SYNTHESIS, SPECTRAL AND MAGNETIC STUDIES ON MIXED-LIGAND COMPLEXES M(DIAFO)(2)(NCS)(2) AND M(DIAFH)(2)X(2)(M=FE-II, CO-II, NI-II) - THE CRYSTAL-STRUCTURE OF CO(DIAFO)(2)(NCS)(2)

A series of mixed-ligand complexes of group VIII metals, M(DIAFO)(2)(NCS)(2) and M(DIAFH)(2)X(2) (M = Fe-II, Co-II, Ni-II, X = NCS-, Cl-) with the 3,3'-bridged derivative of 2,2'-bipyridyl (bipy) (1) were prepared, where DIAFO (2) and DIAFH (3) are 4,5-diazafluoren-9-one and 4,5-diazafluoren-9-hydrazone, respectively. These complexes were investigated by i.r., u.v.-vis-near i.r. spectroscopy and by variable-temperature magnetic susceptibility measurements. The electronic spectra show that the two ligands exert a field strength far removed from the Fe-II cross-over value. All the complexes are paramagnetic, following the Curie-Weiss law in the 77-300 K range. A typical crystal structure of Co(DIAFO)(2)(NCS)(2) for these compounds was determined with orthorhombic, space group Pcan, a = 10.377(5) Angstrom b = 13.289(6) Angstrom c = 16.629(7) Angstrom, V = 2293(2) Angstrom(3), D-c = 1.563 g cm(-3), F(000) = 1091.74, Z = 4, R = 0.043, R(infinity) = 0.047. Steric effects are thought to be operative in both ligands studied, but are weaker than those of the typical bidentate diimine ligand bipy.