Complexes containing three metal atoms

The reaction of an olide complex with a strong base can form a new kind of complex containing two metal atoms and three carborane residues in which the carborane residue at the center has two boron atoms removed (Fig. 19). The central ion is called a canistide ion from the Spanish word for basket. ... 

A new field of coordination chemistry is that of polymetallic cage and cluster complexes [Mm(p-X)xLJz with molecular (i.e. discrete) structure. They contain at least three metal atoms, frequently with bridging ligands X and terminal ligands L. These compounds link the classical complexes (m = 1) and the non-molecular (m - oo) binary and ternary compounds of the metals.1 Molecular polymetallic clusters (with finite radius) also provide a link with the surfaces (infinite radius) of metals and their binary compounds.2"5 Polymetallic complexes are known for almost all metals except the actinides. 

The other two classes of imido complex contain bridging imido ligands between two metal atoms as in [(/u,-NH)(/a-0) Mo-(0)[S2P(0Et)2l2 2], and between three metal atoms as in the iron cluster (37). 

The t)1-BH4 coordination is much less common than the other two coordination modes. Most of the r l complexes are constituted by late transition metals and a large variety of phosphino ligands. Only tetrahedral (1.4/T1.4) and octahedral (1.6) structures have been crystallographically characterised (see Scheme 2). Complexes adopting tetrahedral geometries are d10 and contain three phosphorus atoms coordinated to the metal centre. Although some examples of pentacoordinated complexes are present in the literature, these... 

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