Monofunctionalized Cobaltocenium Compounds by Dediazoniation Reactions of Cobaltoceniumdiazonium Bis(hexafluorophosphate)

Monofunctionalized cobaltocenium salts are obtained for the first time from cobaltoceniumdiazonium bis­(hexafluorophosphate) with various nucleophiles via Sandmeyer-type and related reactions. For successful conversions, reaction conditions are quite critical: either standard solution chemistry in nitromethane or solvent-free ball milling proved necessary, depending on the type of reactant. By this synthetic approach valuable synthons such as iodocobaltocenium and azidocobaltocenium salts are accessible that open up new vistas in cobaltocenium chemistry. Spectroscopic characterization by NMR, IR, HRMS, and single-crystal structure analysis as well as the results of electrochemical studies are reported. Derivatives with two reversible reductions show the expected relation of the half-wave potentials with the Hammett substituent parameter σp of the respective substituent with a slightly larger slope for the first reduction. The carboxylic acid (reductive deprotonation of the −COOH functionality), the iodo (protodehalogenation), and the azido derivatives undergo irreversible subsequent reactions after primary reduction.本研究首次以重氮化二茂钴𬭩双六氟磷酸盐（cobaltoceniumdiazonium bis(hexafluorophosphate)）为起始原料，通过桑德迈尔型（Sandmeyer-type）及相关反应与各类亲核试剂反应，成功制备得到单官能团化二茂钴𬭩盐。反应的成功与否对条件要求极为严苛：依据反应物种类的不同，需分别采用硝基甲烷中的标准溶液相反应体系，或是无溶剂球磨（solvent-free ball milling）工艺。通过该合成策略，可获得碘代二茂钴𬭩、叠氮代二茂钴𬭩等具有高应用价值的合成子（synthons），为二茂钴𬭩化学领域开辟了全新的研究前景。本研究报道了所有目标产物的核磁共振（NMR）、红外（IR）、高分辨质谱（HRMS）光谱表征及单晶结构分析结果，同时附上电化学研究的相关数据。带有两处可逆还原峰的衍生物，其半波电位与对应取代基的哈米特取代基参数σ_p（Hammett substituent parameter σ_p）呈现预期的线性关联，且首次还原过程的斜率略大于第二次还原。其中，羧酸衍生物（经-COOH官能团的还原脱质子反应）、碘代衍生物（经脱卤质子化反应）以及叠氮衍生物在初次还原后，均会发生不可逆的后续反应。