NEW ICOSAHEDRAL HETEROMETALLIC NICKEL CARBONYL CLUSTERS CONTAINING BISMUTH

The new [Ni11Bi2(CO)18]n- (n =2 or 3) cluster anions have been obtained as a mixture by reaction of [Ni6(CO)12]2- with 0.5-0.7 equivalents of BiCl3 in tetrahydrofuran. Subsequent controlled oxidation or reduction of this mixture selectively affords the two anions. They have been isolated in the solid state as tetrasubstituted ammonium salts. The corresponding [Ni11Bi2(CO)18]4- tetraanion has only been obtained in solution by chemical or electrochemical reduction of the parent di- or tri-anion. All these compounds have been chemically and spectroscopically characterized, and the structure of [NEt4]3[Ni11Bi2(CO)18] has been ascertained by X-ray diffraction [orthorhombic, space group Pccn, a = 14.573(2), b = 19.638(4), c = 21.248(3) angstrom, Z = 4, R = 0.0501]. The geometry of the trianion is based on a nickel-centred Ni10Bi2(mu12-Ni)(CO)18 icosahedral core. Relevant average bond distances are Ni-Ni(intrapentagonal) 2.810 angstrom, Ni-Ni(interpentagonal) 2.506 angstrom, Ni-Ni(inner-outer) 2.595 angstrom, Bi-Ni(inner) 2.507 angstrom and Bi-Ni(outer) 2.819 angstrom. The corresponding di- and tetra-anions probably possess a closely related structure as shown by the electrochemical reversibility of their electron-transfer processess and by the similarity of the IR patterns of the three compounds.