Functional phosphines. Part XIV. Cationic (P,N)2-coordinated hydrides of iridium(III): catalysts for CO hydrogenation or transfer hydrogenation?

Treatment of trans-[IrCl(CO)(PPh3)2] with Ph2PCH2CH2NH2 in refluxing para-xylene gave (OC-6-43)-[Ir(H)(Cl)(Ph2PCH2CH2NH2)2]Cl (1) which interacted with K[BH(s-Bu3)] to produce a mixture of (OC-6-22)-[IrH2(Ph2PCH2CH2NH2)2]Cl (2a) and (OC-6-32)-[Ir(H)(Cl)(Ph2PCH2CH2NH2)2]Cl (2b). The trans-dihydride 2a was isolated in pure form from the reaction between 1 and KOH/i-PrOH. Different from its isoelectronic (P,N)2-coordinated RuII analogues, the cationic chloro hydrido complex 1 does not act as a catalyst for the direct hydrogenation of acetophenone by molecular H2, if activated by strong alkoxide base, but rather catalyzes the transfer hydrogenation of the CO bond with methanol or isopropanol as proton/hydride sources. Dihydrido complex 2a is ascribed the role of the actual catalyst as it supports the transfer hydrogenation reaction even in the absence of base. The crystal structure of the addition compound 1 · 2EtOH has been determined.