ORGANOMETALLIC NICKEL(II) COMPLEXES WITH SUBSTITUTED BENZONITRILE LIGANDS, SYNTHESIS, ELECTROCHEMICAL STUDIES AND NONLINEAR-OPTICAL PROPERTIES - THE X-RAY CRYSTAL-STRUCTURE OF [NI(ETA(5)-C5H5)(P(C6H5)(3))(NCC6H4NH2)][PF6]

A new family of organometallic Ni(II) benzonitrile derivatives bearing strong donor substituents of general formula [Ni(eta(5)-C5H5){P(C6H5) (3)}NCC6H4R][PF6] (R = NH2, N(CH3)(2), C6H5, OCH3, H, F) has been synt hesized. A structural study by X-ray diffraction of the compound with R = NH, showed crystallization on the centrosymmetric monoclinic space group, P2(1)/n, with a quasi planar structure of the coordinated nitr ile. First and second hyperpolarizabilities evaluated by hyper-Rayleig h scattering and Maker fringe techniques showed essentially the same v alues for the complexes and the uncoordinated chromophores. Theoretica l studies by the extended Huckel method found a small amount of pi del ocalization due to the cancelling effects on the interaction of the me tal fragment orbitals with pi and pi nitrile orbitals. (C) 1998 Elsev ier Science S.A.