A morphotropic series of the cluster complexes [Ln(DMF)8][Re6Q7Br7] (Q = S, Se): Synthesis, structure, and thermal transformations

Abstract

The reactions of the octahedral anionic complexes [Re6Q7Br7]3− (Q = S, Se) with lanthanide bromides in DMF were studied. The reactions gave a series of compounds [Ln(DMF)8][Re6Q7Br7] (Q = S, Se) containing [Ln(DMF)8]3+ complex cations. The compounds were studied by single-crystal and powder X-ray diffraction and thermal analyses. The crystal structures of [Ln(DMF)8][Re6S7Br7] with Ln = La (I), Ce (II), Nd (III), Eu (IV), and Lu (V) and [Ln(DMF)8][Re6Se7Br7] with Ln = La (VI), Ce (VII), Pr (VIII), and Lu (IX) were determined. It was found that [Ln(DMF)8][Re6Q7Br7] (Q = S, Se) can be divided into three structural groups: I, II, and VI (type A), VII (type B), and III–V, VIII, IX (type C). The complex [Pr(DMF)8][Re6Se7Br7] was found to crystallize in two polymorphous modifications with type B and C structures. Presumably, the morphotropic transitions in the [Ln(DMF)8][Re6Q7Br7] series (Q = S, Se) are mainly related to the change in the configuration of the [Ln(DMF)8]3+ cations, resulting in a change in the packing motif of large complex ions in the crystals. The compounds [Ln(DMF)8][Re6Se7Br7] decompose according to a stepwise pattern, which suggests an intermediate formation of the complexes [Ln(DMF)6][Re6Se7Br7] (this was proved for Ln = Yb, Lu) with subsequent more extensive transformations, which affect also the cluster anion.