A Phosphanyl-Phosphagallene that Functions as a Frustrated Lewis Pair

Phosphagallenes (1 a/1 b) featuring double bonds between phosphorus and gallium were synthesized by reaction of (phosphanyl)phosphaketenes with the gallium carbenoid Ga(Nacnac) (Nacnac=HC[C(Me)N(2,6-i-Pr2C6H3)](2)). The stability of these species is dependent on the saturation of the phosphanyl moiety.1 a, which bears an unsaturated phosphanyl ring, rearranges in solution to yield a spirocyclic compound (2) which contains a P=P bond. The saturated variant1 bis stable even at elevated temperatures.1 bbehaves as a frustrated Lewis pair capable of activation of H(2)and forms a 1:1 adduct with CO2.