors.initials: HG
authors.lastname: Raubenheimer
authors.forename: Aletta
authors.initials: A
authors.lastname: du Toit
authors.forename: Maria
authors.initials: M
authors.lastname: du Toit
authors.forename: Jin
authors.initials: J
authors.lastname: An
authors.forename: Lizette
authors.initials: L
authors.lastname: van Niekerk
authors.forename: Stephanie
authors.initials: S
authors.lastname: Cronje
authors.forename: Catharine
authors.initials: C
authors.lastname: Esterhuysen
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Crouch