Metal cluster compounds electronic configurations

Wade expanded the 1971 hypothesis to incorporate metal hydrocarbon 7T complexes, electron-rich aromatic ring systems, and aspects of transition metal cluster compounds [a parallel that had previously been noted by Corbett 19) for cationic bismuth clusters]. Rudolph and Pretzer chose to emphasize the redox nature of the closo, nido, and arachno interconversions within a given size framework, and based the attendant opening of the deltahedron after reduction (diagonally downward from left to right in Fig. 1) on first- and second-order Jahn-Teller distortions 115, 123). Rudolph and Pretzer have also successfully utilized the author s approach to predict the most stable configuration of SB9H9 (1-25) 115) and other thiaboranes. 

As used here cluster refers to molecules that contain at least 3 metal atoms and electron configurations suitable for the formation of metal-metal bonds. Molybdenum readily forms strong homoleptic metal-metal bonds (see Homoleptic Compound) and so it is not surprising that molybdenum is readily incorporated into cluster stractures (see Polynuclear Organometallic Cluster Complexes). 

Most metal cluster compounds are prepared by the oligomerization of coordinatively unsaturated species in which the central metal atom has less than the 18-electron rare gas configuration. In forming the metal cluster compound, the central metal atom attains coor-dinative saturation and, in most cases, acquires the... 

Interestingly, compounds of Class A or Class B have 50 cluster valence electrons if the three metal atoms are individually to have 18-electron configurations. Several of the compounds meet this requirement, e.g. (25), (27), (31) (34) or (36). However, compound (23) with 46 clusterValence ... 

For the mononuclear and dinuclear compounds, except V(CO)6, the mnnber of valence electrons per metal atom is 18. The EAN (effective atomic number) of the metal is the number of electrons of the d" configuration added to twice the number of CO groups, one electron being further added in the case of metal-metal bonded dinuclear systems. For trinuclear, tetranuclear, and hexanuclear compoimds (metal-carbonyl clusters), the cluster valence electron counting is 48, 60, and 86, respectively. As the [K(cryptand 2.2.2)] derivative. As the tetraalkylammonium derivative. As the tetrachloroaluminate. 

For simplicity, we assumed that all the compounds are the cluster with Td symmetry or Oh symmetry, where the 3d transition metal atom is located at the center and surrounded by four or six ligand atoms. In the case of EC, it is also assumed that there is no change in the chemical environment by electron capture, but only the atomic number of the central atom decreases by one. The internuclear distance is taken to be same as that of the parent atom and the electron configuration of the parent atom is used. 

Another series of cubic clusters of general composition M9(/.i4-E)6Lg (M = Ni or Pd E = Ge, P, As, Te) incorporates a metal atom in the center of the cube. The bonding in these cluster compounds is also analyzed by means of EH and SCF-MS-Xa calculations. The number of MVE ranges from 130 to 121. Examination of the electronic structures has shown that the cluster compounds are at the interface between molecular and solid state materials. In the cubic clusters, closed-shell electron configurations of stable molecular systems with a significant HOMO-LUMO gap coexist with open-shell electron configurations of solid-state systems with no significant gap between the skeletal frontier orbitals. 

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