Synthesis and Crystal Structure of Ternary SulfidesA3MS4withA=Na, Rb andM=Nb, Ta

Abstract

The new ternary sulfides Na3MS4and Rb3MS4(M=Nb, Ta) were prepared from tantalum nitride or niobium powder in the respective alkali metal polysulfide melt. Both sodium sulfides crystallize in form of yellow (Nb) or yellow-orange (Ta) needles in the orthorhombic space groupFdd2 withZ=32 anda=27.3034(4) Å,b=28.4662(1) Å, andc=7.9642(1) Å,R/Rw=0.024/0.048 forM=Nb anda=27.2322(2) Å,b=28.4264(2) Å, andc=7.9634(6) Å,R/Rw=0.066/0.177 forM=Ta. The rubidium sulfides were obtained as yellow (Nb) and orange (Ta) crystals with irregular shape. They crystallize in the orthorhombic space groupPnmawithZ=4 anda=9.6109(6) Å,b=11.1013(7) Å, andc=9.6390(6) Å,R/Rw=0.030/0.072 forM=Nb anda=9.6084(5) Å,b=11.1067(6) Å, andc=9.6426(5) Å,R/Rw=0.031/0.070 forM=Ta. The structures of all four compounds are built by stacking isolatedMS3-4units with the alkali metal ions. © 1998 Academic Press.