Institut für Anorganische Chemie, Georg-August-Universität , Tammannstraße 4, 37077 Göttingen, Germany.
J Am Chem Soc. 2014 Feb 5;136(5):1770-3. doi: 10.1021/ja4123285. Epub 2014 Jan 24.
(Me2-cAAC:)2Co2 (2, where Me2-cAAC: = cyclic alkyl amino carbene, :C(CH2)(CMe2)2N-2,6-iPr2C6H3)) was synthesized via the reduction of precursor (Me2-cAAC:Co(II)(μ-Cl)Cl)2 (1) with KC8. 2 contains two cobalt atoms in the formal oxidation state zero. Magnetic measurement revealed that 2 has a singlet spin ground state S = 0. The cyclic voltammogram of 2 exhibits both one-electron oxidation and reduction, indicating the possible synthesis of stable species containing 2(•-) and 2(•+) ions. The latter was synthesized via reduction of 1 with required equivalents of KC8 and characterized as (Me2-cAAC:)2Co2OTf(-) (2(•+)OTf(-)). Electron paramagnetic resonance spectroscopy of 2(•+) reveals the coupling of the electron spin with 2 equiv (59)Co isotopes, leading to a (Co(0.5))2 state. The experimental Co1-Co2 bond distances are 2.6550(6) and 2.4610(6) Å for 2 and 2(•+)OTf(-), respectively. Theoretical investigation revealed that both 2 and 2(•+)OTf(-) possess a Co-Co bond with an average value of 2.585 Å. A slight increase of the Co-Co bond length in 2 is more likely to be caused by the strong π-accepting property of cAAC. 2(•+) is only 0.8 kcal/mol higher in energy than the energy minimum. The shortening of the Co-Co bond of 2(•+) is caused by intermolecular interactions.
(Me2-cAAC:)2Co2 (2，其中 Me2-cAAC: = 环状烷基氨基卡宾，:C(CH2)(CMe2)2N-2,6-iPr2C6H3)) 通过用 KC8 还原前体(Me2-cAAC:Co(II)(μ-Cl)Cl)2 (1) 合成。2 中两个钴原子处于形式氧化态零。磁性测量表明 2 具有单重自旋基态 S = 0。2 的循环伏安图显示出一个电子的氧化和还原，表明可能合成了含有 2(•-)和 2(•+)离子的稳定物种。后者通过用所需当量的 KC8 还原 1 并作为 (Me2-cAAC:)2Co2OTf(-) (2(•+)OTf(-)) 来表征。2(•+)的电子顺磁共振光谱显示电子自旋与 2 个当量 (59)Co 同位素的耦合，导致 (Co(0.5))2 态。2(•+) 的实验 Co1-Co2 键距离分别为 2.6550(6) 和 2.4610(6) Å，用于 2 和 2(•+)OTf(-)。理论研究表明，2 和 2(•+)OTf(-) 都具有 Co-Co 键，平均键长为 2.585 Å。在 2 中 Co-Co 键长的轻微增加更可能是由于 cAAC 的强 π-接受性质。2(•+) 的能量仅比能量最低点高 0.8 kcal/mol。2(•+) 的 Co-Co 键缩短是由分子间相互作用引起的。
