Oxidative formation of phosphinyl radicals from a trigonal pyramidal terminal phosphide Rh(i) complex, with an unusually long Rh–P bond

Abstract

A rhodium complex containing a tetrapodal triolefin ligand (trop₃P) and a phosphanyl ligand (PPh₂⁻) has been prepared and characterised. The special structural confinements of the tetradentate ligand impose an unusually long Rh–PPh₂ bond. Chemical oxidation of the complex with FcOTf affords [Rh(OTf)(trop₃P)] and plausibly phosphanyl radicals, which react instantly with a spin trap reagent forming a nitroxide-based persistent radical, undergo HAT with silanes or dimerise to the corresponding diphosphine (PPh₂)₂. Chemical oxidation with a peroxide leads to complex [Rh(POPh₂)(trop₃P)] which is photolabile and loses the Ph₂PO moiety upon irradiation with UV/Vis light in CH₂Cl₂.