Reactivity of an Unsaturated Iridium(III) Phosphoramidate Complex, [Cp*Ir{κ²‑N,O}][BAr^F₄]

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[BAr^F₄], [BAr^F₄] = [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)]­[BAr^F₄], [2]­[BAr^F₄], which was characterized in both solution and solid state. Reactivity screening revealed that complex [2]­[BAr^F₄] 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]­[BAr^F₄]; L = CNtBu, [3]­[BAr^F₄], CNXyl, [4]­[BAr^F₄], MeCN, [7]­[BAr^F₄], bipy, [8]­[BAr^F₄]; bipy = 2,2′-bipyridine. For complex [7]­[BAr^F₄], 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]­[BAr^F₄] was treated with H₂SiPh₂, providing the five-membered iridacycle [Cp*Ir­(κ²-N,Si-Xyl­(N)­P­(OSiPh₂)­(OEt)₂)]­[BAr^F₄], [9]­[BAr^F₄], 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)]­[BAr^F₄], [10]­[BAr^F₄]. Complexes [3]­[BAr^F₄] and [9]­[BAr^F₄] were additionally characterized by single-crystal X-ray diffraction.