Crystal structures of trans-[Re6S8(CN)2L4] complexes, L = pyridine or 4-methylpyridine

International audienceThe structures of three novel octahedral rhenium cluster compounds [Re6S8(CN)(2)(py)(4)]center dot H2O (1), [Re6S8(CN)(2)(4-Mepy)(4)] (2), [Re6S8(CN)(2)(4-Mepy)(4)]center dot 4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) , b = 14.772(1) , c = 9.2122(6) , beta = 119.085(2)A degrees, V = 1761.7(2) (3), d (x) = 3.318 g/cm(3), R = 0.0585 (1); I4(1)/amd space group, a = 16.0018(3) , c = 14.7186(5) , V = 3768.81(16) (3), d (x) = 3.169 g/cm(3), R = 0.0489 (2); P2(1)/c space group, a = 9.0452(4) , b = 15.8065(7) , c = 15.2951(6) , beta = 103.700(2)A degrees, V = 2124.57(16) (3), d (x) = 2.957 g/cm(3), R = 0.0245 (3). Molecular cluster complexes interact via pi-pi stacking affording 3D frameworks in 1 and 2 and chains in 3

Systematic Study of Vibrational Spectra of Octahedral Rhenium Clusters {Re₆S_8-xBr_x}Br_y (x = 0, 1, 2, 3, 4) with Mixed Sulfur/Bromine Inner Ligands

A series of rhenium compounds with the octahedral cluster core {Re6S8-xBrx} (x = 0–4): with molecular and polymeric structure were obtained. In these compounds the cluster core composition varies monotonically, the geometry of the cluster and the rhenium coordination polyhedron are retained unchanged, while the symmetry of the cluster changes. The vibrational spectra (Raman and IR) were recorded and analyzed for compounds with all possible S/Br ratios in the cluster core. The group vibrations of clusters were attributed with the use of DFT calculations of vibrational spectra. It is shown that the set of main characteristic bands is retained in both ionic and polymeric compounds regardless of the composition and the symmetry of the cluster core while the observed vibration frequencies of these bands depend on the S/Br ratio in the cluster core. In particular, the group Re–S stretching vibrations (A1g(S8) and T2g(S8) modes) shifted to higher frequencies with the increase in the number of Br atoms in the cluster. The difference in the connectivity in polymeric compounds leads to an increase in the number of bands in the spectra and to the disappearance of the A1g(Br) modes