Groups and Cluster Compounds

R. J. Gillespie, Ring, cage, and cluster compounds of the main group elements. Chem. Soc. Rev. 1979, 315. 

Naturally, the ideal source of starting materials for homoleptic metal isocyanide compounds is via metal carbonyl complexes, but previously only with the two carbonyls Ni(CO)4 (24) and Co2(CO)g (25) has direct substitution of all carbonyl groups been effected. Recently, however, remarkable discoveries by Coville and co-workers (26-31) on the transition-metal-catalyzed substitution of carbonyl groups in monomeric and cluster compounds have shown that Fe(CNR)s, Mo(CNR)6, and Ir4(CO)5(CNR)7 (32) can be prepared in high yield by stepwise substitution from the parent carbonyl. 

In this section, we introduce the first group of cluster compounds of the heavier -block metals in which the external ligands are halides. Octahedral Mg frameworks are present in most of these clusters, but, in contrast to similar group 5 and 6 species (Sections 23.6 and 23.7), most zirconium clusters are stabihzed by an interstitial atom, e.g. Be, B, C or N. 

The discussion presented above has demonstrated that non-bonding orbitals play an important role in determining the stereochemistries and closed shell requirements of both co-ordination and cluster compounds. In group theoretical terms, whenever there are an odd number of irreducible representations, a non-bonding orbital is generated which is either localised exclusively on the central atom, or the peripheral atoms and has nodal characteristics which lead to a zero or minimal overlap with the remaining atoms in the structure. 

A. Schnepf (2007) Chem. Soc. Rev., vol. 36, p. 745 - Metalloid group 14 cluster compounds An introductirm and perspectives to this novel group of cluster compounds. ... 

PPha, pyridine) organic groups (olefines, aromatic derivatives) and also form other derivatives, e.g. halides, hydrides, sulphides, metal cluster compounds Compounds containing clusters of metal atoms linked together by covalent (or co-ordinate) bands, metaldehyde, (C2H40) ( = 4 or 6). A solid crystalline substance, sublimes without melting at I12 1I5" C stable when pure it is readily formed when elhanal is left in the presence of a catalyst at low temperatures, but has unpredictable stability and will revert to the monomer, ft is used for slug control and as a fuel. 

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