Late-Metal Nitrosyl Cations: Synthesis and Reactivity of [Ni(NO)(MeNO2)3][PF6]

The reaction of [NO]­[PF6] with excess Ni powder in CH3NO2, in the presence of 2 mol % NiI2, results in the formation of [Ni­(NO)­(CH3NO2)3]­[PF6] (1), which can be isolated in modest yield as a blue crystalline solid. Also formed in the reaction is [Ni­(CH3NO2)6]­[PF6]2 (2), which can be isolated in comparable yield as a pale-green solid. In the solid state, 1 exhibits tetrahedral geometry about the Ni center with a linear nitrosyl ligand [Ni1–N1–O1 = 174.1(8)°] and a short Ni–N bond distance [1.626(6) Å]. As anticipated, the weakly coordinating nitromethane ligands in 1 are easily displaced by a variety of donors, including Et2O, MeCN, and piperidine (NC5H11). More surprisingly, the addition of mesitylene to 1 results in the formation of an η6-coordinated nickel arene complex, [Ni­(η6-1,3,5-Me3C6H3)­(NO)]­[PF6] (6). In the solid state, complex 6 exhibits a long Ni–Ccent distance [1.682(2) Å], suggesting a relatively weak Ni–arene interaction, a consequence of the strong π-back-donation to the nitrosyl ligand. The addition of anisole to 1 also results in the formation of a η6 nickel arene complex, [Ni­(η6-MeOC6H5)­(NO)]­[PF6] (7). This complex also exhibits a long Ni–Ccent distance [1.684(1) Å].