2-Methoxyphenyl phosphite complexes of platinum(0) and nickel(0)

Abstract

The compounds P(OC₆H₄OMe-2)₃ and P(OC₆H₄OMe-2)(OC₆H₄Me-4)₂ have been prepared. The platinum(0) complex [Pt{P(OC₆H₄OMe-2)₃}₃]1 can be made by the reduction of [PtCl₂{P(OC₆H₄OMe-2)₃}₂] in the presence of the phosphite or by addition of the latter to tris(η²-norbornene)platinum, and [Pt(η²-C₂H₄){P(OC₆H₄OMe-2)₃}₂]2 by the reduction of [PtCl₂{P(OC₆H₄OMe-2)₃}₂] in the presence of ethene or by adding of the phosphite to [Pt(η²-C₂H₄)₃]. The crystal structures of the ligand P(OC₆H₄OMe-2)₃ and complex 2 have been determined and the effect of co-ordination on the conformation of the phosphite substituents is discussed. The ethene ligand in 2 is readily substituted by other alkenes and alkynes to give complexes 3–9 of the general type [Pt(η²-alkene){P(OC₆H₄OMe-2)₃}₂] or [Pt(η²-alkyne){P(OC₆H₄OMe-2)₃}₂]. Reduction of [Ni(acac)₂](acac = acetylacetonate) with AlMe₃ in the presence of ethene gives [Ni(η²-C₂H₄){P(OC₆H₄OMe-2)₃}₂]10. The air-sensitive complex [Ni{P(OC₆H₄OMe-2)₃}₃]11 can be generated in solution by treatment of [Ni(cod)₂](cod = cycloocta-1,5-diene) or 10 with the phosphite ligand. The tetrahedral complex [Ni{P(OC₆H₄OMe-2)(OC₆H₄Me-4)₂}₄]12 is readily made from [Ni(cod)₂] and the phosphite. The catalytic activity of 11 and 12 for the monohydrocyanation of buta-1,3-diene is discussed in relation to similar well known catalysts and it is concluded that the methoxy groups inhibit the catalysis probably by a combination of steric hindrance and weak co-ordination of the ether oxygen.