Establishing the Role of Triflate Anions in H2 Activation by a Cationic Triorganotin(IV) Lewis Acid

Cationic Lewis acids (LAs) are gaining interest as targets for frustrated Lewis pair (FLP)-mediated catalysis. Unlike neutral boranes, which are the most prevalent LAs for FLP hydrogenations, the Lewis acidity of cations can be tuned through modulation of the counteranion; however, detailed studies on such anion effects are currently lacking in the literature. Herein, we present experimental and computational studies which probe the mechanism of H-2 activation using iPr(3)SnOTf (1-OTf) in conjunction with a coordinating (quinuclidine; qui) and non-coordinating (2,4,6-collidine; col) base and compare its reactivity with {iPr,Sn.base}{Al[OC(CF3)(3)](4)} (base = qui/col) systems which lack a coordinating anion to investigate the active species responsible for H-2 activation and hence resolve any mechanistic roles for OTf- in the iPr(3)SnOTf-mediated pathway.