Deuteron Magnetic Resonance of NiSiF6·6D2O and NiSnCl6·6D2O

Abstract

Abstract Deuteron magnetic resonance study was made on single crystals of NiSiF6·6D2O and NiSnCl6·6D2O. Deuteron quadrupole coupling tensors were determined at various temperatures. In NiSiF6·6D2O, the quadrupole coupling at −116°C is that of stationary D2O, at 23°C and at 70°C that of D2O under rapid 180°-flip motion and at 150°C that of rapid Ni(D2O)62+ reorientation. The eqQ⁄h values at −116°C, 238.3±1.3 kc and 235.7±1.9 kc do not appear to show marked effect of strong coordination. In NiSnCl6·6D2O, the quadrupole coupling corresponding to D2O under 180°-flip motion is observed at −53°C, at 25°C, and at 55°C. Spectra corresponding to a stationary D2O are not observed even at 77 °K. From the orientation of quadrupole tensors probable crystal structures of these compounds are proposed. Line width transitions were observed from which the reorientation rate was derived. The estimated activation energies of the 180°-flip motion of D2O are 7.6 and 4.3 kcal/mol in the fluosilicate and chlorostannate, respectively, and that of Ni(D2O)62+ reorientation in the fluosilicate is 19 kcal/mol. Additional measurements of 19F and 1H resonances indicate the setting in of the SiF62− reorientation at −110°–−120°C in NiSiF6·6H2O, and that of the Ni(H2O)62+ reorientation in the chlorostannate at approximately the same temperature as the fluosilicate.