Chemical and Electrochemical Properties of [Cp*Rh] Complexes Supported by a Hybrid Phosphine-Imine Ligand
Chemical and Electrochemical Properties of [Cp*Rh] Complexes Supported by a Hybrid Phosphine-Imine Ligand
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DOI：
10.1021/acs.organomet.8b00551
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发表时间：
2019-03-25
期刊：
影响因子：
2.8
通讯作者：
Blakemore, James D.
中科院分区：
文献类型：
--
作者：
Hopkins, Julie A.;Lionetti, Davide;Blakemore, James D.
合成并表征了一系列含有κ（2）-[P，N]-8-（二苯基膦基）喹啉（PQN）配体的[Cp*Rh]配合物（Cp* = eta（5）-pentamethylamine）.铑（III）形式的化学或电化学还原产生可分离的铑（I）络合物;该铑（I）络合物与一系列有机酸反应以产生以eta（5）模式带有[Cp*]和以预期的kappa（2）模式带有[PQN]的氢化铑（III）。从X射线衍射研究这三种化合物的固态结构揭示了整个系列的配体内键距只有很小的变化，这表明与这些化合物的相互转化相关的氧化还原事件主要是金属为中心的。循环伏安数据表明，氯化铑（III）配合物在-1.19 V（相对于二茂铁/二茂铁）处发生双电子还原，而类似溶剂的铑（III）乙腈配合物发生两次连续的单电子还原。氢化铑（III）在-1.75V附近相对于二茂铁/二茂铁发生不可逆的配体中心还原。单独或在添加三乙基铵作为质子源的存在下进行该还原仅导致适度的H-2产率，如本体电解和化学还原实验所示。这些结果进行了讨论的背景下，最近的工作与[Cp*Rh]配合物轴承更对称的2，2 '-联吡啶和二膦配体。
A series of [Cp*Rh] complexes (Cp* = eta(5)-pentamethylcyclopentadienyl) bearing the kappa(2)-[P,N]-8-(diphenylphosphino)quinoline (PQN) ligand have been prepared and characterized. Chemical or electrochemical reduction of the rhodium(III) form generates an isolable rhodium(I) complex; this rhodium(I) complex reacts with a range of organic acids to yield a rhodium(III) hydride bearing [Cp*] in the eta(5) mode and [PQN] in the expected kappa(2) mode. Solid-state structures of these three compounds from X-ray diffraction studies reveal only small changes in the intraligand bond distances across the series, suggesting the redox events associated with interconversion of these compounds are primarily metal centered. Cyclic voltammetry data show that the rhodium(III) chloride complex undergoes a two-electron reduction at -1.19 V vs ferrocenium/ferrocene, whereas the analogous solvento rhodium(III) acetonitrile complex undergoes two sequential one-electron reductions. The rhodium(III) hydride undergoes an irreversible, ligand-centered reduction near -1.75 V vs ferrocenium/ferrocene. Carrying out this reduction alone or in the presence of added of triethylammonium as a source of protons results in only modest yields of H-2, as shown by bulk electrolyses and chemical reduction experiments. These results are discussed in the context of recent work with [Cp*Rh] complexes bearing more symmetric 2,2'-bipyridyl and diphosphine ligands.