Luff Martin S, Walther Luis, Finze Maik, Radius Udo
Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
Dalton Trans. 2024 Mar 19;53(12):5391-5400. doi: 10.1039/d4dt00231h.
A comprehensive study on the synthesis and characterization of NHC-ligated nickel(II) cyanoborates (CBs) is presented (NHC = N-heterocyclic carbene). Nickel(II) cyanoborates Ni[BH(CN)]·HO (Ib·HO), Ni[BH(CN)]·0.5HO (Ic·0.5HO), Ni[B(CN)]·HO (Id·HO) were reacted with selected NHCs of different steric size. The reaction of the nickel cyanoborates with small to medium-sized NHCs MeIm and iPrIm (RIm = 1,3-di-organyl-imidazolin-2-ylidene; RIm = 1,3-di-organyl-4,5-dimethyl-imidazolin-2-ylidene) afforded cyanoborate salts containing the rare homoleptic fourfold NHC-ligated nickel(II) cations [Ni(NHC)] (NHC = MeIm (1c-d), iPrIm (2c-d)) and cyanoborate counter-anions. Bulkier NHCs such as MesIm and DippIm afforded complexes -[Ni(NHC)(CB)] (-4b, -5c). For the combination of the cyanoborate anion [BH(CN)] and iPrIm the salt of the tris-NHC complex [Ni(iPrIm)(NC-BHCN)][BH(CN)] (3b) was isolated. Salt metathesis of NHC-ligated nickel(II) halides (Ni(NHC)X) (X = Cl, Br) with silver(I) and alkali metal cyanoborates were used to synthesize mono- and disubstituted coordination compounds of the type - or -[Ni(NHC)(CB)X] (-10c, -11c, -12b) and - or -[Ni(NHC)(CB)] (-13b, -14a-c, -14a-b, -15b, -5b). Further investigations reveal that NHC-ligated cyanoborate complexes can act as building blocks for coordination polymers, as observed for structurally characterized 1∞{-[Ni(MesIm)(μ-[NC-BH-CN])]·2Ag(μ-[BH(CN)])} (-5b·Ag). This study demonstrates the diverse character of cyanoborates in coordination chemistry as both, non-coordinating counter-anions, and weakly to medium coordinating anions forming novel transition metal complexes and salts. It provides evidence that a proper choice of cyanoborate and a proper choice of co-ligand can lead to a rich coordination chemistry of cyanoborate anions.
本文介绍了一项关于氮杂环卡宾（NHC）配位的氰基硼酸镍（II）（CBs）的合成与表征的综合研究（NHC = N-杂环卡宾）。氰基硼酸镍（II）Ni[BH(CN)]·HO（Ib·HO）、Ni[BH(CN)]·0.5HO（Ic·0.5HO）、Ni[B(CN)]·HO（Id·HO）与不同空间位阻大小的选定NHCs反应。氰基硼酸镍与中小尺寸的NHCs MeIm和iPrIm（RIm = 1,3-二有机基-咪唑啉-2-亚基；RIm = 1,3-二有机基-4,5-二甲基-咪唑啉-2-亚基）反应，得到了含有罕见的全同四配位NHC配位镍（II）阳离子[Ni(NHC)]（NHC = MeIm（1c-d），iPrIm（2c-d））和氰基硼酸根抗衡阴离子的氰基硼酸盐。体积更大的NHCs如MesIm和DippIm得到了配合物-[Ni(NHC)(CB)]（-4b，-5c）。对于氰基硼酸根阴离子[BH(CN)]和iPrIm的组合，分离出了三-NHC配合物[Ni(iPrIm)(NC-BHCN)][BH(CN)]（3b）的盐。NHC配位的镍（II）卤化物（Ni(NHC)X）（X = Cl，Br）与银（I）和碱金属氰基硼酸盐的盐复分解反应被用于合成-或-[Ni(NHC)(CB)X]（-10c，-11c，-12b）以及-或-[Ni(NHC)(CB)]（-13b，-14a-c，-14a-b，-15b，-5b）类型的单取代和双取代配位化合物。进一步的研究表明，NHC配位的氰基硼酸配合物可以作为配位聚合物的结构单元，如结构表征的1∞{-[Ni(MesIm)(μ-[NC-BH-CN])]·2Ag(μ-[BH(CN)])}（-5b·Ag）所示。这项研究证明了氰基硼酸盐在配位化学中的多样性，它既可以作为非配位抗衡阴离子，也可以作为弱到中等配位的阴离子，形成新型的过渡金属配合物和盐。它提供了证据，表明适当选择氰基硼酸盐和适当选择共配体可以导致氰基硼酸根阴离子丰富的配位化学。
