Catalysts design bridging ligand

Here we have discussed only very few of the many ligands that have been studied. Many variations of substituents at the cyclopentadienyl ligand have been studied, and there are more to come as well as variation in the structure of the bridge, the anions, and the central metal. In summary, the toolbox is quite extensive prediction of properties of new polymers to be made can guide the catalysis research in the design of new catalysts. 

In approaching the design of a chiral catalyst, the first question was whether or not our computational approach would allow prediction of the conformation of the ligands around the Rh-Rh core. Although several hundred tetrakiscarboxylato metal-metal dimers were known [20], there had been no report of a dicarboxylic acid that would bridge two positions on such a dimer [21]. We reasoned that the best chance for success would be with a dicarboxyhc acid that was specifically designed to fit across the 5.4 A gap between the carboxylate Hgands. 

Recently, Ewen et al. have designed C2-, Cj-, and Ci-symmetric catalysts bearing heterocycle-condensed Cp ligands, as illustrated in Scheme 9, which add electronic effects to the stereocontrol. ° The complexes, containing isopropylidene-bridged cyclopentadienyl and cyclopentyl thiophene ligands, show activity... 

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