Mixed-Valent Dicobalt and Iron鈥揅obalt Complexes with High-Spin Configurations and Short Metal鈥揗etal Bonds

详细信息    查看全文

• 作者：Christopher M. Zall ; Laura J. Clouston ; Victor G. Young ; Jr. ; Keying Ding ; Hyun Jung Kim ; Danylo Zherebetskyy ; Yu-Sheng Chen ; Eckhard Bill ; Laura Gagliardi ; Connie C. Lu
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：August 19, 2013
• 年：2013
• 卷：52
• 期：16
• 页码：9216-9228
• 全文大小：581K
• 年卷期：v.52,no.16(August 19, 2013)
• ISSN：1520-510X

文摘

Cobalt鈥揷obalt and iron鈥揷obalt bonds are investigated in coordination complexes with formally mixed-valent [M₂]³⁺ cores. The trigonal dicobalt tris(diphenylformamidinate) compound, Co₂(DPhF)₃, which was previously reported by Cotton, Murillo, and co-workers (Inorg. Chim. Acta 1996, 249, 9), is shown to have an energetically isolated, high-spin sextet ground-state by magnetic susceptibility and electron paramagnetic resonance (EPR) spectroscopy. A new tris(amidinato)amine ligand platform is introduced. By tethering three amidinate donors to an apical amine, this platform offers two distinct metal-binding sites. Using the phenyl-substituted variant (abbreviated as L^Ph), the isolation of a dicobalt homobimetallic and an iron鈥揷obalt heterobimetallic are demonstrated. The new [Co₂]³⁺ and [FeCo]³⁺ cores have high-spin sextet and septet ground states, respectively. Their solid-state structures reveal short metal鈥搈etal bond distances of 2.29 脜 for Co鈥揅o and 2.18 脜 for Fe鈥揅o; the latter is the shortest distance for an iron鈥揷obalt bond to date. To assign the positions of iron and cobalt atoms as well as to determine if Fe/Co mixing is occurring, X-ray anomalous scattering experiments were performed, spanning the Fe and Co absorption energies. These studies show only a minor amount of metal-site mixing in this complex, and that FeCoL^Ph is more precisely described as (Fe_0.94(1)Co_0.06(1))(Co_0.95(1)Fe_0.05(1))L^Ph. The iron鈥揷obalt heterobimetallic has been further characterized by M枚ssbauer spectroscopy. Its isomer shift of 0.65 mm/s and quadrupole splitting of 0.64 mm/s are comparable to the related diiron complex, Fe₂(DPhF)₃. On the basis of spectroscopic data and theoretical calculations, it is proposed that the formal [M₂]³⁺ cores are fully delocalized.