A Frustrated Phosphane-Borane Lewis Pair and Hydrogen: A Kinetics Study.

The energy profile of a FLP/H2 splitting system was determined by a combined experimental kinetic and a DFT study. A trimethylene-bridged P/B FLP 3 was converted to its endothermic H2-cleavage product 4 by sequential H+/H- addition. The system could be handled at low temperature and the kinetics of the H2-elimination were determined to give a rate constant of kHH,exp(299 K) = (2.87 ± 0.1) × 10-4 s-1 in solution and the primary kinetic isotope effects were determined [e.g. (kHH/kDD)exp = 3.19]. The system was accurately analyzed by DFT calculations.