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Density functional theory using the B3LYP and BP86 functional is employed to study the divanadocene carbonyls [Cp.sub.2][V.sub.2][(CO).sub.n]. Results reveal extremely short vanadium distance predicted for the singlet structure of [Cp.sub.2][V.sub.2](CO).

The effect of unsaturation on the structure and bonding in the unsaturated chromium carbonyl nitrosyls is examined to compare with the isoelectronic homoleptic manganese carbonyl derivatives by using the density functional theory method. It is observed that there are significant shifts in the relative energies of various structural types of metal carbonyl nitrosyls particularly for unsaturated molecules.

A density functional theory is used to investigate the binuclear vanadium carbonyls [V.sub.2][(CO).sub.n] due to the mononuclear vanadium carbonyl V[(CO).sub.6] failure to satisfy the 18-electron rule. It is observed that the [V.sub.2][(CO).sub.10] isomer produced in the photolysis of gas-phase V[(CO).sub.6] agree with the theoretical V(CO) frequencies and the laboratory bridging V(CO) frequency assigned to [V.sub.2][(CO).sub.12] arises from the lowest-lying triplet isomer of [V.sub.2][(CO).sub.11].

The binuclear cyclopentadienyliron carbonyls Cp2Fe2(CO)(sub n) (n = 4, 3, 2,1; Cp = eta(super 5).C5H5) are studied by density functional theory using the B3LYP and BP86 methods. For the unsaturated Cp2Fe2(CO)3, the known triplet isomer Cp2Fe2(mu-CO)3 with an Fe=Fe double bond similar to the O=O double bond in O2 is found to be the global minimum.

The description of analogies between the symmetries of the bonding molecular orbitals in octahedral cages involving p-orbital delocalization, such as B(sub 6)H(sub 6)(super 2-), and those in analogues coinage metal cages involving d-orbital delocalization. The magnetic properties reveal that the copper cages are likely to be most stable among coinage metal cages.

The structural characterization of the highly unsaturated nonacarbonyldivanadium V2(CO)9 is presented. The results supports that metal-metal bonds with an order larger than three are not usually favorable in metal carbonyl chemistry.

Candidates for lowest energy structures of mediums-zed Au(sub n), n= 32, 38, 44, 50, and 56, clusters are evaluated using gradient-corrected DFT computations. Results reveal that the space-filling isomers are lower in energy except for two notable cases.

Immense efforts are made to develop various criteria of aromaticity and these criteria are used not only to explain the available experimental observations but also to design novel aromatics. Extending the aromaticity concept from the classical two dimensional annulenes to spherical species opens a new exciting research area with particular emphasis on fullerenes and closo-boranes.

The binuclear cyclopentadienylcobalt carbonyls Cp2Co2(CO)(sub n) (n = 3, 2, 1 and Cp = eta(super 5)-C5H5) are studied by density functional theory using the B3LYP and BP 86 functionals. For Fe2(CO)(sub 9), the well-known Fe2(CO)(sub 6)(mu-CO)(sub 3) isomer is shown to be close in energy to the unknown Fe2(CO)(sub 8)(mu-CO) isomer, with the precise relative energies depending on the basis set used.

Research has been conducted on the anionic mixed rhodium-nickel carbonyl clusters. The relationships between these clusters and such group 13 analogues as polyhedral borane and metallaborane frameworks have been investigated and are discussed.

Research has been conducted on the boron polyhedra. The description of these boron polyhedra has been performed in terms of their local vertex environments different from those found in ideal icosahedra and the results indicate that vertices of the degree other than 5 are defective.

Research has been conducted on the binuclear homoleptic carbonyls. The use of different density functional methods in studying the structure, vibrational frequencies and energetics of these carbonyl compounds is described.

Research has been conducted on the metalloboranes. The extension of the anomalous electron counts in the metalloboranes containing a single transition metal vertex to the dimetalloboranes and trimetalloboranes containing early transition metal vertices with low skeletal electron counts has been investigated.

The cobalt carbonyl Co(sub)2(CO)(sub)5 exhibits a monobridged closed-shell singlet with a 2.17 angstrom cobalt-cobalt bond of the order of four. The Co(sub)2(CO)(sub)8 form possesses a crystal structure of C(sub)2 symmetry. The latter compound shows three energetically low-lying equilibrium structures and the Co-Co stretches exhibit identical vibration patterns.

Research is presented demonstrating the single, double and triple bonds of binuclear homoleptic nickel carbonyls. Central bond distances are predicted and prospects for related dinickel compound synthesis are discussed.

The structures, as well as the titanium-titanium multiple bonding taking place in the several different binuclear cyclopentadienyltitanium carbonyls are discussed. The presence of different number of units and the carbonyl groups in different energy complexes is also demonstrated.