Comparison of mol-ecular structures of

Owing to the intra­molecular steric hindrance between the mutually cis-positioned 8-(di­methyl­phosphan­yl)quinoline (Me2Pqn) ligands, the nickel(II) complex of cis-[Ni(Me2Pqn)2]2+ shows a remarkable tetra­hedral distortion of the NiII coordination geometry. In contrast, the corresponding platinum(II) complex of cis-[Pt(Me2Pqn)2]2+ exhibits a typical square-planar PtII coordination center, but large envelope-type distortions of the five-membered chelate planes are observed.
The crystal structures of the complexes (SP-4-2)-cis-bis­[8-(di­methyl­phosphan­yl)quinoline-κ2 N,P]nickel(II) bis­(perchlorate) nitro­methane monosolvate, [Ni(C11H12NP)2](ClO4)2·CH3NO2 (1), and (SP-4-2)-cis-bis­[8-(di­methyl­phos­phan­yl)quinoline-κ2 N,P]platinum(II) bis­(tetra­fluoro­borate) aceto­nitrile monosolvate, [Pt(C11H12NP)2](BF4)2·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) Å and, the Pt—N bond lengths of 2, 2.123 (4) and 2.132 (4) Å, 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 NiII complex in 1 shows a tetra­hedral distortion of the coordination geometry, as parameterized by τ4 = 0.199 (1)°, while the PtII complex in 2 exhibits a typical square-planar coordination geometry [τ4 = 0.014 (1)°] with a large bending deformation of the ideally planar Me2Pqn 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).