Cobalt(II)-containing ionic liquids were synthesized using N,N-dimethylformamide, N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMAc), pyridine-N-oxide (py-O), 1,10-phenanthroline (phen), ethylenediamine (en) and dimethylimidazolidinone (DMI) as ligands. The weakly coordinating bis(trifluoromethylsulfonyl)imide (Tf₂N⁻) was used as a counter anion. Several compounds had a melting temperature below 100 °C, and the compound [Co(DMAc)₆][Tf₂N]₂ was liquid at room temperature, with a viscosity of only 18 mPa s at 80 °C. Several compounds were recrystallized to give high quality single crystals and their crystal structures were determined. EXAFS measurements were performed on [Co(DMAc)₆][Tf₂N]₂ at different temperatures and it was observed that the [Co(DMAc)₆]²⁺ ion partially dissociated at higher temperatures, which explains the temperature-dependent color change (thermochromism). The electrochemical properties of the compounds with the lowest melting points were also investigated. Adherent, crack-free metallic cobalt layers could be electrodeposited from [Co(DMAc)₆][Tf₂N]₂, [Co(DMI)₆][Tf₂N]₂ and [Co(NMP)₆][Tf₂N]₂. From the first two, black deposits consisting of micrometer-sized needles were obtained, whereas the latter resulted in a dull grey cobalt layer consisting of micrometer-sized cobalt spheres. The Co(III)/Co(II) redox couple was not found to occur in any compound with an O-donor ligand, but the Co(III)/Co(II) redox couple was found to be quasi-reversible for [Co(phen)₃][Tf₂N]₂ dissolved in [BMP][Tf₂N].

中文翻译：

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钴（ii）液态金属盐，用于钴的高电流密度电沉积†

钴（II）的含离子性液体，使用合成Ñ，Ñ二甲基甲酰胺，Ñ甲基吡咯烷酮（NMP），二甲亚砜（DMSO），Ñ，Ñ二甲基乙酰胺（DMAc）中，吡啶Ñ氧化物（PY-O），1 1,10-菲咯啉（phen），乙二胺（en）和二甲基咪唑啉酮（DMI）作为配体。弱配位的双（三氟甲磺酰）亚胺（TF ₂ Ñ ^- ）作为抗衡阴离子。几种化合物的熔融温度低于100°C，化合物[Co（DMAc）₆ ] [Tf ₂ N] ₂室温下呈液态，在80°C下的粘度仅为18 mPa s。重结晶了几种化合物，得到了高质量的单晶，并确定了它们的晶体结构。在不同温度下对[Co（DMAc）₆ ] [Tf ₂ N] ₂进行EXAFS测量，观察到[Co（DMAc）₆ ] ²⁺离子在较高温度下部分解离，这解释了温度相关的颜色变化（热变色）。还研究了熔点最低的化合物的电化学性质。可以从[Co（DMAc）₆ ] [Tf ₂ N] ₂电沉积附着的，无裂纹的金属钴层，[Co（DMI）₆ ] [Tf ₂ N] ₂和[Co（NMP）₆ ] [Tf ₂ N] ₂。从前两个中获得了由微米尺寸的针组成的黑色沉积物，而后者形成了由微米尺寸的钴球组成的暗灰色钴层。没有发现Co（III）/ Co（II）的氧化还原对在任何具有O-供体配体的化合物中都发生，但是Co（III）/ Co（II）的氧化还原对被发现对[Co是准可逆的。 （phen）的₃ ] [TF ₂ N] ₂溶解在[BMP] [TF ₂ N]。