New Complexes of Chromium(III) Containing Organic 蟺-Radical Ligands: An Experimental and Density Functional Theory Study
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- 作者：Mei Wang ; Jason England ; Thomas Weyherm眉ller ; Swarna-Latha Kokatam ; Christopher J. Pollock ; Serena DeBeer ; Jingmei Shen ; Glenn P.A. Yap ; Klaus H. Theopold ; Karl Wieghardt
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：April 15, 2013
- 年：2013
- 卷：52
- 期：8
- 页码：4472-4487
- 全文大小：847K
- 年卷期：v.52,no.8(April 15, 2013)
- ISSN：1520-510X
文摘
The electronic structures of a series of chromium complexes 1鈥?b>7 have been experimentally investigated using a combination of X-ray crystallography, magneto- and electrochemistry, and Cr K-edge X-ray absorption and UV鈥搗is spectroscopies. Reaction of the dimer [CrII2(渭-CH3CO2)4]0 with 2,2鈥?bipyridine (bpy0) produced the complex [CrIII(bpy0)(bpy鈥?/sup>)(CH3CO2)2]0 (S = 1) (1), but in the presence of isopropylamine (iPrNH2) [CrIII(bpy鈥?/sup>)(iPrNH2)2(CH3CO2)2]0 (S = 1) (2) was obtained. Both 1 and 2 contain a CrIII ion and a single (bpy鈥?/sup>)1鈥?/sup> ligand, so are not low-spin CrII species. One-electron oxidation of 1 and 2 yielded [CrIII(bpy0)2(CH3CO2)2]PF6 (S = 3/2) (3) in both cases. In addition, the new neutral species [CrIII(DAD鈥?/sup>)3]0 (S = 0) (4) and [CrIII(CF3AP鈥?/sup>)3]0 (S = 0) (5) have been synthesized. Both complexes contain three 蟺-radical anion ligands, which derive from one electron reduction of 1,4-bis(cyclohexyl)-1,4-diaza-1,3-butadiene and one electron oxidation of 2-(2-trifluoromethyl)-anilino-4,6-di-tert-butylphenolate, respectively. Intramolecular antiferromagnetic coupling to d3 CrIII gives the observed singlet ground states. Reaction of [CrII(CH3CN)6](PF6)2 with 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (PDI0) under anaerobic conditions affords dark brown microcrystals of [CrIII(PDI0)(PDI鈥?/sup>)](PF6)2 (S = 1) (6). This complex is shown to be a member of the electron transfer series [CrIII(PDI)2]3+/2+/1+/0, in which all one-electron transfer processes are ligand-based. By X-ray crystallography, it was shown that 6 possesses a localized electronic structure, such that one ligand is neutral (PDI0) and the other is a 蟺-radical monoanion (PDI鈥?/sup>)1鈥?/sup>. Again, it should be highlighted that 6 is not a CrII species. Lastly, the structure of [CrIII(Mebpy鈥?/sup>)3]0 (S = 0) (7, Mebpy = 4,4鈥?dimethyl-2,2鈥?bipyridine) has been established by high resolution X-ray crystallography and clearly shows that three (Mebpy鈥?/sup>)1鈥?/sup> radical anions are present. To further validate our electronic structure assignments, complexes 1鈥?b>6 were investigated computationally using density functional theory (DFT) and found in all cases to contain a CrIII ion. This oxidation state assignment was experimentally confirmed for complexes 2, 4, 5, and 6 by Cr K-edge X-ray absorption spectroscopy.