Rhenium trichloride,ReCl3, and its 5/3-hydrate synthesis,crystal structure,and thermal expansion

Single crystals of ReCl₃ were grown by vacuum sublimation and the crystal structure (trigonal, R3 m, a = 1020.62(5), c = 2035.3(2) pm, V_m = 61.430(8) cm³mol^?1) was refined to R = 0.049, R_w = 0.031. From hydrochloric acid solutions of ReCl₃ containing me₄NCl, the hydrete ReCl₃ · 5/3 H₂O is salted out: hexagonal, P6 2_c, a = 944.89(3), c = 1470.07(9) pm, V_m = 114.09(1) cm³ mol^?1. The crystal structure (R = 0.079, R_w = 0.051) contains hexagonally closest-packed Re₃Cl₉(H₂O)₃] molecules held loosely together by two molecules of crystal water positioned between the clusters in the 00.1] direction thereby forming chains that are shifted against each other by 1/2c. Thermal expansion of ReCl₃, ReCl₃. 5/3 H₂O and RbReCl₄ has been recorded and is discussed in connection with the crystal structures.