Mono and dinuclear palladium complexes of o-alkyl substituted arylphosphane ligands: Solvent-dependent syntheses, NMR-spectroscopic characterization and X-ray crystallographic studies

摘要

Palladium(II) chloride complexes of o-alkyl substituted phosphanes were prepared in various solvents with the phosphatic ligands o-methylphenyldiphenylphosphane, o-ethylphenyldiphenylphosphane, o-isopropylphenyldiphenylphosphane, o-cyclohexylphenyldiphenylphosphane and o-phenylphenyldiphenylphosphane. The structures of the complexes were characterized by H-1 NMR and P-31 NMR spectroscopy and elemental analysis. The X-ray structures of PdCl2(o-methylphenyldiphenylphosphane)(2), PdCl2(o-isopropylphenyldiphenylphosphane)(2), PdCl2(o-cyclohexylphenyidiphenylphosphane)(2), PdCl2(o-phenylphenyldiphenylphosphane)(2), [PdCl2(o-methylphenyldiphenylphosphane)](2), [PdCl2(o-ethylphenyldiphenylphosphane)](2) and [PdCl2(o-cyclohexylphenyldiphenylphosphane)](2) were also determined. We report a systematic, solvent-dependent method to prepare palladium(II) complexes of the aryl phosphines o-methylphenyldiphenylphosphane, o-cyclohexylphenyldiphenylphosphane and o-phenylphenyldiphenylphosphane with a desired nuclearity. We demonstrated that chlorinated solvents promote the formation of dinuclear chlorine-bridged palladium complexes for all five ligands. The ligands preferentially form mononuclear palladium complexes in other solvents where the starting materials are only weakly soluble in the solvent. (c) 2007 Elsevier B.V. All rights reserved.