Tungsten(0) and rhodium(I) complexes of a series of 2-(2′-halo)triarylphosphinines

Abstract

A series of halo substituted triarylphosphinines have been synthesised and coordinated to tungsten(0) and rhodium(I) to give [(2-(2′-halo)-triarylphosphinine)W(CO)₅] and [(2-(2′-halo)-triarylphosphinine)Rh(COD)Cl] respectively. The complexes have been examined by NMR and IR spectroscopy in an effort to elucidate the nature of the bonding between the phosphinines and the respective metal centre. The W(CO)₅(L) systems reveal restricted C–C bond rotation as evidenced by temperature-dependent ³¹P{¹H} NMR spectra. Thermodynamic barriers to the rotation are dependent upon the nature of the halide with ΔG^‡ values of 72.5 kJ mol⁻¹ and 50.8 kJ mol⁻¹ being obtained for the chloro- and fluoro-derivatives, respectively; activation barriers for the iodo- and bromo- derivatives were beyond the accessible temperature range of the NMR experiment.