Synthesis and reactions of ene–hydrazone diphosphine iridium complexes and related species†

Treatment of the azine diphosphine Z,Z-PPh2CH2C(But)N–NC(But)CH2PPh2 I with [IrCl(CO)2(H2NC6H4Me-4)] in benzene gave the ene–hydrazone diphosphine iridium(III) hydride [IrH(Cl)(CO){PPh2CHC(But)N–NC(But)CH2PPh2}], 1, which isomerised reversibly to the ionic square planar iridium(I) complex [Ir(CO){PPh2CH2C(But)N–NC(But)CH2PPh2}]Cl 2a, containing an azine diphosphine. Treatment of 1 with NEt3 gave the neutral ene–hydrazone diphosphine iridium(I) complex [Ir(CO){PPh2CHC(But)N–NC(But)CH2PPh2}] 3 which is reactive and undergoes oxidative addition of H2 to give the iridium(III) dihydride mer,cis-[IrH2(CO){PPh2CH C(But)N–NC(But)CH2PPh2}] 4 and oxidative addition of MeI to give the methyliridium(III) complex [IrMe(I)(CO){PPh2CHC(But)N–NC(But)CH2PPh2}] 5. It reacted rapidly with olefins or acetylenes (L), i.e.N-methylmaleimide, ethene or dimethyl acetylenedicarboxylate, to give the five-co-ordinate adducts [Ir(CO)L{PPh2CH C(But)N–NC(But)CH2PPh2}], 6a, 6b or 6c, respectively, also with O2 to give the η2-dioxygen adduct [Ir(CO)(η2-O2){PPh2CHC(But)N–NC(But)CH2PPh2}] 7. Treatment of 3 with 1 mol of picric acid protonated the ene–hydrazone diphosphine backbone to give the azine diphosphine iridium(I) salt [Ir(CO){PPh2CH2C(But)N–N C(But)CH2PPh2}][OC6H2(NO2)3] 2b. The N-methylmaleimide adduct 6a was similarly protonated to give the corresponding azine diphosphine iridium(I) salt [Ir(CO)(η2-COCHCHCONMe){PPh2CH2C(But)N–NC(But)CH2PPh2}][OC6H2(NO2)3] 8. Complex 1 was protonated by HCl to give the corresponding azine diphosphine iridium(III) salt [IrH(Cl)(CO){PPh2CH2C(But)N–NC(But)CH2PPh2}]Cl 9a, which is converted into 3 when treated with NEt3. The 1H, 13C and 31P NMR and some IR data are given.