Speciation of ZnMe2, ZnMeCl, and ZnCl2 in Tetrahydrofuran (THF), and Its Influence on Mechanism Calculations of Catalytic Processes

Abstract

This paper examines the speciation of ZnMe2, ZnMeCl, and ZnCl2 in tetrahydrofuran (THF) solution, and provides experimental (infrared (IR) and calorimetric experiments) and density functional theory (DFT) data to conclude that the species in THF solution are, beyond a doubt, ZnMe2(THF)2, ZnMeCl(THF)2, and ZnCl2(THF)2. Consequently, coordinated THF should be used in DFT mechanistic calculations (e.g., Negishi reactions in THF). Naked or single THF coordinated molecules are virtually nonexistent in THF solutions. A cluster-continuum model for the solvent is recommended to obtain a more-correct representation. The presence or absence of THF produces a marked effect on the thermodynamics of the Negishi catalysis and a lesser effect on the kinetics of the transmetalation.