Role of the Metal in the Bonding and Properties of Bimetallic Complexes Involving Manganese, Iron, and Cobalt

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• 作者：Stephen J. Tereniak ; Rebecca K. Carlson ; Laura J. Clouston ; Victor G. Young ; Jr. ; Eckhard Bill ; Rémi Maurice ; Yu-Sheng Chen ; Hyun Jung Kim ; Laura Gagliardi ; Connie C. Lu
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：February 5, 2014
• 年：2014
• 卷：136
• 期：5
• 页码：1842-1855
• 全文大小：613K
• ISSN：1520-5126

文摘

A multidentate ligand platform is introduced that enables the isolation of both homo- and heterobimetallic complexes of divalent first-row transition metal ions such as Mn(II), Fe(II), and Co(II). By means of a two-step metalation strategy, five bimetallic coordination complexes were synthesized with the general formula M₁M₂Cl(py₃tren), where py₃tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. The metal鈥搈etal pairings include dicobalt (1), cobalt鈥搃ron (2), cobalt鈥搈anganese (3), diiron (4), and iron鈥搈anganese (5). The bimetallic complexes have been investigated by X-ray diffraction and X-ray anomalous scattering studies, cyclic voltammetry, magnetometry, M枚ssbauer spectroscopy, UV鈥搗is鈥揘IR spectroscopy, NMR spectroscopy, combustion analyses, inductively coupled plasma optical emission spectrometry, and ab initio quantum chemical methods. Only the diiron chloride complex in this series contains a metal鈥搈etal single bond (2.29 脜). The others show weak metal鈥搈etal interactions (2.49 to 2.53 脜). The diiron complex is also distinct with a septet ground state, while the other bimetallic species have much lower spin states from S = 0 to S = 1. We propose that the diiron system has delocalized metal鈥搈etal bonding electrons, which seems to correlate with a short metal鈥搈etal bond and a higher spin state. Multiconfigurational wave function calculations revealed that, indeed, the metal鈥搈etal bonding orbitals in the diiron complex are much more delocalized than those of the dicobalt analogue.