Oxidative Stretching of Metal鈥揗etal Bonds to Their Limits
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- 作者：David W. Brogden ; Yevgeniya Turov ; Michael Nippe ; Giovanni Li Manni ; Elizabeth A. Hillard ; Rodolphe Cl茅rac ; Laura Gagliardi ; John F. Berry
- 刊名：Inorganic Chemistry
- 出版年：2014
- 出版时间：May 5, 2014
- 年：2014
- 卷：53
- 期：9
- 页码：4777-4790
- 全文大小：722K
- 年卷期：v.53,no.9(May 5, 2014)
- ISSN：1520-510X
文摘
Oxidation of quadruply bonded Cr2(dpa)4, Mo2(dpa)4, MoW(dpa)4, and W2(dpa)4 (dpa = 2,2鈥?dipyridylamido) with 2 equiv of silver(I) triflate or ferrocenium triflate results in the formation of the two-electron-oxidized products [Cr2(dpa)4]2+ (1), [Mo2(dpa)4]2+ (2), [MoW(dpa)4]2+ (3), and [W2(dpa)4]2+ (4). Additional two-electron oxidation and oxygen atom transfer by m-chloroperoxybenzoic acid results in the formation of the corresponding metal鈥搊xo compounds [Mo2O(dpa)4]2+ (5), [WMoO(dpa)4]2+ (6), and [W2O(dpa)4]2+ (7), which feature an unusual linear M路路路M鈮 structure. Crystallographic studies of the two-electron-oxidized products 2, 3, and 4, which have the appropriate number of orbitals and electrons to form metal鈥搈etal triple bonds, show bond distances much longer (by >0.5 脜) than those in established triply bonded compounds, but these compounds are nonetheless diamagnetic. In contrast, the Cr鈥揅r bond is completely severed in 1, and the resulting two isolated Cr3+ magnetic centers couple antiferromagnetically with J/kB= 鈭?08(3) K [鈭?5(2) cm鈥?], as determined by modeling of the temperature dependence of the magnetic susceptibility. Density functional theory (DFT) and multiconfigurational methods (CASSCF/CASPT2) provide support for 鈥渟tretched鈥?and weak metal鈥搈etal triple bonds in 2, 3, and 4. The metal鈥搈etal distances in the metal鈥搊xo compounds 5, 6, and 7 are elongated beyond the single-bond covalent radii of the metal atoms. DFT and CASSCF/CASPT2 calculations suggest that the metal atoms have minimal interaction; the electronic structure of these complexes is used to rationalize their multielectron redox reactivity.