Assignment of the proton magnetic resonance spectra of some tris-(diethylphenylphosphine) complexes of Re(III), Re(IV), Ir(III) and Rh(III)

Abstract

Proton resonance spectra are reported for ReCl₃(PMe₂Ph)₃, ReCl₃(PEt₂Ph)₃, ReCl₄(PEt₂Ph)₂, IrCl₃(PEt₂Ph)₃, RhCl₃(PEt₂Ph)₃ and for the free phosphine ligand. The spectra are assigned on the basis of diamagnetic behaviour for Ir(III) and Rh(III), paramagnetic behaviour for Re(III) and Re(IV), and meridial octahedral structures (C _2v symmetry) for the M(III) complexes. Spectral peculiarities are: (i) ‘virtual coupling’ of protons in alkyl groups to the two mutually trans phosphorus atoms in the diamagnetic complexes; (ii) large shifts arising from contact or pseudo contact mechanism in the paramagnetics; (iii) lack of phosphorus-hydrogen and small (<7 c/s) hydrogen-hydrogen couplings in the paramagnetics, and (iv) inequivalent methylene protons in the ethylphosphine complexes.