The heterolytic cleavage of H2 via frustrated Lewis pairs (FLP's) represents a new concept in sustainable chemistry that has the potential of replacing expensive, less abundant and toxic precious metals. One of the major disadvantages, however, is that the currently available FLP's capable of cleaving H2 are largely limited to highly fluorinated boranes such as B(C6F5)3 and RB(C6F5)2 and synthetic procedures to these expensive Lewis acids involve hazardous or explosive materials (C6F5Li).It will be demonstrated that strong and sterically encumbered Br�nsted bases such as zwitterionic and non-zwitterionic carbanions, N-heterocyclic carbenes and phosphonium ylides form intermolecular FLPs with fluorine free boron-containing Lewis acids capable of cleaving H2. Our experimental and computational results clearly show that even poor Lewis acids engage in H2 cleavage provided that the present base is sterically encumbered and of sufficiently high Br�nsted basicity. This FLP approach - weak Lewis acid combined with a strong base - is inverse to that pioneered and exhaustively studied by Stephan, Erker and others the latter utilizes FLPs composed of the exceptionally strong Lewis acids B(C6F5)3 or RB(C6F5)2 and weakly basic amines and phosphines.

Heterolytic cleavage of molecular dihydrogen via an "inverse" frustrated Lewis pair (FLP) approach

247th National Meeting (2014)

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