Comparison of molecular structures of cis-bis[8-(dimethylphosphanyl)quinoline]nickel(II) and -platinum(II) complex cations

The crystal structures of the complexes (SP-4-2)-cis-bis[8-(dimethylphosphanyl)quinoline-kappa N-2,P]nickel(II) bis(perchlorate) nitromethane monosolvate, [Ni(C11H12NP)(2)](ClO4)(2)center dot CH3NO2 (1), and (SP-4-2)-cis-bis[8-(dimethylphosphanyl)quinoline-kappa N-2,P]platinum(II) bis(tetrafluoroborate) acetonitrile monosolvate, [Pt(C11H12NP)(2)](BF4)(2)center dot C2H3N (2), are reported. In both complex cations, two phosphanylquinolines act as bidentate P,N-donating chelate ligands and form the mutually cis configuration in the square-planar coordination geometry. The strong trans influence of the dimethylphosphanyl donor group is confirmed by the Ni-N bond lengths in 1, 1.970 (2) and 1.982 (2) angstrom and, the Pt-N bond lengths of 2, 2.123 (4) and 2.132 (4) angstrom, which are relatively long as compared to those in the analogous 8-(diphenylphosphanyl)quinoline complexes. Mutually cis-positioned quinoline donor groups would give a severe steric hindrance between their ortho-H atoms. In order to reduce such a steric congestion, the Ni-II complex in 1 shows a tetrahedral distortion of the coordination geometry, as parameterized by tau(4) = 0.199 (1)degrees, while the Pt-II complex in 2 exhibits a typical square-planar coordination geometry [tau(4) = 0.014 (1)degrees] with a large bending deformation of the ideally planar Me(2)Pqn chelate planes. In the crystal structure of 2, three F atoms of one of the BF4- anions are disordered over two sets of positions with refined occupancies of 0.573 (10) and 0.427 (10).