Menia Daniel, Pittracher Michael, Kopacka Holger, Wurst Klaus, Neururer Florian R, Leitner Daniel, Hohloch Stephan, Podewitz Maren, Bildstein Benno
Institut für Allgemeine, Anorganische und Theoretische Chemie, Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
Institute of Materials Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
Organometallics. 2023 Feb 21;42(5):377-383. doi: 10.1021/acs.organomet.2c00613. eCollection 2023 Mar 13.
Cobaltocenium carbaldehyde (formylcobaltocenium) hexafluoridophosphate, a long sought-after functionalized cobaltocenium salt, is accessible from cobaltocenium carboxylic acid by a three-step synthetic sequence involving (i) chlorination to the acid chloride, (ii) copper-borohydride reduction to the hydroxymethyl derivative, and (iii) Dess-Martin oxidation to the title compound. Due to the strongly electron-withdrawing cationic cobaltocenium moiety, no standard aldehyde reactivity is observed. Instead, nucleophilic addition followed by haloform-type cleavage prevails, thereby ruling out common useful aldehyde derivatization. One-electron reduction of cobaltocenium carbaldehyde hexafluoridophosphate affords the deep-blue, isolable cobaltocene carbaldehyde 19-valence-electron radical whose spin density is located fully at cobalt and not at the formyl carbon atom. H/C NMR, IR, EPR spectroscopy, high-resolution mass spectrometry, cyclic voltammetry, single crystal structure analysis (XRD), and density functional theory are applied to characterize these unusual formyl-cobaltocenium/cobaltocene compounds.
六氟磷酸羰基钴茂（甲酰基钴茂），一种长期以来备受关注的官能化钴茂盐，可通过三步合成序列从钴茂羧酸制得，该序列包括：（i）氯化为酰氯，（ii）用硼氢化铜还原为羟甲基衍生物，以及（iii）用戴斯-马丁氧化剂氧化为目标化合物。由于阳离子钴茂部分具有强吸电子性，未观察到标准的醛反应活性。相反，亲核加成随后是卤仿型裂解占主导，从而排除了常见的有用醛衍生化反应。六氟磷酸羰基钴茂的单电子还原得到深蓝色、可分离的钴茂甲醛19价电子自由基，其自旋密度完全位于钴上而非甲酰基碳原子上。应用氢/碳核磁共振、红外光谱、电子顺磁共振光谱、高分辨率质谱、循环伏安法、单晶结构分析（X射线衍射）和密度泛函理论来表征这些不寻常的甲酰基钴茂/钴茂化合物。
