Preparation and Properties of Stable Alkylcopper(I) Complexes Containing Tertiary Phosphine Ligands

Abstract

A variety of stable alkylcopper(I) complexes of composition RCuL_n (n=1–3) containing various monodentate tertiary phosphine ligands (L), such as triphenylphosphine, diphenylmethylphosphine, dimethylphenylphosphine, tributylphosphine, triethylphosphine, and tricyclohexylphosphine have been prepared by the reactions of copper-(II) acetylacetonate, dialkylaluminium monoethoxide, and the tertiary phosphines. Similar reactions employing 1,2-bis(diphenylphosphino)ethane(dpe) give (RCu)₂(dpe)₃. The complexes have been isolated and characterized by elemental analysis, determination of molecular weight, chemical reactions, IR and NMR spectroscopy. All the isolated complexes show considerable thermal stability compared with alkylcopper compounds without phosphine ligand indicating the marked contribution of these phosphine ligands to the stabilization of the copper-carbon bond. The dpe-coordinated alkylcopper complexes are thermally stable in the solid state but readily decompose in solution with hydrogen abstraction accompanied by scission of the C–P bond of dpe to give Ph₂PCu-(dpe), Ph₂PCH=CH₂, and alkane. These alkylcopper complexes initiate the polymerization of vinyl monomers such as acrylonitrile, methacrylonitrile, methyl acrylate, and methyl methacrylate. Alkyl halides and acyl halides react with the alkylcopper complexes to give cross-coupling products of alkyl groups and alkyl-acyl groups.