Rates of the Oxidative Addition of Benzyl Halides to a Metallacyclic Palladium(II) Complex and of the Reductive Elimination from a Benzyl-Palladium(IV) Complex.

Pd(II) metallacyclic complexes are key intermediates in sequential reactions in which three new C−C bonds are formed in an aromatic ring. The Pd(II) metallacyclic complex 10with phenanthroline as ligand undergoes oxidative addition to benzyl bromide or chloride in DMF to generate benzyl-Pd(IV) complexes. The rate constant of the oxidative addition is determined by means of electrochemical techniques, with the expected reactivity order PhCH 2Br ( k1Br= 3.6 M −1s −1) > PhCH 2Cl ( k1Cl= 6 × 10 −3M −1s −1) at 29 °C. When the benzyl-Pd(IV) complex is generated from PhCH 2Br, the oxidative addition is followed by a slow C−C reductive elimination, which gives a Pd(II) complex. The rate constant of the reductive elimination has been determined in DMF ( k2Br= 6 × 10 −4s −1) at 29 °C. [ABSTRACT FROM AUTHOR]