Addition and N=N bond cleavage of diazo-compounds by phosphino-phosphenium cations

The phosphino-phosphenium cation (PPC) [Ph3PPPh2][GaCl4] reacts as a frustrated Lewis pair to add across the NN bond of (tBuO(2)CN)(2). In contrast, photolytical addition [Ph2ClPPPh2][GaCl4] to (RN)(2) results in cleavage of the NN bond affording [Ph2P(mu-NR)(2)PPh2Cl][GaCl4] (R = Ph 2, C6H4Cl3). While the chloride of 2 is replaced with N-3 or CN via reaction with Me3SiN3 or tBuNC respectively, reaction with (C6F5)(2)BH effects ring opening to give [HN(Ph)PPh2(mu-NPh)PPh2][GaCl4] 7. This reactivity demonstrates that PPCs behave as FLPs to effect either addition or cleavage of NN double bonds.