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

The three-legged piano stool complex [Cp*Ir­(κ²-<i>N</i>,<i>O</i>-Xyl­(<u>N</u>)­P­(<u>O</u>)­(OEt)₂)­(Cl)], [<b>1</b>] (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 [<b>1</b>] 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-<i>N</i>,<i>O</i>-Xyl­(<u>N</u>)­P­(<u>O</u>)­(OEt)₂)]­[BAr^F₄], [<b>2</b>]­[BAr^F₄], which was characterized in both solution and solid state. Reactivity screening revealed that complex [<b>2</b>]­[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-<i>N</i>,<i>O</i> to κ¹-<i>N</i>, [Cp*Ir­(κ¹-<i>N</i>-Xyl­(<u>N</u>)­P­(O)­(OEt)₂)­(L)₂]­[BAr^F₄]; L = CN<i>t</i>Bu, [<b>3</b>]­[BAr^F₄], CNXyl, [<b>4</b>]­[BAr^F₄], MeCN, [<b>7</b>]­[BAr^F₄], bipy, [<b>8</b>]­[BAr^F₄]; bipy = 2,2′-bipyridine. For complex [<b>7</b>]­[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 [<b>2</b>]­[BAr^F₄] was treated with H₂SiPh₂, providing the five-membered iridacycle [Cp*Ir­(κ²-<i>N,Si</i>-Xyl­(<u>N</u>)­P­(O<u>Si</u>Ph₂)­(OEt)₂)]­[BAr^F₄], [<b>9</b>]­[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-<i>N,H,H</i>-Xyl­(<u>N</u>)­P­(OB<u>H</u>_<u>2</u>Mes)­(OEt)₂)]­[BAr^F₄], [<b>10</b>]­[BAr^F₄]. Complexes [<b>3</b>]­[BAr^F₄] and [<b>9</b>]­[BAr^F₄] were additionally characterized by single-crystal X-ray diffraction