Abstract
N-heterocyclic phosphines (NHPs), and especially their ionic derivatives, phosphenium cations, have gained significant attention not only as isoelectronic species to N-heterocyclic carbenes (NHCs) but mainly, as highly Lewis acidic, active organocatalysts. A novel type of saturated NHPs has been introduced, with the nitrogen atoms substituted by phosphoramidothioates-{[κ(2)-O,O-(OCH(2)C(Me)(2)CH(2)O)P(= S)](2)-μ-[NCH(2)CH(2)N]}PX, where X = F, Cl, Br, I, H, Ph, and their derivatives. Thanks to an increased positive charge at the P(III) atom, these compounds are prone to activate C─O, B─H, B─C, or B─F bonds and open cyclic ethers through the formation of intermediate species-phosphenium cations. The hydrido derivative can effectively catalyze the transfer hydrogenation of azobenzene by ammonia borane when irradiated by UV light at room temperature. The self-ionization of the iodido derivative promoted by the coordination of less sterically demanding N-heterocyclic carbene enables the isolation of a phosphenium cation.