Late-metal nitrosyl cations: Synthesis and reactivity of [Ni(NO)(MeNO 2)3][PF6]

Article abstract of DOI:10.1021/ic201821t

The reaction of [NO][PF₆] with excess Ni powder in CH ₃NO₂, in the presence of 2 mol % NiI₂, results in the formation of [Ni(NO)(CH₃NO₂)₃][PF ₆] (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) A]. 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-Me₃C ₆H₃)(NO)][PF₆] (6). In the solid state, complex 6 exhibits a long Ni-C_cent distance [1.682(2) A], 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-C_cent distance [1.684(1) A].