Electronic configurations cluster complexes

Slovokhotov, Yu.L. and Struchkov, Yu.T (1984) X-ray crystal structure of a distorted tetrahedral cluster in the salt [(Ph P)4Au4N] BF4 . Geometrical indication of stable electronic configurations in post-transition metal complexes and the magic number 18-e in centred gold clusters. Journal of Organometallic Chemistry, 177, 143-146. 

The theoretical treatment of bonding and structure of gold clusters has met with considerable success. For the higher gold dusters, the best predictions are that, for a cluster [AutL, 1]"+ in which the peripheral gold atoms define a closed spherical polyhedron, there will be a closed shell electron configuration when 12x + 6 electrons are present. The structures of complexes... 

Platinum cluster complexes with Pt—Pt bond(s) having various oxidation states are well known, and many exist in low-valent oxidation state, such as a series of [PtsCCOeln and phosphine or isocyanide clusters 1-9). A platinum ion with an odd d electron tends to form a dimeric complex having a Pt—Pt single bond involving the unpaired electrons. Monovalent platinum forms dimeric cluster complexes with a d -d configuration (10-14) and tervalent platinum forms d -d ... 

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). 

Coordination componnds of Os and Os are very rare/ and when detected are often intermediates in redox reaction. Os and Os complexes have d and d electron configurations respectively, and are often associated with organometallic clusters. 

Tricobalt clusters with one triply bridging ligand, isostructural with 65, have been extensively investigated. The carbonyls [Co3(CO)9(/u-E)] (72) (E = S, Se, or PR) have one electron in excess of that required for an 18-electron configuration about each metal. The half-filled orbital is antibonding with respect to the metal triangle (144, 145), and the complexes are easily oxidized (see also, Section IV,B). 

For clusters containing transition metals, there are closely spaced electron orbitals that can assist in electron-redistribution or electron-exchange reactions that involve excited states or slightly varying electron configurations. Stated differently, the LUMO orbitals in transition metal complexes are sufficiently close to HOMO orbitals that they can store electrons at low energy cost. Thus, metal centers on nanoclusters can accelerate reactions that involve electron redistribution. 

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