79,81Br NQR nuclear quadrupole resonance study of the hexabromocadmate (II)-ion, [CdBr 6] 4−

Abstract

The 79,81Br NQR frequencies of coordination compounds A 4CdBr 6, A = NH 4, ND 4, and Rb, and of M 2CdBr 6, M = Mg(H 2O) 6, were studied as a function of temperature. ν( 79Br) = f(T) of the ammonium compound passes a maximum which is considerably influenced in temperature and frequency by the exchange H → D. A positive temperature coefficient is observed for ν( 81Br) in (Mg(H 2O) 6) 2CdBr 6 throughout the whole range of T studied. This behaviour is discussed as arising from the dynamic of the ions NH 4 and Mg(H 2O) 6, respectively, and the influence of the hydrogen bonds NH…Br and OH…Br on the electric field gradient at the bromine sites.