College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, PR China.
J Am Chem Soc. 2009 Nov 25;131(46):16656-7. doi: 10.1021/ja908198d.
Organozinc halide reagents are not as simple as RZnCl. Differences in solution NMR spectra and kinetic behavior of phenyzinc halide reagents prepared from Grignard (1a system) and lithium reagents (1b system), respectively, were observed. In the 1a system, zero-order kinetic behavior indicates that transmetalation is not the rate-limiting step, while first-order kinetics were observed in the 1b system, and the transmetalation step proved to be rate-limiting. The structure of 1a was revealed by single-crystal X-ray diffraction analysis to contain (THF)(4)MgCl(2) complexed to PhZnX. DFT calculations suggest weaker Ph-Zn bonds in 1a than in 1b, consistent with the faster transmetalation process in catalytic reactions.
有机锌卤化物试剂并不像 RZnCl 那么简单。分别用格氏试剂（1a 体系）和锂试剂（1b 体系）制备的苯基金属卤化物试剂在溶液 NMR 谱和动力学行为上存在差异。在 1a 体系中，零级动力学行为表明转金属化不是限速步骤，而在 1b 体系中观察到一级动力学，并且转金属化步骤被证明是限速步骤。通过单晶 X 射线衍射分析揭示了 1a 的结构，其中包含（THF）（4）MgCl（2）与 PhZnX 配位。DFT 计算表明 1a 中 Ph-Zn 键比 1b 中弱，这与催化反应中转金属化过程更快一致。
