Bonding in clusters

The examples should not give the misleading impression that bonding in clusters is a clear and simple matter. Next to many examples for which the Wade mles work well, they do not do so in many other cases, or additional assumptions have to be made. 

T. Hughbanks, Bonding in clusters and condesed cluster compounds that extend in one, two and three dimensions. Prog. Solid State Chem. 19 (1990) 329. 

Weinhold F (1997) Nature of H-bonding in clusters, liquids, and enzymes an ab initio, natural bond orbital perspective. J Mol Struct Theochem 398-399 181-197... 

In all the above examples, the carbonyl group donates two electrons to the metal cluster unit. Four-electron donation by the carbonyl group has recently been observed although this appears to be a much less frequent mode of bonding in cluster systems, it has often been invoked to explain the properties of absorbed carbon monoxide on a metal surface. 

Aromaticity/antiaromaticity in cluster systems has certain peculiarities when compared with organic compounds. The striking feature of chemical bonding in cluster systems is the multifold nature of aromaticity, antiaromaticity, and conflicting aromaticity [3-10]. Double aromaticity (the simultaneous presence of [Pg.439]

M. Abu samha, K. J. Borve, J. Harnes, and H. Bergersen, What can Cls photoelectron spectroscopy tell about structure and bonding in clusters of methanol and methyl chloride. J. Phys. Chem. A 111, 8903 8909 (2007). 

The 18-electron rule generally governs the bonding in clusters with up to five metal atoms. The cluster core shape, i.e., the number of metal-metal bonds, can be deduced from the number of electrons provided by the metal... 

Reactions affecting single metal-metal bonds From the knowledge of metal - metal bond reactivity (15) several reaction types which are common for dinuclear complexes can be expected to occur for single metal-metal bonds in clusters. Some of these, such as nucleophilic opening (cf. Section... 

Saba Mattar came to the University of New Brunswick in 1986. His research program is split between experimental and theoretical studies of the electronic structures and bonding in clusters and organometallic intermediates. Several experimental techniques are used to study matrix-isolated transient species, and the results are interpreted with the assistance of multireference Cl calculations.148 He also uses local density functional methods.149... 

The occurrence of weak Au - Au interactions of this type gives rise to the possibility of alternative descriptions of the bonding in clusters... 

Just the atoms in vertexes of first type bonds take part in forming bridge like intermolecular bonds in clusters on base of C2s-... 

This technique is not a direct structural probe, but has been used as an experimental method to augment theoretical calculations on the bonding in cluster systems, including a number of alkyne-substituted complexes (389-391). The basis of the technique is that photons in the vacuum ultraviolet region of the spectrum, whose energy is about 10 eV, interact with molecules in the gas phase to cause either promotion of electrons from one bound state to another or their ejection as free electrons. Photoelectron spectroscopy is only concerned with processes that liberate electrons, either by direct ionization [Eq. (15)],... 

A theory which shows greater applicability to bonding in cluster compounds is the Polyhedral Skeletal Electron Pair Theory (PSEPT) which allows the probable structure to be deduced from the total number of skeletal bond pairs (400). Molecular orbital calculations show that a closed polyhedron with n vertex atoms is held together by a total of (n + 1) skeletal bond pairs. A nido polyhedron, with one vertex vacant, is held together by (n + 2) skeletal bond pairs, and an arachno polyhedron, with two vacant vertices, by (n + 3) skeletal bond pairs. Further, more open structures are obtainable by adding additional pairs of electrons. This discussion of these polyhedral shapes is normally confined to metal atoms, but it is possible to consider an alkyne, RC=CR, either as an external ligand or as a source of two skeletal CR units. So that, for example, the cluster skeleton in the complex Co4(CO)10(RCCR), shown in Fig. 16, may be considered as a nido trigonal bipyramid (a butterfly cluster) with a coordinated alkyne or as a closo octahedron with two carbon atoms in the core. 

Edison, A. E., Weinhold, R, and Markley, J. L., Theoretical studies of protium/deuterium fractionation factors and cooperative hydrogen bonding in clusters, J. Am. Chem. Soc. 117, 9619-9624(1995). 

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