Shannon MCLAUGHLIN1, Ma?gorzata SWAD?BA-KWA?NY1, John HOLBREY1, Leila MOURA1, Nimal GUNARATNE1, Nancy ARTIOLI1, Lucy BROWN1, Anne MCGROGAN1
1QUILL Research Centre, Queen's University Belfast, Belfast, United Kingdom
Frustrated Lewis pairs (FLPs) are compounds or mixtures containing a Lewis acid and a Lewis base that cannot combine to form a classical adduct due to steric hindrance.1-3 The proximity of these free Lewis acidic and Lewis basic sites gives rise to interesting reactivity, including transition-metal-free hydrogen activation.4 Previous studies by our group have shown enhanced encounter complexes formation in ionic liquids. In previous work, the presence of a weakly-associated encounter complex in the model FLP solution: tris-tert-butylphosphine (P(tBu)3) and tris(pentafluorophenyl)borane B(C6F5)3 in benzene, was confirmed via P...B correlation analysis from neutron scattering data and Empirical Potential Structure Refinement (EPSR).5 The low diffusivity characteristics of ionic liquids is suggested to enhance high populations of encounter complex. The FLP in the ionic liquid solution retained its ability to split hydrogen.
In this work, a range of FLP/IL solutions in ionic liquids were investigated for their ability to split hydrogen. Furthermore, Lewis acidic ionic liquids were with Lewis basic ligands on the boron centre were studied as neat IL-FLP systems. Structure-property relationships have been developed for the ability to split hydrogen by these systems. Finally, active FLP/IL solutions have been tested for their ability to hydrogenate model substrates.
References:
1. D. Stephan, Journal of the American Chemical Society, 2015, 137, 10018-10032.
2. D. Stephan and G. Erker, Angewandte Chemie International Edition, 2015, 54, 6400-6441.
3. D. Stephan, Accounts of Chemical Research, 2014, 48, 306-316.
4. G. Welch, R. San Juan, J. Masuda and D. Stephan, Science, 2006, 314, 1124-1126.
5. L. Brown, J. Hogg, M. Gilmore, L. Moura, S. Imberti, S. Gärtner, H. Gunaratne, R. O’Donnell, N. Artioli, J. Holbrey and M. Swad?ba-Kwa?ny, Chemical Communications, 2018, 54, 8689-8692.
Keywords:
Frustrated Lewis Pairs
Hydrogen activation
Hydrogenation