Frustrated Lewis pairs (FLP), i. e. the combination of a Lewis acid (LA) and a Lewis base (LB) that cannot fulfill their natural propensity to form dative adducts, are assuming a growing importance mainly due to their capability of activating small molecules such as H2, CO2 and unsaturated substrates. It is believed that LA and LB must closely approach each other forming an encounter complex, having the empty orbital of LA pointing towards the lone pair of electrons of LB, in order to contemporary exploit their potential as electron donor and acceptor. Despite this, very little experimental evidence is available about the tendency of LA and LB to associate and their relative orientation in solution.In this contribution, we report the results of an in-depth NMR study which provides unprecedented evidence for the tendency of intermolecular frustrated PR3/B(C6F5)3 pairs (R=CMe3, 2,4,6-Me-C6H2) to associate in toluene and benzene, quantified by diffusion NMR experiments.1 The results of 19F,1H HOESY experiments, carried in combination with DFT calculations, are also illustrated; they indicate that there is not any preferred approaching orientation between LA and LB.1 Rocchigiani, L. et al, J. Am. Chem. Soc. 2014  , 136, 112.

Disclosing the tendency to associate and relative orientation of frustrated PR?3?/B(C?6?F?5?)?3? pairs by diffusion and HOESY NMR

248th National Meeting (2014)

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