Multicentered bonding and quasi-aromaticity in metal-chalcogenide cluster chemistry

On the basis of the localized molecular orbital (LMO) theory, the bonding schemes for the following types of cluster compounds are briefly reviewed in this paper; the linear Et₄N]Cl₂FeS₂MoS₂Cu(PPh₃)₂] cluster, triangular trinuclear M ₃(₃–X)(–Y ₃]⁴⁺ (M = Mo, W;X = O, S;Y = O, S, Se) clusters, triangulated polyhedral clusters: closo-boranes B _n H _n ^2–, octahedral Co₆(CO)₁₄]^4–, Ni₂Co₄(CO)₁₄]^2– and Co₆(₃ –X ₈ ·L ₆ ⁿ⁺ (X = S, Se;L = PPh₃, PEt₃, CO;n = 0,1) as well as quasi-aromatic cluster ligands in cubane-type Mo₃S₄ ·ML _n ^{(4 +q) +} (M = Mo, W, Fe, Ni, Cu, Sn, Sb;L = Ligand and sandwich-type Mo₃S₄ ·M · S₄Mo₃]⁸⁺ (M = Mo, Sn, Hg). We put emphasis upon the characteristics of multicentered bonding in these cluster molecules, and, especially, point out existence of a novel species of quasi-aromatic cluster compounds.