Electronic structures of [M 3(μ 3-X)(μ 2-S 2) 3] 4+(M = Mo, Ti) cluster compounds and the effects of the μ 3-X cap to the self-assembly in cluster synthesis

Abstract

The electronic structures and bonding in one class of trinuclear transition-metal cluster compounds having the cores [Ti 3(μ 3-O)(μ 2-S 2) 3] 4+ ( 1), [Mo 3(μ 3-S 2) 3] 4+ ( 2) and [MO 3S 4] 4+ ( 3) are discussed in terms of the results of molecular orbital (MO) calculations using the CNDO/ 2-LMO method. There are certain strong bonding interactions between the metal atoms in clusters 2 and 3, but no significant metal-metal bonding is found in cluster 1. The existence of one four-centred bond consisting of three skeletal Mo atoms and the μ 3 cap in cluster 2 is of particular importance for shedding light on the nature of the self-assembly syntheses. From the analysis of the localized MO (LMO) we conclude that the μ 3-O cap and the μ 3-S cap have an important effect on the self-assembly of the trinuclear clusters.