Mononuclear palladium(II) complexes with the phenylselenolato ligand. The crystal and molecular structure of trans-[Pd(SePh)2(P(n-Bu)3)2]

Synthesis and Properties of Palladium Diselenolenes: X-ray Crystal Structures of [Pd{SeC(R1)C(R2)Se}(PBu3)2] [R1, R2 = (CH2)n, n = 4, 5, 6]

The reaction between [Pd(2)(dba)(3)] (dba = dibenzylideneacetone), tributylphosphine, and a bis(cycloalkeno)-1,4-diselenin leads to either a mononuclear diselenolene [Pd[SeC(R(1))=C(R(2))Se](PBu(3))(2)] or a dinuclear diselenolene [Pd(2)[SeC(R(1))=C(R(2))Se](2)(PBu(3))(2)] [R(1), R(2) = (CH(2))(n), n = 4, 5, 6] depending on the stoichiometry employed. Treatment of the dinuclear diselenolenes with 1,2-bis(diphenylphosphino)ethane (dppe) provides a high-yielding route to the mononuclear species [Pd[SeC(R(1))=C(R(2))Se](dppe)]. All new compounds have been characterized by standard spectroscopic and analytical techniques, in particular by multinuclear NMR spectroscopy; the structure of each of the mononuclear tributylphosphine complexes has been determined by X-ray crystallography. Computational studies show that the observed asymmetry of the diselenolenes in the solid state is a result primarily of intramolecular repulsive interactions between the ligands.