RAMAN-SPECTROSCOPIC AND AB-INITIO QUANTUM-CHEMICAL INVESTIGATIONS OF MOLECULES AND COMPLEX-IONS IN THE MOLTEN SYSTEM CSCL-NBCL5-NBOCL3

Raman spectroscopy has been used to study the liquid system CsCl-NbCl5 -NbOCl3 at temperatures between 340 and 650 degrees C, Molten NbOCl3 s hows Raman bands typical of bridging and terminal oxygen. In the basic regions of the system the ions NbCl6-, NbOCl52-, and NbOCl4- have bee n identified, In the acidic region, polymeric ions with bridging oxyge n probably coexist with ions with terminal oxygen. The structure of Nb Cl6-, NbOCl52-, and NbOCl4- have been verified by and the interpretati on of their spectra assisted with ab initio SCF and CASSCF calculation s. SCF calculations have also been performed for NbCl5 and NbOCl3 and VOCl3, VOCl4-, and VOCl52- for comparison. In the binary CsCl-NbOCl3, when x(CsCl) > 0.5, the equilibrium NbOCl4- + Cl- = NbOCl52- is establ ished. This is also verified by quantum chemical calculations.