Chalcogen-metal clusters

The chalcogen-capped clusters M M2Co(/(3-S)(CO)s()/ -CsH5) (M M2 = MoEc, MoRu, WFe) and MoFeCo(/r ,-Se)(CO)H()) -CsH3) underw ent a one-electron, quasi-reversible reduction. Addition of an electron proceeded more readily for the clusters w ith the lighter metals and for the selenium capped cluster relative to its sulfur analogue. 

Application to the Controlled Synthesis of Chalcogen-Metal Complexes and Clusters... 

Most of the chalcogenide studies have involved binary, ternary, and pseudo ternary metal clusters. The ternary Chevrel-phases can be represented by MxMo6X8 (M = transition metal, X = chalcogen atom), where the transition metal fills the cavities in the Mo6X8 crystal structure. The pseudo-ternary (or pseudo-binary) Chevrel-phase clusters can be represented by MxMo6 xX8, where the Mo atoms are substituted by transition metal atoms.185 The crystal structure of ternary and pseudo ternary Chevrel phases are shown in Fig. 4. The carbonyl-chalcogenide clusters189 192 will be discussed in the next section. 

Dimensionality reduction in solids (Lee Holm, 1990) has received some attention. Three-dimensional metal cluster solids of the kind [MgQ8]X3 (M = Re, Mo Q = chalcogen X = halogen) can be rendered into two-, one- and zero-dimensional phases sequentially by the incorporation of AX type halides (e.g. A = Tl). The stepwise... 

It should be kept in mind that it is often difficult to ascertain what the active catalyst is. There are, in fact, very few proven catalytic mechanisms where the structure of the actual catalyst is known with certainty. There are, to the author s knowledge, few, and possibly no, proven useful homogeneous catalytic processes that involve metal dimers in the catalytic cycle. In an excellent review on cluster catalysis, Muetterties lists the following processes as metal-cluster-catalyzed reactions (see Table 2). This review also lists the important classes of metalloenzyme clusters however, these compounds do not normally involve metal-metal bonds per se but are usually bridged by chalcogens, such as sulfur or oxygen donors. 

Within this context, the present article concentrates on transition metal cluster complexes of cobalt, iron and manganese with mixed chalcogen/carbonyl ligand spheres obtained by reaction of simple binary metal carbonyls with alkali-metal sulfides, alkali-metal thiolates or transition-metal thiolate complexes and their selenium or tellurium counterparts. 

The ability of PE spectroscopy to interrogate the whole range of valence orbitals of a molecular system has proved invaluable in investigating the electronic structure of metal-metal multiple bonds and small metal clusters. In the organometallic field, most attention has been focused on metal carbonyl dimers and small clusters, and their derivatives, on account of the high stability and volatility of these species. Metal chalcogen clusters of stoichiometry M4CP4E4 (E = O, S, Se) have also proved viable and fruitful candidates for PE spectroscopy. ... 

The use of silylated chalcogen reagents in the synthesis of chalcogen-bridged metal clusters has produced a remarkable number of complexes with a variety of structural types. The nuclearities and structures of these complexes can be highly dependent on the reaction conditions, the steric demands of the ancillary and/or chalcogenolate ligands, as well as the ratio M E. Complexes... 

Several chalcogen-bridged clusters of the group 12 metals (Zn, Cd, Hg) have been synthesized utilizing silylated reagents. Mostly, the structures of these complexes are based on adamantane-like cages, and are similar to II-VI clusters synthesized by other approaches, as described in... 

Chalcogen Bridged D ansition Metal Clusters with i/ -Cydopentadienyl, /13-Allyl, and CO Ligands... 

The intercalation capacity depends weakly on the chalcogen nature for Mo Xg compounds with octahedral metal-clusters and Lig. Mo Sg/2/, Lig. gMogSeg,Lig. gMo TCg intercalates have been obtained. 

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