Reactivity of an Unsaturated Iridium(III) Phosphoramidate Complex, [Cp*Ir{κ2N,O}][BArF4]

The three-legged piano stool complex [Cp*Ir­(κ2-N,O-Xyl­(N)­P­(O)­(OEt)2)­(Cl)], [1] (Cp* = η5-C5Me5, Xyl = 2,6-dimethylphenyl), was prepared from reaction of 0.5 equiv of [Cp*IrCl2]2 with the sodiated phosphoramidate ligand Na­[Xyl­(N)­P­(O)­(OEt)2]. Treatment of [1] with Na­[BArF4], [BArF4] = [B­(C6H3(CF3)2)4], led to the formation of the 16-electron two-legged piano stool species [Cp*Ir­(κ2-N,O-Xyl­(N)­P­(O)­(OEt)2)]­[BArF4], [2]­[BArF4], which was characterized in both solution and solid state. Reactivity screening revealed that complex [2]­[BArF4] undergoes addition of a variety of Lewis bases to afford the corresponding 18-electron adducts with concomitant movement of the phosphoramidate ligand from κ2-N,O to κ1-N, [Cp*Ir­(κ1-N-Xyl­(N)­P­(O)­(OEt)2)­(L)2]­[BArF4]; L = CNtBu, [3]­[BArF4], CNXyl, [4]­[BArF4], MeCN, [7]­[BArF4], bipy, [8]­[BArF4]; bipy = 2,2′-bipyridine. For complex [7]­[BArF4], variable-temperature 31P­{1H} NMR spectroscopy revealed that MeCN coordination was reversible between 238 and 190 K. To probe E–H (E = Si, B) bond activation, complex [2]­[BArF4] was treated with H2SiPh2, providing the five-membered iridacycle [Cp*Ir­(κ2-N,Si-Xyl­(N)­P­(OSiPh2)­(OEt)2)]­[BArF4], [9]­[BArF4], via geminal Si–H activation, while use of mesityl borane, H2BMes (Mes = 2,4,6-trimethylphenyl), afforded the six-membered phosphoramidate-stabilized borane complex [Cp*Ir­(κ3-N,H,H-Xyl­(N)­P­(OBH2Mes)­(OEt)2)]­[BArF4], [10]­[BArF4]. Complexes [3]­[BArF4] and [9]­[BArF4] were additionally characterized by single-crystal X-ray diffraction.