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.