Cyclometalated iridium complexes based on monodentate aminophosphanes.

Monodentate aminophosphanes HNP [NH(4-tolyl)PPh] and SiMeNP [SiMeN(4-tolyl)PPh] react with [Ir(μ-Cl)(cod)] affording tetra- or pentacoordinate complexes of formula [IrCl(L)(cod)] (L = HNP, = 1, 2; L = SiMeNP, = 1). The reaction of [IrCl(SiMeNP)(cod)] with carbon monoxide smoothly renders [Ir(CO)(SiMeNP)][IrCl(CO)]. The reaction of HNP or SiMeNP with [Ir(CHCN)(cod)][PF] yields the cyclometalated iridium(III)-hydride derivatives [IrH{κ,-NR(4-CHCH)PPh}(cod)(CHCN)][PF] (R = H, SiMe) as a result of the intramolecular oxidative addition of the tolyl C-H bond to iridium. The straighforward formation of [IrH{κ,-SiMeN(4-CHCH)PPh}(cod)(CHCN)] was observed when the reaction was monitored by NMR spectroscopy at 233 K, whereas a more complex reaction sequence was observed in the formation of [IrH{κ,-NH(4-CHCH)PPh}(cod)(CHCN)], including the formation of [IrH{κ,-NH(4-CHCH)PPh}(HNP)(cod)] and [Ir(cod)(HNP)]. The "mixed" complex [IrH{κ,-SiMeN(4-CHCH)PPh}(HNP)(cod)] was obtained upon reaction of [IrH{κ,-NH(4-CHCH)PPh}(cod)(CHCN)][PF] with SiMeNP at 233 K. Finally, the reaction of [Ir(CHCN)(coe)][PF] with SiMeNP or HNP resulted in the formation of [Ir(CHCN)(SiMeNP)][PF] and [IrH{κ,-NH(4-CHCH)PPh}(HNP)(CHCN)][PF], respectively. Both the -6-35 and the -6-52 isomers of [IrH{κ,-NH(4-CHCH)PPh}(HNP)(CHCN)] - featuring facial and meridional dispositions of the phosphorus atoms, respectively - were isolated depending on the reaction solvent. Several compounds described herein catalyse the dehydrogenation of formic acid in DMF, [IrCl(HNP)(cod)] being the most active, with TOF of about 2300 h (5 mol% catalyst, 50 mol% sodium formate, DMF, 80 °C).