Coordination Induced Atropisomerism in an NHC-Based Rhodium Macrocycle

Abstract

Reversible interaction with carbon monoxide results in the onset of dynamic atropisomerism at 298 K in an otherwise static NHC-based rhodium pincer complex, [Rh(C^N^C-(CH2)12)(CO)][BArF4] (1, ArF = 3,5-C6H3(CF3)2). The mechanism of this process has been comprehensively interrogated by a combination of variable-temperature NMR spectroscopy, IR spectroscopy, and computational modeling. In addition, a structural analogue of a high-energy symmetrical intermediate species—invoked in the process but not directly observed spectroscopically—has been prepared and characterized in solution and the solid-state.