New phosphine ligands with the OPN donor configuration

Abstract

New, functionalised phosphines with an OPN donor set which are potentially capable of square planar co-ordination were synthesized by stepwise introduction of the oxygen and nitrogen functional substituents to phosphorus. The secondary phosphines (phenyl)(tetrahydrofurfuryl)phosphine, 1, and [2-(1,3-dioxolan-2-yl)ethyl](phenyl)phosphine, 2, were first prepared before the introduction of the nitrogen donor substituents. The OPN phosphines (phenyl)(D¹)(D²)phosphine {D¹ = tetrahydrofurfuryl, D² = 2-pyridylmethyl or pyridyl; D¹ = 2-(1,3-dioxolan-2-yl)ethyl, D² = 2-pyridylmethyl}, 3–5, were obtained. This approach was not appropriate for the preparation of an OPN ligand with an ester functionality. Therefore the synthesis of methyl 3-[(phenyl)(2-pyridylmethyl)phosphino]propanoate, 7, was achieved via a radical induced coupling of methyl acrylate to (phenyl)(2-pyridylmethyl)phosphine 6. All new ligands, 1–5, 7, were characterised by ¹H, ¹³C and ³¹P NMR spectroscopy. The methods developed allowed the ligands to be synthesized in high yields and purity such that further purification was generally unnecessary for subsequent applications.