Synthesis and structure of heteroleptic and homoleptic thiomethyl nickel complexes

Thiomethyl nickel complexes [Ni(CH(2)SR)(2)(PBu(3))(2)] (R = Me (1a), (t)Bu (1b), Ph (1c)) and the homoleptic derivatives [{Li(Et(2)O)}(2)Ni(CH(2)S(t)Bu)(4)] (2), [Li(2)Ni(CH(2)SMe)(4)] . x thf (3a) and [Li(2)Ni(CH(2)SPh)(4)] . x Et(2)O (3b) were synthesized by the reaction of nickel halide phosphine complexes with the appropriate thiomethyl lithium compounds LiCH(2)SR in a molar ratio of 1/2 and 1/4, respectively. The molecular structures (X-ray) of the diamagnetic heteroleptic derivatives 1 exhibit C(i) symmetry with square-planar NiC(2)P(2) units. The ligands are arranged in trans-position. The complexes 1 were characterized by microanalysis and by NMR spectroscopy. The tert-butylthiomethyl complex 2 is stable at room temperature (T(dec.) similar to 60-66 degrees C) whereas the methyl- and phenyl-thiomethyl complexes 3a and 3b are decomposed already at -10 to -20 degrees C. The molecular structure (X-ray) of complex 2 shows a slightly distorted planar arrangement of the four methylene carbon atoms and nickel (d(Ni-C) = 1.944(3)-2.004(3) Angstrom). The lithium atoms are distorted tetrahedrally coordinated by two sulfur atoms, one oxygen atom (Et(2)O) and one methylene carbon atom. The short Li-S distances (2.461(6)-2.535(5) Angstrom) indicate strong lithium-sulfur interactions.