Dihydrogen Activation with ^<i>t</i>Bu₃P/B(C₆F₅)₃: A Chemically Competent Indirect Mechanism via in Situ-Generated <i>p</i>-^<i>t</i>Bu₂P–C₆F₄–B(C₆F₅)₂

A chemically competent indirect pathway for the activation of dihydrogen by the nonmetal Lewis acid/Lewis base pair tBu3P/B(C6F5)3 is described. The reaction between tBu3P and B(C6F5)3 produces [tBu3PH]+[FB(C6F5)3]− and the known phosphinoborane p-tBu2P–C6F4–B(C6F5)2 (1-tBu) with elimination of isobutylene. At 1:1 stoichiometry, 1-tBu is produced rapidly in detectable quantities and can act as a catalyst for the formation of [tBu3PH]+[HB(C6F5)3]− from tBu3P and B(C6F5)3 in the presence of H2. The extent to which this indirect path competes with the direct path is explored.