Multinuclear NMR and crystallographic study of diorganotin valproates - Part II

Abstract

The reactions of SnR2Cl2 {R = Me, Bu and Ph} and sodium valproate, NaO2CCH(CH2CH2CH3)2, NaOVp yielded three diorganotin valproates [{(Me2SnOVp)2O}2] (1), [{(Bu2SnOVp)2O}2] (2) and [{PhSn(O) OVp}6] (3). These stannoxanes have been authenticated in terms of infrared, 1H and 13C NMR, and solution- and solid-state 119Sn NMR and 119Sn Mössbauer spectroscopy. In addition the crystallographic structures of complexes (1)–(3) have been determined by X-ray diffraction. Complexes (1) and (2) displayed two major signals in the 119Sn NMR spectra in solution corresponding to the exo and endocyclic SnR2 moiety of the stannoxanes. Other minor resonances have been also observed due to dynamic processes in solution. However in the 119Sn MAS-NMR experiments only two down field signals were detected for complex (1), according to the presence of the exo and endocyclic organotin fragments, but with different resonance in comparison with the chemical shift obtained in solution. On the other hand little difference was observed in the 119Sn chemical shift of complex (3) since only one resonance was detected in solution- or in the solid-state experiments, and the signals are very close to each other.