X-Ray, NMR, and NQR Investigations of the Crystal Structure and Charge Distribution of Sodium Tetrachloroaluminate, NaAlCl4

Abstract

Abstract On single crystals of NaAlCl4 the NMR- and NQR-spectra of 23Na, 27Al, and 35Cl were studied at room temperature. The crystal structure of NaAlCl4 has been refined. A comparison of the NMR (NQR) data with the crystal structure data shows that the electric field gradients (EFG) at the chlorine sites are mainly determined by the partial covalency of the Al-Cl bond, whereas the EFG at the aluminum sites is determined by the small deviations of the AlCl4 ion from tetrahedral symmetry and by the influence of the lattice. ∣ e2 q Q/h ∣ (23Na) proves the dominant ionic character of sodium in the lattice. The experimental results for the crystal structure show minor deviations from Baenziger's data. The NMR (NQR) data at T=22 °C are [atom (∣e2 q Q/h ∣ / MHz; η)]: 23Na (1.1117±0.0012; 0.2153 + 0.0005); 27Al (1.4895±0.0012; 0.3375±0.0011) ; 35ClI (23.033±0.030; 0.182 ±0.025); 35ClII (22.520 ±0.010; 0.270 ± 0.005) ; 35ClIII (21.646 ±0.003; 0.315±0.007); 35ClIV (22.410±0.016; 0.197±0.010).