The Methyl(cyclam)nickel(III) Dication in Aqueous Solutions: Determination of the Equilibrium Constant of Homolysis, Kinetics of O₂ Insertion, and Methyl Transfer to Cr²⁺ _aq

The reaction of methyl radicals with LNi²⁺, L = cyclam, proceeds via LNi²⁺ + ^.CH₃ ⇋ L(H₂O)Ni^III-CH₃²⁺, K = 1.1 × 10⁷ M^-1, ^.CH₃ + L(H₂O)Ni^III-CH₃²⁺ → LNi²⁺ + C₂H₆. In the presence of dioxygen L(H₂O)Ni^III-CH₃²⁺ decomposes via homolysis followed by O₂ + ^.CH₃ → ^.O₂CH₃ and ^.O₂CH₃ + LNi²⁺ → L(H₂O)Ni^III-O₂CH₃²⁺. L(H₂O)Ni^III-CH₃²⁺ reacts with Cr(H₂O)₆²⁺ via L(H₂O)Ni^III-CH₃²⁺ + Cr(H₂O)₆²⁺ → LNi²⁺ + (H₂O)₅Cr^III-CH₃²⁺. The kinetics of these reactions and the properties of the new intermediates are discussed, and their relevance as models for biological systems is pointed out.