Cationic iridium diolefin complexes as alkene hydrogenation catalysts and the isolation of some related hydrido complexes

Abstract

In non-coordinating solvents, such as CH 2Cl 2, the complexes [Ir(cod)L 2]PF 6 (I) and [Ir(cod)L(py)]PF 6 (II) (cod  1,5-cyclooctadiene; py  pyridine, L  tertiary phosphine) are very active homogeneous hydrogenation catalysts for alkenes. When the alkene has been consumed, or, in certain cases, only partially consumed, the catalyst is irreversibly deactivated; the metal-containing product from I is [Ir2(μ-H) 3H 2L 2]PF 6 (III). With HCI, III gives [Ir 2(μ-Cl) 2(μ-H)H 2L 4]PF 6. The catayst system from I gives the isolable complexes [IrH 5L 2) with NEt 3, while that from II gives these complexes in the presence of NEt 3 and an excess of L.