Rhenium hexanuclear clusters

J.-C.P. Gabriel, K. Boubekeur, S. Uriel, O. Batail, Chemistry of hexanuclear rhenium chalcogenide clusters. Chem. Rev. 101 (2001) 2037. 

Penta- and hexanuclear clusters of the metals osmium and ruthenium coordinate with the same r ri ri - binding mode as the trinuclear clusters to CgQ. Such complexes are known for the clusters OsjC [75,76], RU5C [77-79], RugC [78], PtRu5C [77] and Rhg [80], In this collection of metal clusters rhenium plays a special role, because it forms a new fullerene-metal sandwich complex, where two C50 are bound to one cluster. 

It seems natural to suppose that the tetragonal distortion of the tri-anion results from the Jahn-Teller effect. In order to study the problem more thoroughly we undertook recently the DFT calculations of this cluster as well as of several other hexanuclear rhenium chalcohalide clusters. The technical details of these calculations can be found in the original publication [8]. Here we only want to note that the introduction of relativistic corrections for Re atoms is crucial for the correct reproduction of the geometry of clusters. In our calculations, this was done by the zero order regular approximation (ZORA) Hamiltonian [9] within ADF 2000.02 package [10]. 

Hexanuclear Clusters Clusters of six molybdenum, niobium, or tantalum atoms have been known for many years, predating the work with rhenium. There two types In the first, an octahedron of six metal atoms is coordinated by eight chloride ligands, one on each face of the octahedron. This is found in molybdenum dichloride, Mo6C112, better formulated as [Mo6C18]C14. Each Mo (II) atom can use its four electrons to form four bonds with adjacent molybdenum atoms and can receive dative bonds from the four chloride ligands. 

Hexanuclear chalcohalide Rhenium(III) clusters UV-Vis B3LYP, PBEIPBE, B2PLYP/ LanL2DZ CPCM 100... 

We discuss here two examples of vibronic effects in polynuclear highly symmetrical transition metal clusters. The existence of degenerate and quasi-degenerate molecular orbitals in their energy spectra results in the Jahn-Teller effect or in the vibronic mixing of different electronic states. We show that both quantum-chemical methods and model approaches can provide valuable information about these vibronic effects. In the case of the hexanuclear rhenium tri-anion, the Jahn-Teller effect is responsible for the experimentally observed tetragonal distortion of the cluster. The vibronic model of mixed-valence compounds allows to explain the nature of a transient in the photo-catalytic reaction of the decatungstate cluster. 

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