2-METHOXYPHENYL PHOSPHITE COMPLEXES OF PLATINUM(0) AND NICKEL(0)

The compounds P(OC6H4OMe-2), 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(eta-2-norbornene)platinum, and [Pt(eta-2-C2H4){P(OC6H4OMe-2)3}2] 2 by the reduction of [PtCl2{P(OCH4OMe-2)3}2] in the presence of ethene or by adding of the phosphite to [Pt(eta-2-C2H)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(eta-2-alkene){P(OC6H4OMe-2)3}2] or [Pt(eta-2-alkyne){P(OC6H4OMe-2)3}2]. Reduction of [Ni(acac)2] (acac = acetylacetonate) with AlMe3 in the presence of ethene gives [Ni(eta-2-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(OCH4OMe-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.