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

Abstract

The phosphino-phosphenium cation (PPC) [Ph₃PPPh₂][GaCl₄] reacts as a frustrated Lewis pair to add across the NN bond of (tBuO₂CN)₂. In contrast, photolytical addition [Ph₂ClPPPh₂][GaCl₄] to (RN)₂ results in cleavage of the NN bond affording [Ph₂P(μ-NR)₂PPh₂Cl][GaCl₄] (R = Ph 2, C₆H₄Cl₃). While the chloride of 2 is replaced with N₃ or CN via reaction with Me₃SiN₃ or tBuNC respectively, reaction with (C₆F₅)₂BH effects ring opening to give [HN(Ph)PPh₂(μ-NPh)PPh₂][GaCl₄] 7. This reactivity demonstrates that PPCs behave as FLPs to effect either addition or cleavage of NN double bonds.