Trinuclear dusters

Monomeric complexes of W1 1 such as the halides, the oxyhalides and their derivatives have been known for quite some time. In most cases these are six-coordinate, but higher coordination numbers are also known. During the last two decades, new structural types have been reported. Of these, the most interesting are the dinuclear complexes containing W=W double bonds and the trinuclear dusters containing W—W single bonds. 

During the past several years it has been shown that both molybdenum and tungsten in oxidation states of +4 or thereabouts, have marked predilection to form trinuclear duster species. For the tungsten cluster spedes, there are three different structural types with respect to the ligand arrangements (Figure 24 a, b, c) which are based on an equilateral triangle of M—M bonded atoms. Structure (a) contains th [W3(j 3-X)(ju-Y)3] nucleus, where X = 0, Cl,... 

Trinuclear dusters are nearly always triangular, often heteronuclear, and very numerous. The M3(CO)i2 clusters of Fe, Ru, and Os have been much studied and can be used to illustrate some typical cluster chemistry. The Os3(CO)i2 cluster with the structure (16-XIII), where CO groups are denoted simply by lines, are electronically precise, namely, they have exactly the right number of electrons to provide each metal atom with an 18-electron, closed shell configuration. In such systems there is a total of 48 electrons, and each M—M bond is of order 1. As... 

Figure 16-22 Four of the most important types of trinuclear duster structures. Solid circles are metal atoms and open circles nonmetal (ligand) atoms.

ResBrg is similar to Re3Cl9 but the iodide, which is a black solid and is similarly trinuclear, differs in that it is thermally less stable and only 2 Re atoms in each duster are linked to adjacent clusters, thereby forming infinite chains of trimeric units rather than planar networks. 

A stepwise metallation strategy was also used to successfully form a trinuclear heterometallic duster featuring Fe-Mn interactions. The trigonal FejMn " core in ( L)Fe2Mn(THF) was assembled by heating the diiron intermediate ( LH2)Fe2 and 0.5 equiv. Mnj(N(SiMe3)2)4 at 75 °C in THF (Figure 8.34) [223]. The solid-state structure showed Fe-Mn distances of 2.7247(5) and 2.7485(5) A... 

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