Metal-carbonyl clusters specific metals

These observations on the structurally simple carbides of the early transition metals show how the strength of binding of core carbon atoms in molecular metal carbonyl clusters can in principle be estimated by comparison with metal carbides for which structural and theoretical data are available, and leads us to hope that examination of the wider body of transition metal carbides will provide relationships between the length and strength of bonds between metal atoms and octahe-drally coordinated carbon atoms that can be applied to specific molecular metal carbonyl clusters containing core carbon atoms. 

Braga and Grepioni have undertaken a series of analyses of the crystal structures of metal carbonyl clusters, 7t-arene complexes, mixed carbonyl n-arene complexes and some substituted derivatives [170]. Their analyses are based on examination of the packing details and motifs in the crystal structures, recognition of specific interactions, calculation of the packing potential energy for the crystal and consideration of contributions to the lattice volume. Their objective, to investigate the interplay between molecular structure and crystal structure, is very similar to the perspective in this article. 

A number of review articles have described the applications of multinuclear NMR methods for studying structures and internal rearrangements of metal clusters. The more specific cluster types covered were transition metal carbonyl clusters/ chiral clusters/ and mixed metal clusters containing carbyne or ketenylidene bridges. ... 

A topical review of the potential of heterogeneous metal carbonyl clusters has been published. The author describes the ideas behind the specific engineering of catalytic surfaces using metal carbonyl clusters. The utilisation of metal carbonyl clusters in homogeneous catalysis has been thoroughly reviewed (inc 410 references) by Suss-Fink and Meister. ... 

As befits current interest, the largest number of reviews centre on metal carbonyl cluster compounds. General topics covered included electron transfer reactions, ligand and cluster transformations, and the chemistry of metal clusters containing nitrosyl and nitrido ligands.More specific topics reviewed include sulphi do-osmium carbonyl cluster compounds,and homonuclear platinum clusters.The preparations of [Nb(C0)6] [M2(CO)io(m-H)]" (M = Cr or W), Mn2(C0)aX2 and Re C0)sX (X = Cl, Br or I) are described in Volume 23 of Inorganic Syntheses. ... 

Vibrational spectroscopy (particularly infrared) has found wide application in the characterisation of supported metal carbonyl clusters. Such studies have been facilitated by the advent of high-sensitivity Fourier transform instrumentation. However, the information provided should be used with caution — the behaviour of carbonyl stretching vibrations need not necessarily correlate in any definite or specific manner with the presence or absence of metal-metal bonding in a supported organometallic carbonyl species. 

High-nuclearity carbonyl clusters, 30 123-222, see also specific metal and clusters decrease in cluster nuclearity, 30 152 interstitialhydrido, NMR data, 30 168 large hydrido clusters, structure, 30 168-172... 

The reaction expressed in Eq. (88) is the reverse of the hydrogen addition [Eq. (84)] and constitutes one of the few demonstrated cases of reductive elimination of H2 from an intact cluster. The tetranuclear clusters that have been studied appear to fragment consistently in the presence of CO, to produce a metal carbonyl trimer and a monomeric fragment in highly specific fashions. 

This article is concerned with one specific aspect of cluster organometallic chemistry, and describes the synthesis, characterization, structure, and reactivity of transition metal clusters containing alkyne, or alkyne-derived ligands. Alkynes display a diverse reactivity in their reactions with carbonyl clusters, and exhibit a wider range of coordination modes than any other simple, unsaturated molecule. It is this compelling diversity that has prompted the authors to undertake this review. 

An important frontier in cluster chemistry is the effect of electron count on reactivity. Are clusters merely passive electron reservoirs or does the number of electrons have a critical influence on reactions other than electron transfer Conversely, how does the number of metal atoms, the relative ratio of heterometals, and the specific ligand set relate to the ability of clusters to enter into redox reactions These questions are of fundamental interest, but the answers also may have practical consequences, for example, in the development of metal nanoparticles or colloids to act as electrocatalysts. In a final group of articles Longoni and coworkers review the ability of homoleptic carbonyl clusters to act as electron-sinks , Zanello and Fab-rizi de Biani examine the effect of heterometallic interactions on cluster redox aptitude, and Ignaczak and Gomes report on modelling of electrode interactions with metal clusters. 

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