A Reaction Mechanism for Oxidative Addition of Halogen to Platinum(II), Reductive Elimination of Halide from Platinum(IV) and Halide Assisted Anations of Platinum(IV) Complexes

• The oxidative addition of iodine to Pt(CN)42− is first-order with respect to iodide, iodine and complex. The reverse reductive elimination of iodide from trans-Pt(CN)4I22- is first-order with respect to iodide and Pt(CN)4I22−. The kinetics for the reaction between bromide and trans-Pt(CN)4ClH2O2− involves a rate-determining reductive elimination of chloride, followed by a rapid oxidative addition of bromine to the formed Pt(CN)42−. The reactions between trans-Pt(CN)4BrH2O− and bromide or chloride can be described as halide assisted anations. The rate constant for the bromide anation is kexp = k′[Br−]2 and for the chloride anation (in the presence of bromide) k′[Br−][Cl−] + k′' [Cl−]2. All reactions were followed using a stopped-flow technique at 25°C in 0.50M perchloric acid medium. The equilibrium constant for the redox equilibrium between Pt(CN)42−, iodine and Pt(CN)4I22− was determined separately to be (1.29 ± 0.03) × 104M−1. Exploratory stopped-flow experiments indicate that the oxidative addition of chlorine to PtCl42− is first-order with respect to both chlorine and tetrachloroplatinate. The experimental rate laws can be described by a reaction mechanism which resembles that introduced previously for Pt(II)-catalyzed anations and substitutions, in that both mechanisms can be considered as oxidative additions/reductive eliminations.

• The oxidative addition of iodine to Pt(CN)42− is first-order with respect to iodide, iodine and complex. The reverse reductive elimination of iodide from trans-Pt(CN)4I22- is first-order with respect to iodide and Pt(CN)4I22−. The kinetics for the reaction between bromide and trans-Pt(CN)4ClH2O2− involves a rate-determining reductive elimination of chloride, followed by a rapid oxidative addition of bromine to the formed Pt(CN)42−. The reactions between trans-Pt(CN)4BrH2O− and bromide or chloride can be described as halide assisted anations. The rate constant for the bromide anation is kexp = k′[Br−]2 and for the chloride anation (in the presence of bromide) k′[Br−][Cl−] + k′' [Cl−]2. All reactions were followed using a stopped-flow technique at 25°C in 0.50M perchloric acid medium. The equilibrium constant for the redox equilibrium between Pt(CN)42−, iodine and Pt(CN)4I22− was determined separately to be (1.29 ± 0.03) × 104M−1. Exploratory stopped-flow experiments indicate that the oxidative addition of chlorine to PtCl42− is first-order with respect to both chlorine and tetrachloroplatinate. The experimental rate laws can be described by a reaction mechanism which resembles that introduced previously for Pt(II)-catalyzed anations and substitutions, in that both mechanisms can be considered as oxidative additions/reductive eliminations.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

Oxidative addition

Reductive elimination

Platinum(II)

Reaction mechanism

Halogen

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