title: Transmetalation is the rate-limiting step: quantitative kinetic investigation of nickel-catalyzed oxidative coupling of arylzinc reagents.
abstract: Transmetalation is the rate-limiting step! The transmetalation between arylzinc reagents and ArNi(II)R was confirmed as the rate-limiting step in the nickel-catalyzed oxidative coupling reactions. It was proved to be an excellent model allowing the first quantitative measurement of the kinetic rate constants of transmetalation from a live catalytic system. Rate constants from 0.04 to 0.31 M(-1) s(-1) were obtained for different arylzinc reagents under the conditions, and the activation enthalpy DeltaH(++) was 14.6 kcal/mol for PhZnCl. The substituent effect on the transmetalation was also gained for the first time from the catalytic reaction.
authors.affiliation: College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China.
authors.forename: Liqun
authors.initials: L
authors.lastname: Jin
authors.forename: Jie
authors.initials: J
authors.lastname: Xin
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Huang
authors.forename: Jun
authors.initials: J
authors.lastname: He
authors.forename: Aiwen
authors.initials: A
authors.lastname: Lei