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, R3m, a = 1020.62(5), c = 2035.3(2) pm, Vm = 61.430(8) cm3mol−1) was refined to R = 0.049, Rw = 0.031. From hydrochloric acid solutions of ReCl3 containing me4NCl, the hydrete ReCl3 · 5/3 H2O is salted out: hexagonal, P62c, a = 944.89(3), c = 1470.07(9) pm, Vm = 114.09(1) cm3 mol−1. The crystal structure (R = 0.079, Rw = 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.