Diphosphinoboranes as Intramolecular Frustrated Lewis Pairs: P-B-P Bond Systems for the Activation of Dihydrogen, Carbon Dioxide, and Phenyl Isocyanate.

Herein, we present the first example of the activation of small molecules by P-B-P bond systems. The reactivity study involves reactions of two selected diphosphinoboranes, (-BuP)BPh () and (CyP)BNPr (), that differ in terms of their structural and electronic properties for the activation of dihydrogen, carbon dioxide, and phenyl isocyanate. Diphosphinoborane activates H under very mild conditions in the absence of a catalyst with the formation of the dimer (-BuPB(Ph)H) and -BuPH. Conversely, diphosphinoborane did not react with H under the same conditions. The reaction of with CO led to the formation of a compound with an unusual structure, where two phosphinoformate units were coordinated to the PhBOBPh moiety. In addition, reacted with CO to insert two CO molecules into the P-B bonds of the parent diphosphinoborane. Both diphosphinoboranes activated PhNCO, yielding products resulting from the addition of two and/or three PhNCO molecules and the formation of new P-C, B-O, B-N, and C-N bonds. The products of the activation of small molecules by diphosphinoboranes were characterized with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy, single-crystal X-ray diffraction, and elemental analysis. Additionally, the reaction mechanisms of the activation of small molecules by diphosphinoboranes were elucidated by theoretical methods.