The synthesis and properties of the hexachloroniobates and hexachlorotantalates of Na, K, Rb, and Cs

Abstract

CsTaCI, were synthesized in a closed system by the reaction of NbCI, o r TaCI, vapour with solid alkali-metal chloride as follows where M is N b or Ta, and A is Na, K , Rb, o r Cs. The X-ray powder diffraction patterns o f these compounds were obtained. Temperatures of various phase transformations were determined cryoscopically.

Drop calorimetry of the compounds NbCl5, TaCl5, RbNbCl6, CsNbCl6, RbTaCl6, and CsTaCl6

“…Crystal structures of the-AMC16 type compounds, where A is an alkali metal like Na, K, Rb, and Cs, and M is either Nb or Ta, and parts of the phase diagrams of the AC1-MC15 type binary systems have also been reported by several investigators (1,(5)(6)(7)(8)(9).…”

“…The preparation of anhydrous NbC15 and TaC15 having a purity better than 99.99% by weight and the synthesis of the stoichiometric AMC16type compounds having a purity better than 99.8% by weight, have been described elsewhere (1,2). ' The stoichiometry of each complex compound was determined from the weight gain of the alkali chloride when it is reacted with either NbC15 or TaC15 vapours.…”

“…The calorimeter proper was calibrated with synthetic sapphire certified by the U.S. Bureau of Standards. Its enthalpy content is known to be the following function of temperature (12), [1] HT -Ho = 82.1461 + 1.7106 X T~ -46.9949 X log lo T + 0.1485704 T (in kJ mol-I) where T is in Kelvin.…”

“…The complex compounds NaNbC16, NaTaC16, KNbC16, KTaC16, RbNbC16, RbTaCI6, CsNbC16, and CsTaC16 have been synthesized in this laboratory by the reaction of NbCI, or TaCl, vapours with the respective alkali metal chlorides, in closed reactors, under specific temperature and vapour pressure conditions. The preparation method has been given elsewhere (1). X-ray diffraction patterns were also determined and temperatures for phase transformations were measured by the cooling curve technique.…”