Effect of Pyramidalization of the M2(SR)2 Center: The Case of (C5H5)2Ni2(SR)2
Effect of Pyramidalization of the M2(SR)2 Center: The Case of (C5H5)2Ni2(SR)2
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DOI：
10.1021/acs.organomet.6b00068
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发表时间：
2016-03-14
期刊：
影响因子：
2.8
通讯作者：
Zampella, Giuseppe
中科院分区：
文献类型：
--
作者：
Chambers, Geoffrey M.;Rauchfuss, Thomas B.;Zampella, Giuseppe
简单的硫醇盐与螯合二硫醇盐对MM键合，氧化还原电位和合成结果的影响进行了实验和计算。二茂镍（Cp 2Ni）与简单硫醇反应生成抗磁性的Cp 2Ni 2（SR）（2），具有平面的Ni 2S 2核和长的Ni-Ni距离。乙烷-和丙烷二硫醇（edtH（2）和pdtH（2），分别），而得到二，三，和五镍配合物，与非平面Ni 2S 2核心。36 e Cp 2Ni 2（pdt）（1（pdt））采用对称蝶形Ni 2S 2结构。变温NMR谱表明1（pdt）具有与抗磁性基态平衡的可热接近的三重态（Δ G = 2.65（5）kcal/mol）。DFT计算表明，单重态三重态能隙对Ni 2S 2核的非平面性高度敏感。计算进一步揭示，只有高自旋形式的1（pdt）功能NiNi键，这是前所未有的。Cp 2Ni 3（pdt）（2）（2（pdt））衍生自1（pdt），结晶为顺式和反式异构体，两者都具有中心Ni（pdt）（2）（2）单元，其S，S-螯合到两个CpNi+中心。Cp 2Ni与1，2-乙二硫醇（H（2）edt）和1，2-苯二硫醇（bdtH（2））反应，只生成三镍物种2（edt）和2（bdt），它们在结构上类似于cis-2（pdt）。2（edt）的溶液是不稳定的，沉积Cp 2Ni 5（edt）（4）（3（edt））的晶体。循环伏安研究表明，Ni-2物种容易氧化，生成混合价阳离子[1（pdt）]（+）和[1（edt）]（+）。晶体学和EPR分析表明，这些阳离子是离域的混合价态Ni（II）Ni（III）物种。Cp 2Ni 2（SEt）（2）具有平面Ni 2S 2核，氧化得到混合价阳离子，显示在[1（pdt）]（0/+）和[1（edt）]（0/+）中观察到的金字塔状Ni 2S 2核。虽然不是由Cp_2Ni/H（2）edt反应得到的，但中性配合物1（edt）是由[1（edt）]（+）还原得到的。变温NMR测量和DFT计算表明，三重态进一步稳定在这个高度异构化的物种。
The effects of simple thiolates vs chelating dithiolates on MM bonding, redox potentials, and synthetic outcomes have been probed experimentally and computationally. Nickelocene (Cp2Ni) has long been known to react with simple thiols to give diamagnetic Cp2Ni2(SR)(2) with planar Ni2S2 cores and long Ni-- -Ni distances. Ethane- and propanedithiol (edtH(2) and pdtH(2), respectively) instead give di-, tri-, and pentanickel complexes, with nonplanar Ni2S2 cores. The 36e Cp2Ni2(pdt) (1(pdt)) adopts a symmetrical butterfly Ni2S2 structure. Variable-temperature NMR spectra indicate that 1(pdt) possesses a thermally accessible triplet state (Delta G = 2.65(5) kcal/mol) in equilibrium with a diamagnetic ground state. DFT calculations indicate that the singlettriplet gap is highly sensitive to the nonplanarity of the Ni2S2 core. The calculations further reveal that only the high-spin form of 1(pdt) features NiNi bonding, which is unprecedented. Cp2Ni3(pdt)(2) (2(pdt)), which derives from 1(pdt), crystallized as cis and trans isomers, both with a central Ni(pdt)(2)(2) unit that is S,S-chelated to two CpNi+ centers. Reaction of Cp2Ni with 1,2-ethanedithiol (H(2)edt) and 1,2-benzenedithiol (bdtH(2)) exclusively gave the trinickel species 2(edt) and 2(bdt), which are structurally analogous to cis-2(pdt). Solutions of 2(edt) are unstable, depositing crystals of Cp2Ni5(edt)(4) (3(edt)). Cyclic voltammetric studies show that the Ni-2 species oxidize readily to give the mixed-valence cations [1(pdt)](+) and [1(edt)](+). Crystallographic and EPR analyses indicate that these cations are delocalized mixed-valence Ni(II)Ni(III) species. Oxidation of Cp2Ni2(SEt)(2), which features a planar Ni2S2 core, afforded a mixed-valence cation, showing the pyramidal Ni2S2 core observed in [1(pdt)](0/+) and [1(edt)](0/+). Although not obtained from the Cp2Ni/H(2)edt reaction, the neutral complex 1(edt) was obtained by reduction of [1(edt)](+). Variable-temperature NMR measurements and DFT calculations indicate that the triplet is further stabilized in this highly pyramidalized species.