Reactivity of an Unsaturated Iridium(III) Phosphoramidate Complex, [Cp*Ir{κ2-N,O}][BAr4F]

The three-legged piano stool complex [Cp*Ir(kappa(2)-N,O-Xyl(N)P(O)(OEt)(2))(Cl)], [1] (Cp* = eta(5)-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[BAr4F], [BAr4F] = [B(C6H3(CF3)(2))(4)], led to the formation of the 16-electron two-legged piano stool species [Cp*Ir(kappa(2)-N,O-Xyl(N)P(O)(OEt)(2))][BAr4F], [2] [BAr4F], which was characterized in both solution and solid state. Reactivity screening revealed that complex [2] [BAr4F] undergoes addition of a variety of Lewis bases to afford the corresponding 18-electron adducts with concomitant movement of the phosphoramidate ligand from kappa(2)-N,O to kappa(1)-N, [Cp*Ir(kappa(1)-N-Xyl(N)P(O)(OEt)(2))(L)(2)][BAr4F]; L = CNtBu, [3][BAr4F], CNXyl, [4][BAr4F], MeCN, [7][BAr4F], bipy, [8][BAr4F]; bipy = 2,2'-bipyridine. For complex [7][BAr4F], variable-temperature P-31{H-1} NMR spectroscopy revealed that MeCN coordination was reversible between 238 and 190 K. To probe E-H (E = Si, B) bond activation, complex [2][BAr4F] was treated with H2SiPh2, providing the five-membered iridacyde [Cp*Ir(kappa(2)-N,Si-Xyl(N)P(OSiPh2)(OEt)(2))][BAr4F], [9][BAr4F], via geminal Si-H activation, while use of mesityl borane, H(2)BMes (Mes = 2,4,6-trimethylphenyl), afforded the six-membered phosphoramidate-stabilized borane complex [Cp*Ir(kappa(3)-N,H,H-Xyl(N)P(OBH(2)Mes)(OEt)(2))][BAr4F], [10][BAr4F]. Complexes [3][BAr4F] and [9][BAr4F] were additionally characterized by single-crystal X-ray diffraction.