Homoleptic Organocobalt(III) Compounds with Intermediate Spin

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• 作者：M. Angeles Garc铆a-Monforte ; Irene Ara ; Antonio Mart铆n ; Babil Menj贸n ; Milagros Tom谩s ; Pablo J. Alonso ; Ana B. Arauzo ; Jes煤s I. Mart铆nez ; Conrado Rillo
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：December 1, 2014
• 年：2014
• 卷：53
• 期：23
• 页码：12384-12395
• 全文大小：570K
• ISSN：1520-510X

文摘

Homoleptic organocobalt(III) compounds with formula [NBu₄][Co^III(C₆X₅)₄] [X = F (3), Cl (4)] were obtained in reasonable yields by chemical oxidation of the corresponding divalent species [NBu₄]₂[Co^II(C₆X₅)₄] [X = F (1), Cl (2)]. The [Co^III(C₆X₅)₄]^{鈭?/sup>/[CoII(C₆X₅)₄]2鈥?/sup> couples are electrochemically related by quasi-reversible, one-electron exchange processes at moderate potential: E_1/2 = 鈭?.29 (X = F) and 鈭?.36 V (X = Cl) versus saturated calomel electrode. The [CoIII(C₆X₅)₄]鈭?/sup> anions in salts 3 and 4 show an unusual square-planar geometry as established by single-crystal X-ray diffraction methods. According to their stereochemistry, these CoIII derivatives (d6) are paramagnetic non-Kramers systems with a large zero-field splitting contribution and no observable electron paramagnetic resonance (EPR) spectrum. The thermal dependence of their magnetic susceptibilities can be explained in terms of a spin-Hamiltonian formalism with S = 1 ground state (intermediate spin) and substantial spin鈥搊rbit contribution. The magnetic properties of the square-planar d7 parent species [NBu₄]₂[CoII(C₆X₅)₄] were also thoroughly studied both at microscopic (EPR) and macroscopic levels (alternating current and direct current magnetization measurements). They behave as S = 1/2 (low spin) systems with mainly (d_z2)1 electron configuration and a certain degree of s-orbital admixture that has been quantified. The electronic structures of all four open-shell [Co(C₆X₅)₄]q鈭?/sup> compounds (q = 1, 2) accounting for their respective magnetic properties are based on a common orbital energy-level diagram.}