Iridium complexes of orthometalated triaryl phosphites: Synthesis, structure, reactivity, and use as imine hydrogenation catalysts

Di-orthometalated iridium complexes of triaryl phosphites have been prepared and characterized. The synthesis of the triphenyl phosphite derivative [IrH(cod){P(OC6H4)(2)(OC6H5)}], 3, requires a circuitous route by treatment of [IrCl(cod){P(OPh)(3)}] with methyllithium and then methanol. However, with the hindered phosphites P(OAr)(3) (Ar = C6H4-2-(t)Bu or C6H3-2,4-(t)Bu(2)) the di-orthometalated species 5a,b are readily obtained by reaction of the phosphite with [{Ir(mu-OMe)(cod)}(2)] or [Ir(cod)(py)(2)][PF6]. The mechanisms of these reactions have been investigated and are different. Both 5a and 5b are catalysts for imine hydrogenation. The complexes [IrH5{P(OAr)(3)}(2)] have been isolated from hydrogenation reactions and synthesized independently.