CLUSTERS inorganic compounds

Metal-metal (M-M) bonds, first noted in the early sixties, occur in several thousand transition-metal compounds [1]. Complex technetium compounds and compounds with M-M bonds (clusters) have been studied more extensively than many other classes of inorganic compounds. Increasing interest in technetium compounds is due to the practical uses of the "mTc isotope, which ranks first among radioactive isotopes used in nuclear medicine diagnostics [2-4]. On the other hand, technetium clusters are an interesting object for theoretical studies, because until recently, they were the only compounds in which the presence of these anomalous chemical bonds was thought possible. 

Harada A (1994) Stereochemistry of Organometallic and Inorganic Compounds, Vol 5, Chains, Clusters, Inclusion Compounds, Paramagnetic Labels, and Organic Rings. Zanello P (ed), Elsevier, Amsterdam, p 409... 

There are several interesting families of inorganic mixed-valence compounds that we have not discussed here (see Yvon, 1979 McCarley, 1982). For example, there are metal-cluster compounds such as the Chevrel phases, M,jMo6X8(X = S or Se) and condensed metal-cluster chain compounds such as TlMojScj, TijTe, NaMo O and M PtjO. TTF halides and TTF-TCNQ complexes (Section 1.9) constitute molecular mixed-valent systems in which the mixed valency is associated with an entire molecule the charge on TTF in such compounds is nonintegral. The structure of TTF-Br(, 79 and... 

Polynuclear inorganic compounds exist in a bewildering array of structural types, such as ionic solids, molecular polymers, extended assemblies of oxounions both of metals and nonmeinis, nonmetal chains and rings, bridged melui complexes, and homo- and hetero-nuclcar clusters. This section treats primarily the nomenclature of bridged metal complexes and homo- and hetero-nuclear dusters. 

Enzymes are large protein molecules (apoenzymes), which act as catalysts for almost all the chemical reactions that occur in living organisms. The structures of a number of enzymes contains groups of metal ions, known as metal clusters, coordinated to the peptide chain. These enzymes are often referred to as metalloenzymes. Many enzymes require the presence of organic compounds (co-enzymes) and/or metal ions and inorganic compounds (co-factors) in order to function. These composite active enzyme systems are known as holoenzymes. 

This technique has been used extensively as an experimental comparison for one or other of the types of theoretical molecular orbital calculations for organic and some nonmetallic inorganic compounds. However, for transition metal complexes and cluster compounds, their lower volatility presents some difficulties, and for the photoelectron spectra of the cluster alkyne complexes that have been recorded a heated inlet probe has been used to overcome this problem. 

These clays have been hybridized with diverse structural types of components such as nanoparticles, clusters, complex compounds, polymers, molecules, and ions. Their potential apphcations are found in many fields as inorganic catalysts, adsorbents, ceramics, coatings, and even drug delivery carriers. Various preparation methods have been developed such as pillaring, intercalation, and delamination techniques. The representative examples include organic-clay hybrids," metal oxide-pillared clays, " and bioclay hybrids. ... 

Such clusters of FeOe octahedra also exist in other inorganic compounds. For instance they exist in ilvaite (CaFe TFe 2Si20700H) where silicate layers replace phosphate anions and FeOs octahedra form ribbons. It is interesting to note that such a material is active and selective for the reaction although to a lesser extent than the previous hydroxyphosphates [24]. The lower catalytic behaviour may be due to the presence of Ca " cations in the structure and/or to the silicate counter anion whose basicity in the sense of Pearson is different from that of the phosphate anion and/or the infinite size of Fe06 octahedra clusters. 

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