Metal-coordinated bridging ligands assemblies

The bis(dithiolate) ligand (63) has been prepared from 2,3-dimercaptobenzoic acid and employed in the preparation of a dinuclear, air-stable titanocene complex.90 o-Xylyl spacers were also employed. Donors such as (64) are capable of acting as either a mononucleating or a bridging ligand, depending on the stereoelectronic coordination preferences of the metal ion in dictating the course of the assembly process.91... 

There exist a vast number of discrete, polymetallic coordination clusters both of the metal-metal bonded type and linked by a tremendous variety of bridging ligands, notably carboxylates. Such compounds are not coordination polymers but oligomers and hence can be more soluble, more well-defined and easier to characterise than coordination polymers, for which they can serve as useful model systems. We will discuss discrete, self-assembled complexes of semi-protected metal ions that act as hosts in solution or as 3D capsules in the next chapter and we will not cover these systems in detail here except to note in passing a couple of examples that are of particular interest. One particularly prominent cluster is Muij-acetate, the mixed-valence compound... 

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