Rubidium iodide triiodide hexaiodobismuthate(III) dihydrate

Abstract

RbsI(13)(BiI6) (H20)2, trigonal, R 3m; hexag- onal axes: a = 23.380 (6), c = 14.959 (2) A; D O = 3.9 (1), Z = 9, Dc --- 4.097 g cm-3; R = 0.104 for 878 reflexions II > 2.5o(I)1. The structure contains rubidium cations, octahedral hexaiodobismuthate(III) anions, iodide anions, linear symmetrical triiodide anions and water molecules. Introduction. This work is part of a systematic study of bromo- and iodobismuthates(Ill) (see the preceding paper). It was thought interesting to synthesize a com- pound containing isolated hexaiodobismuthate(III) anions and to determine its crystal structure. The com- pound was prepared with a large excess of RbI, because it is possible that the iodide anions present in the structure might prevent the linking of BiI 6 oc- tahedra into the polynuclear species usually found in iodobismuthates(llI). Black crystals were grown by very slow evaporation from an aqueous solution, ob- tained by dissolving Bi(OH)3 and Rb2CO 3 in 1:3 molar ratio in a dilute HI solution. During evaporation, some of the iodide ions in the solution were oxidized by air oxygen to triiodide ions (I~). The chemical formula was established by means of standard analytical methods {found: Bi (complexometric) 10.62%, Rb (as RbB(C6Hs)41 21.90%, total I (as AgI) 66.03%; cal- culated: 10.76, 22.01 and 65.37% respectively}. Other crystal structures with isolated hexaiodobis- muthate(IIl) anions are not known; only two struc- tures with hexachiorobismuthate(Ill) anions have been published: Cs2NalBiCl61 (Morss & Robinson, 1972)