CLUSTERS coordination compounds

While many compounds of the type X As(ER3)3 (n =0-2 X = any other group, e.g. H, Hal, R etc. R = H, alkyl, aryl E = Ge,263 Sn, 64 Pb265) have been produced, they are mainly of interest to theoreticians and synthesists. They have the expected pyramidal geometry of AsX3 compounds, and their interest to coordination chemists lies in their behaviour as ligands, which is dealt with elsewhere (Chapter 12.2) there is some special interest in cluster coordination compounds involving As—Ge bonding,... 

Development of Coordination Chemistry Since 1930 Coordination Numbers and Geometries Nomenclature of Coordination Compounds Cages and Clusters Isomerism in Coordination Chemistry Ligand Field Theory Reaction Mechanisms... 

Mildvan AS, Grisham CM (1974) The Role of Divalent Cations in the Mechanism of Enzyme Catalyzed Phosphoryl and Nucleotidyl. 20 1-21 Mingos DMP, Hawes JC (1985) Complementary Spherical Electron Density Model. 63 1-63 Mingos DMP, Johnston RL (1987) Theoretical Models of Cluster Bonding. 68 29-87 Mingos DMP, McGrady JE, Rohl AL (1992) Moments of Inertia in Cluster and Coordination Compounds. 79 1-54... 

A review28 describes compounds of the Pt-group metals including halide, oxide, sulfide, coordination compounds, organometallic compounds, and metal cluster compounds. 

Pierce-Smith converter, 16 145 Piezochromic materials, 6 606-614 22 708t coordination compounds and metal cluster compounds, 6 610-611 organic molecules in crystals and polymer films, 6 607-610 organometallic complexes of Cu(II),... 

Fig. 1. Clustering versus partitioning. In cluster analysis, compounds (gray dots) are grouped together based on the calculation of pairwise intermolecular distances in chemical space. By contrast, partitioning methods subdivide chemical space into sections into which compounds fall based on their calculated descriptor coordinates.

Compounds containing niobium or tantalum in negative formal oxidation states -I and -III are mainly metal carbonyl anions. Although these are organometallic derivatives, the report of efficient procedures for the synthesis of [M(CO)6] since the review of Labinger8 merits mention, as it can be anticipated that these highly reduced and reactive species will be important precursors of a large variety of new coordination compounds and metal clusters. 

Hiickel method ( Section 4.4). In the hands of Hoffmann, to whom we owe the EHM in its current form [112], extended Hiickel calculations have given powerful insight into the structures of these compounds. Wide-ranging corroboration of this assertion is seen in Hoffmann s Nobel lecture [100]. Some other examples are a polymeric rhenium compound [113], manganese clusters [114], and iridium [115] and nickel [116] coordination compounds. 

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. 

The coordination compounds of the alkaline-earth metals are becoming increasingly important to many branches of chemistry and biology. A considerable degree of structural diversity exists in these compounds, and monomers up to nonametallic clusters and polymeric species are known. 

Photochemical behaviour of coordination compounds described in previous chapters results mainly from electronic interactions between the central metal atom or ion and ligands in the hrst coordination sphere. An increased size of molecular systems to clusters and nanosized crystals expands the possibility of photoinduced electron transfer between the discrete electronic states to excitation within bands. Furthermore, interactions of nanoparticles with molecules yield unique materials, combining structural versatility of molecular species with collective properties of solids. 

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