Cycloneophylpalladium(IV) Complexes: Formation by Oxidative Addition and Selectivity of Their Reductive Elimination Reactions

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.