Mixed-valent selenidoantimonates(III,V) with transition-metal complexes as counterions: solvothermal syntheses and characterization of [M(dien)2]2Sb4Se9 (M = Mn, Fe), [Co(dien)2]2Sb2Se6, and [Ni(dien)2]2Sb2Se5

Novel selenidoantimonate compounds M(dien)2]2Sb4Se9 M = Mn (1), Fe (2)], Co(dien)2]2Sb2Se6 (3), and Ni(dien)2]2Sb2Se5 (4) (dien = diethylenetriamine) were solvothermally synthesized and characterized. The unique features of compounds 1-3 are the mixed-valent anionic structures constructed by the Sb(III)Se3 trigonal pyramid and Sb(V)Se4 tetrahedron. Three Sb(III)Se3 pyramids share common corners, forming a heterocyclic Sb3Se6 moiety, and the Sb3Se6 moieties are further connected with Sb(V)Se4 tetrahedra to form the novel one-dimensional Sb4Se9(4-)]n anionic chain in 1 and 2. The discrete Sb2Se6]4- anion in 3 is formed by an Sb(III)Se3 trigonal pyramid and an Sb(V)Se4 tetrahedron sharing a common corner. The Sb2Se5]4- anion in 4 is composed of two Sb(III)Se3 trigonal pyramids connected in the same manner as the Sb2Se6]4- anion. The mixed-valent Sb4Se9(4-)]n and Sb2Se6]4- anions were not observed before. The synthesis and solid-state structural studies of the title compounds show that the transition-metal complexes exhibit different structure-directing effects on the formation of selenidoantimonates in dien. Extensive N-H...Se hydrogen bonds are observed between cations and anions in compounds 1-4, resulting in three-dimensional network structures. Optical and thermal properties of the compounds are reported.