Dynamic nuclear magnetic resonance study of some ruthenium nitrosyl chalcogen complexes [Ru(NO)X₃(RR'E)₂] (X = Cl, Br; E = S, Se)

Abstract

The n.m.r. spectra of the complexes [Ru(NO)X₃L₂] (where X = Cl, Br; L = Et₂S,EtPhS, Pr₂S,(PhCH₂)₂S, Et₂Se EtPhSe) have been investigated over the temperature range 200-375 K. The resonance multiplet, assigned to the methylene protons, changes from a quartet at high temperatures to a coalesced peak and then a series of quartets at lower temperatures. The results may be explained by inversion about the S or Se atom; the spectra at low temperatures correspond to an ABX₃ spin system (for ethyl) and at high temperature to a A₂X₃ spin system. From computer simulation of the spectra the rates of inversion have been determined and hence the energy barrier to inversion (54-75 kJ mol^-1) and free energy of activation (54-79 kJ mol^-1).