Palladium complexes with the tripodal phosphine tris-(2-diphenylphosphinoethyl)amine. Synthesis and structure of trigonal, tetrahedral, trigonal bipyramidal, and square planar complexes

Abstract

The tripod-like ligand N(CH₂CH₂PPh₂)₃(tdpea) forms the palladium(0) trigonal complex [Pd(tdpea)]·0.5Me₂CO, (1), in which the apical nitrogen atom of the phosphine is unco-ordinated. This unsaturated species undergoes both addition (CO, SO₂) and oxidative-addition reactions (alkyl halides) to form respectively tetrahedral and trigonal bipyramidal complexes. The latter contain quadridentate tdpea. Complex (1) reacts with CO₂ or CS₂ in the presence of O₂ to form a square planar carbonate or dithiocarbonate derivative, with oxidation of a terminal PPh₂ group to OPPh₂. Crystal data for (1) are: a= 10.827(8)Å, α= 108.82(9)°, space group R3, and Z= 1. In the molecule the metal atom displays an unprecedented out-of-plane trigonal co-ordination. Crystal data for [Pd(tdpea)Me]I are: a= 10.570(7)Å, α= 106.10(7)°, space group R3, and Z= 1. The geometry of the [Pd(tdpea) Me]⁺ cation is trigonal bipyramidal, with the three-fold crystallographic axis passing through the nitrogen, the palladium, and the carbon atom.