Coordination Induced Atropisomerism in an NHC-Based Rhodium Macrocycle

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.