A Rare Example of Efficient Alkene Hydrogenation Mediated by a Neutral Iridium(I) Complex under Mild Conditions

The synthesis and characterization of two new square-planar (COD)M(κ2-P,O-phosphinoenolate) complexes (M = Rh, 3a; M = Ir, 3b; COD = η4-1,5-cyclooctadiene) are described. Complex 3b represents an unusual example of a neutral (not cationic) square-planar Ir(I) complex that is capable of mediating the reduction of alkenes under mild benchtop conditions (∼1 atm of H2, 22 °C) in the presence of high-polarity (THF, CH2Cl2, CH3CN) and low-polarity solvents (hexanes, benzene).