Eklund John C., Bond Alan M., Colton Ray, Humphrey David G., Mahon Peter J., Walter Jacky N.
Department of Chemistry, Monash University, Clayton, Victoria 3168, Australia, and Department of Chemistry, La Trobe University, Bundoora, Victoria 3083, Australia.
Inorg Chem. 1999 May 3;38(9):2005-2011. doi: 10.1021/ic980796r.
The electrochemical oxidation of cis,mer-[Mn(CO)(2)(eta(1)-dpm)(eta(2)-dpm)Br] (dpm = Ph(2)PCH(2)PPh(2)), or (cis,mer)(0),()()has been examined in dichloromethane (0.1 M Bu(4)NPF(6)) by voltammetric, bulk electrolytic, in situ and ex situ spectroelectrochemical and simulation techniques. On the voltammetric time scale at 20 degrees C, the neutral 18-electron cis,mer Mn(I) species is oxidized to the corresponding 17-electron cation which at slow scan rates isomerizes to the trans cation. Simulations are consistent with a rate constant of 3.1 +/- 0.3 s(-1) for this isomerization process. Monitoring the reaction by in situ IR spectroscopy at low-temperature enables the identification of the nu(CO) bands of all four species ((cis,mer)(0); (cis,mer)(+); (trans)(0); (trans)(+)) in the resultant square reaction scheme that is operative under these thin layer electrolysis conditions. Additionally, 17-electron cis,fac-Mn(CO)(2)(eta(1)-dpm)(eta(2)-dpm)Br and its 18-electron (cis,fac)(0) counterpart, generated by a redox-induced catalytic isomerization reaction, are detected and characterized by IR spectroscopy (nu(CO)). Room-temperature bulk oxidative electrolysis experiments reveal that the trans cation, generated in bulk solution from the (cis,mer)(+) and (cis,fac)(+) isomers, slowly ejects bromide with a rate constant of 1.6 x 10(-3) s(-1) to form trans-Mn(CO)(2)(eta(2)-dpm)(2). The equivalent voltammetry in acetonitrile is complicated by an additional competing kinetic step which is attributed to reaction of this cation with the solvent. However, the major product formed upon oxidation at room temperature is still the trans cation. Less detailed studies on the oxidation of cis,mer-[Mn(CO)(2)(eta(1)-dpm)(eta(2)-dpm)Cl] only show significant differences under conditions of bulk electrolysis after trans-Mn(CO)(2)(eta(2)-dpm)(2) is formed via expulsion of Cl(-).
通过伏安法、恒电流电解法、原位和非原位光谱电化学法以及模拟技术，对顺式、反式 - [Mn(CO)(2)(η¹ - dpm)(η² - dpm)Br]（dpm = Ph₂PCH₂PPh₂），即 (顺式,反式)(0) ，在二氯甲烷（0.1 M Bu₄NPF₆）中的电化学氧化进行了研究。在20℃的伏安时间尺度上，中性的18电子顺式、反式Mn(I) 物种被氧化为相应的17电子阳离子，该阳离子在慢扫描速率下异构化为反式阳离子。模拟结果与该异构化过程的速率常数3.1 ± 0.3 s⁻¹ 一致。通过低温原位红外光谱监测反应，可以识别在这些薄层电解条件下运行的方形反应方案中所有四种物种（(顺式,反式)(0)；(顺式,反式)(+)；(反式)(0)；(反式)(+)）的ν(CO) 谱带。此外，通过氧化还原诱导的催化异构化反应生成的17电子顺式、面式 - Mn(CO)(2)(η¹ - dpm)(η² - dpm)Br 及其18电子 (顺式,面式)(0) 对应物，通过红外光谱（ν(CO)）进行了检测和表征。室温下的恒电流氧化电解实验表明，在本体溶液中由 (顺式,反式)(+) 和 (顺式,面式)(+) 异构体生成的反式阳离子，以1.6×10⁻³ s⁻¹ 的速率常数缓慢排出溴离子，形成反式 - Mn(CO)(2)(η² - dpm)₂。在乙腈中的等效伏安法因一个额外的竞争动力学步骤而变得复杂，该步骤归因于该阳离子与溶剂的反应。然而，室温下氧化形成的主要产物仍然是反式阳离子。对顺式、反式 - [Mn(CO)(2)(η¹ - dpm)(η² - dpm)Cl] 氧化的不太详细的研究仅表明，在通过排出Cl⁻ 形成反式 - Mn(CO)(2)(η² - dpm)₂ 后的本体电解条件下存在显著差异。
