Kinetic And Mechanism Research Of Elementary Reactions In Coupling Reactions Involving Organozinc Reagents

Physical organic chemistry was the theory basis in the development of organic chemistry, while organometallic chemistry was the research object of physical organic chemistry. A lot of questions have to be solved urgently in organometallic chemistry. The key of solving these questions was to pursue an in-depth comprehension of elementary reactions. In this thesis, with in-situ IR as the primary kinetic tool, combining the UV-vis and X-ray absorption, it has been investigated on the kinetic and mechanism of elementary reactions in coupling reactions involing organozinc reagents. The detailed contents are as follows:1. With Pd-catalyzed the coupling reaction of aryl iodides with arylzinc reagent as model reaction. Kinetic investigations through in-situ IR revealed that the transmetalation between Ar’ZnCl and [Ar2-Pd-I] was confirmed as the rate-limiting step. Hence, the observed rate constants for transmetalation of the reactions involving different arylzinc reagents have been achieved. Furthermore, quantitative kinetic studies at different temperatures enabled us to acquire the activation energy as a value of 11.3 kcal/mol for the transmetalation of Ar1ZnCl with [Ar2-Pd-I].2. With Pd-catalyzed oxidative coupling reaction of arylzinc reagents as model reaction, with desyl chloride as oxidant, kinetic investigations through in-situ IR suggested that the transmetalation between [ArZnCl] and [Ar-Pd-R] was confirmed as the rate-limiting step. Hence, the observed rate constants for the transmetalation of different substituted arylzinc reagents have been achieved. Furthermore, quantitative kinetic studies at different temperatures enabled us to acquire the activation energy as a value of 12.3 kcal/mol for the transmetalation of ArZnCl with [Ar-Pd-R].3. With Co-catalyzed oxidative coupling reaction of arylzinc reagents as model reaction, with TEMPO as oxidant, X-ray absorption near-edge structure spectroscopic (XANES) evidence was provided for the active species of Co(II) in the catalytic reaction, a Co(0)/Co(II) catalytic cycle was firstly demonstrated for the Co-catalyzed oxidative coupling reaction of ArZnCl with TEMPO as oxidant. Kinetic studies through in-situ IR suggested that the transmetallation between ArZnCl and [Ar-ConII-Ln] was the rate-limiting step. Hence, the observed rate constants for the transmetalation of different substituted arylzinc reagents have been achieved. Furthermore, quantitative kinetic studies at different temperatures enabled us to acquire the activation energy as a value of 5.5 kcal/mol for the transmetalation of ArZnCl with [Ar-ConII-Ln].