Neururer Florian R, Huter Konstantin, Seidl Michael, Hohloch Stephan
Faculty of Chemistry, Institute of Inorganic, General and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
ACS Org Inorg Au. 2022 Dec 5;3(1):59-71. doi: 10.1021/acsorginorgau.2c00028. eCollection 2023 Feb 1.
We report the facile synthesis of a rare niobium(V) imido NHC complex with a dianionic OCO-pincer benzimidazolylidene ligand ( ) with the general formula . We achieved this by deprotonation of the corresponding azolium salt and subsequent reaction with . The pyridine ligand in can be removed by the addition of B(CF) as a strong Lewis acid leading to the formation of the pyridine-free complex . In contrast to similar vanadium(V) complexes, complex was found to be a good precursor for various salt metathesis reactions, yielding a series of chalcogenido and pnictogenido complexes with the general formula (E = O (), S (), NH (), and PH ()). Furthermore, complex can be converted to alkyl complex () with 1 equiv of neosilyl lithium as a transmetallation agent. Addition of a second equivalent yields a new trianionic supporting ligand on the niobium center () in which the benzimidazolylidene ligand is alkylated at the former carbene carbon atom. The latter is an interesting chemically "noninnocent" feature of the benzimidazolylidene ligand potentially useful in catalysis and atom transfer reactions. Addition of mesityl lithium to gives the pyridine-free aryl complex , which is stable toward "overarylation" by an additional equivalent of mesityl lithium. Electrochemical investigation revealed that complexes and are inert toward reduction in dichloromethane but show two irreversible reduction processes in tetrahydrofuran as a solvent. However, using standard reduction agents, , KC, K-mirror, and Na/Napht, no reduced products could be isolated. All complexes have been thoroughly studied by various techniques, including H-, C{H}-, and H-N HMBC NMR spectroscopy, IR spectroscopy, and X-ray diffraction analysis.
我们报道了一种罕见的铌（V）亚胺基 NHC 配合物的简便合成方法，该配合物带有双阴离子 OCO-钳形苯并咪唑亚基配体（ ），通式为 。我们通过使相应的唑鎓盐 去质子化，随后与 反应来实现这一合成。 中的吡啶配体可通过加入强路易斯酸 B(CF) 除去，从而形成无吡啶配合物 。与类似的钒（V）配合物不同，发现配合物 是各种盐复分解反应的良好前体，可生成一系列通式为 （E = O （）、S （）、NH （）和 PH （））的硫属化物和氮族化物配合物。此外，配合物 可用 1 当量的新硅基锂作为金属转移剂转化为烷基配合物（）。加入第二当量会在铌中心（）上产生一种新的三阴离子支撑配体，其中苯并咪唑亚基配体在前卡宾碳原子处被烷基化。后者是苯并咪唑亚基配体一个有趣的化学“非无辜”特征，可能在催化和原子转移反应中有用。向 中加入均三甲苯基锂得到无吡啶芳基配合物 ，它对再加入当量的均三甲苯基锂进行“过度芳基化”具有稳定性。电化学研究表明，配合物 和 在二氯甲烷中对还原呈惰性，但在四氢呋喃作为溶剂时显示出两个不可逆的还原过程。然而，使用标准还原剂 、KC、K 镜和 Na/萘，无法分离出还原产物。所有配合物都通过各种技术进行了深入研究，包括 H-、C{H}-和 H-N HMBC NMR 光谱、IR 光谱和 X 射线衍射分析。
