Methylnickel compounds with chelating anionic ligands. Crystal and molecular structures of methyl(trimethylphosphine)nickel oxinate and oxalate dimer

Abstract

Several new methyl-nickel(II) compounds NiMe- X(PMe 3) [X=8-hydroxyquinolate, 1; X=1/2[O 2C(CH 2) n CO 2), 2: n=0; 3: n=1; 4: n=2; 5: n=3; 6: n=4] were prepared by reacting [NiMe(PMe 3)(OMe)] 2 and the corresponding acid. Compound 1 crystallizes in the space group P 1 with a=8.868(1), b=9.303(2), c=8.452(1) Å, α=94.29(1)°, β= 105.85(1)°, γ=82.63(1)°, V=671.8(1) Å 3, Z= 2. Final discrepancy indices are R=0.0291 and R w =0.0303 for 2255 independent data ( I>3σ( I)). The coordination geometry around nickel is square planar. The NiP and NiC distances of 2.125(1) and 1.917(2) Å are on the shortest range of the usually observed values, while the NiO and NiN values of 1.923(2) and 1.953(2) Å are on the upper one. The oxygen atom of the oxinate ligand is trans to the methyl group. Compound 2 crystallizes in the space group P2 1/ n with a=9.266(1), b=11.113(2), c=8.169(2) Å, β=93.46(2)°, V=839.5 Å 3, Z=4. The final R values are R=0.0325 and R w= 0.0334 for 1221 independent data ( I>3σ( I)). The molecule shows two nickel atoms bridged by the oxalato group acting as a bidentate ligand to both metals (NiO1=1.990(3) and NiO2=1.961(3) Å). The dimer possesses a crystallographic center of symmetry, which is located in the middle of the oxalato CC bond. The geometry about each metal is square planar, the coordination sphere being completed by the methyl and trimethylphosphine ligands. Compounds 3 6 have been characterized by IR spectroscopy, together with compounds 4a 6a obtained by reaction with PMe 3 in excess.