Cyclometalated iridium complexes based on monodentate aminophosphanes.

Monodentate aminophosphanes HNP [NH(4-tolyl)PPh 2 ] and SiMe 3 NP [SiMe 3 N(4-tolyl)PPh 2 ] react with [Ir(μ-Cl)(cod)] 2 affording tetra- or pentacoordinate complexes of formula [IrCl(L) n (cod)] (L = HNP, n = 1, 2; L = SiMe 3 NP, n = 1). The reaction of [IrCl(SiMe 3 NP)(cod)] with carbon monoxide smoothly renders [Ir(CO) 3 (SiMe 3 NP) 2 ][IrCl 2 (CO) 2 ]. The reaction of HNP or SiMe 3 NP with [Ir(CH 3 CN) 2 (cod)][PF 6 ] yields the cyclometalated iridium(III)-hydride derivatives [IrH{κ 2 C , P -NR(4-C 6 H 3 CH 3 )PPh 2 }(cod)(CH 3 CN)][PF 6 ] (R = H, SiMe 3 ) as a result of the intramolecular oxidative addition of the tolyl C 2 -H bond to iridium. The straighforward formation of [IrH{κ 2 C , P -SiMe 3 N(4-C 6 H 3 CH 3 )PPh 2 }(cod)(CH 3 CN)] + 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 2 C , P -NH(4-C 6 H 3 CH 3 )PPh 2 }(cod)(CH 3 CN)] + , including the formation of [IrH{κ 2 C , P -NH(4-C 6 H 3 CH 3 )PPh 2 }(HNP)(cod)] + and [Ir(cod)(HNP) 2 ] + . The "mixed" complex [IrH{κ 2 C , P -SiMe 3 N(4-C 6 H 3 CH 3 )PPh 2 }(HNP)(cod)] + was obtained upon reaction of [IrH{κ 2 C , P -NH(4-C 6 H 3 CH 3 )PPh 2 }(cod)(CH 3 CN)][PF 6 ] with SiMe 3 NP at 233 K. Finally, the reaction of [Ir(CH 3 CN) 2 (coe) 2 ][PF 6 ] with SiMe 3 NP or HNP resulted in the formation of [Ir(CH 3 CN) 2 (SiMe 3 NP) 2 ][PF 6 ] and [IrH{κ 2 C , P -NH(4-C 6 H 3 CH 3 )PPh 2 }(HNP) 2 (CH 3 CN)][PF 6 ], respectively. Both the OC -6-35 and the OC -6-52 isomers of [IrH{κ 2 C , P -NH(4-C 6 H 3 CH 3 )PPh 2 }(HNP) 2 (CH 3 CN)] + - 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) 2 (cod)] being the most active, with TOF 1 min of about 2300 h -1 (5 mol% catalyst, 50 mol% sodium formate, DMF, 80 °C).