Design Bridging the Dirhodium Core

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. 

A key question was whether or not the bridged dimer would effectively catalyze the C-H insertion reaction. We were pleased to observe that complex 55 is in fact an efficient catalyst (1610 turnovers) for the cyclization of 47 to 48 (Eq. 2). 

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