The resting-state form of catalyst 1g was investigated by employing diffusion-ordered NMR spectroscopy (DOSY) to measure its diffusion constant under catalytic reaction conditions as a means of estimating its molecular weight (see Supplementary Materials, Section 8.2). The trifluoromethyl groups on 1g provided a sensitive handle for 19 F NMR measurements at concentrations of 1g approximating the catalytic conditions (10 mM, 5% Et2O/toluene-d8, -70 °C).