Frustrated Lewis pairs: Reactions with dihydrogen and other “small molecules”

Frustrated Lewis pairs, comprised of combinations of sterically encumbered phosphine (or amine) Lewis bases with boron Lewis acids containing the strongly electron withdrawing bulky pentafluorophenyl substituents, show very remarkable reaction behaviour. They are able to cooperatively induce heterolytic splitting of dihydrogen under mild conditions. They cooperatively add to various unsaturated organic compounds, including carbon dioxide. With some substrates competing 1,1-carboboration reactions become important. The latter reaction has methodically been developed into a conceptual alternative to the ubiquitous hydroboration reaction and has been used for the development of a novel way of carbon-carbon bond activation.