Cycloneophylpalladium(IV) complexes: Formation by oxidative addition and selectivity of their reductive elimination reactions
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The cycloneophylpalladium(II) complexes [Pd(CH2CMe2C6H4)(κ2-N,N′-L)] (L = RO(CH2)3N(CH2-2-C5H4N)2, R = H, Me) undergo oxidation to Pd(IV) with bromine or iodine to give [PdX(CH2CMe2C6H4)(κ3-N,N′,N″-L)]X (X = Br, I) or with methyl iodide to give the transient complexes [PdMe(CH2CMe2C6H4)(κ3-N,N′,N″-L)]I. The products of Br2 and I2 oxidation, [PdX(CH2CMe2C6H4)(κ3-N,N′,N″-L)]X (X = Br, I), are sufficiently stable to be isolated, but they decompose slowly in solution by reductive elimination to give the palladium-(II) products [PdX(κ3-N,N′,N″-L)]X (X = Br, I). The organic products are formed via either CH2-Ar or CH2-X bond formation. In the latter case, neophyl rearrangement and protonolysis steps follow reductive elimination to give a mixture of organic products. The methylpalladium(IV) complexes [PdMe(CH2CMe2C6H4)(κ3-N,N′,N″-L)]I decompose at 0 °C by selective reductive elimination with Me-Ar bond coupling to give the alkylpalladium(II) complex [Pd(CH2CMe2-2-C6H4Me)(κ3-N,N′,N″-L)]I. The mechanisms of the reactions have been explored by kinetic studies.