双烃基硫桥六羰基二铁化合物亲核取代反应动力学研究

本文用分光光度法和核磁共振法研究了三种双烃基硫桥六羰基二铁—(μ,μ—SCH_2S)Fe_2(CO)_6, (μ—phCH_2S)(μ—RS)Fe_2(CO)_6(R=Me, Et)—与一系列膦配体在三种有机溶剂中进行亲核取代反应的动力学。提出了反应机理, 讨论了配体的电子因素、空间因素以及溶剂效应对取代反应速率和机理的影响。

STUDY ON THE KINETICS AND MECHANISMS OF THE SUBSTITUTION REACTIONS OF SOME DI-ALKYLTHIOLATOHEXACARBONYLDIIRON COMPLEXES

The kinetics and mechanisms of the substitution reactions of (μ,μ-SCH_2S)Fe_2 (CO)_6 with PPh_3, PMe_2Ph, PEt_3, P(n-Bu)_3 and (μ-PhCH_2S)(μ-RS)Fe_2(CO)_6(R=Me, Et) with PPh_3 in various solvents have been studied by means of UV-spectra and ~1H NMR. The results support the mechanism of Ia (associative interchange) for the substitution reactions of first step and Id (dissociative interchange) for the reactions of second step. The electronic effects of the ligands, steric effects of the ligands and the parent complexes and the solvent effecs on the reaction rates have been discussed. It shows that the reaction rate is presumably determined by the volume of the incoming ligands. the nucleophilic solvents such as DMF can promote the reaction rate by means of base catalysis.