An isolable phosphaalumene(3) capable of small molecule activation via unique modes of reactivity

The chemistry of phosphaalumenes [R-Al=P-R'] featuring multiple bonds between phosphorus and aluminum remains largely unexplored. Here we show the syntheses of a phosphaalumene(3) through either the reaction of ^DippNacNacM (^DippNacNac = HC[(CMe)N(2,6-ⁱPr₂C₆H₃)]₂, M = Al) with a bisphosphirane-fused anthracene (1) or with a phospha-Wittig reagent (2) under mild conditions. This phosphaalumene exhibits reactivities that stand in contrast to those of previously reported transient species II, especially in its ability to activate small molecules such as dihydrogen (H₂), white phosphorus (P₄), isocyanides, CO₂, N₂O, trimethylsilyl azide (TMSN₃), diphenyl diselenide (PhSeSePh), PhSiH₃, PhNH₂, styrene and 1-ethynyl-4-methylbenzene. It has been found in this research that the ligand environment can have a subtle but profound impact on the reactivity of phosphaalumenes.