六重鍵

六重鍵（英語：Sextuple Bond），是指化學中，由6對價電子組成的共價鍵。

六重鍵的鍵級為6，含有六重鍵的化合物僅有雙原子分子的 ${\ce {Mo2}}$ 和 ${\ce {W2}}$ ，而它們僅在非常低的溫度下存在於氣相。

儘管雙原子的 ${\ce {Cr2}}$ 和 ${\ce {U2}}$ 也有名義上的6對價電子組成的鍵，但根據量子化學的計算，它們的有效鍵級小於5，可能是五重鍵。^[1]

有很強的證據顯示，元素週期表中任何兩個元素之間不可能形成鍵級超過六的化學鍵^[2]。

氣相中的 ${\ce {Mo2}}$ 的觀測必須在很低的溫度（7K），使用雷射蒸發技術，用近紅外光譜或紫外光譜進行觀測。^[3]

科學界期望可以於 ${\ce {Mo2}}$ 發現到與 ${\ce {Cr2}}$ 觀察結果類似的一對雙自由基^[4]。

更高的鍵級將會反映在更短的鍵長上，僅有1.94 Å。^{[來源請求]}

參見

鉬（ ${\ce {Mo}}$ ）
鎢（ ${\ce {W}}$ ）
鉻（ ${\ce {Cr}}$ ）
鈾（ ${\ce {U}}$ ）
價電子

參考文獻

^ Roos, Björn O.; Borin, Antonio C.; Gagliardi, Laura. Reaching the Maximum Multiplicity of the Covalent Chemical Bond. Angewandte Chemie. 2007-02-19, 119 (9): 1491–1494 [2018-01-30]. ISSN 1521-3757. doi:10.1002/ange.200603600. （原始內容存檔於2018-01-30）（英語）.
^ Roos, Björn O.; Antonio C. Borin, and Laura Gagliardi. Reaching the Maximum Multiplicity of the Covalent Chemical Bond. Angewandte Chemie International Edition. 2007. doi:10.1002/anie.200603600.
^ D. Kraus, M. Lorenz and V. E. Bondybey. On the dimers of the VIB group: a new NIR electronic state of Mo₂. PhysChemComm. 2001, 4: 44 – 48. doi:10.1039/b104063b.
^ Gabriel Merino, Kelling J. Donald, Jason S. D』Acchioli, and Roald Hoffmann. The Many Ways To Have a Quintuple Bond. J. Am. Chem. Soc. 2007, 129 (49): 15295 –15302. doi:10.1021/ja075454b.

擴展閱讀

Bruce E. Bursten; F. Albert Cotton; Michael B. Hall. Dimolybdenum: nature of the sextuple bond. Journal of the American Chemical Society. 1980, 102 (20): 6348. doi:10.1021/ja00540a034.
Borin, A; Gobbo, João Paulo; Roos, Björn O. A theoretical study of the binding and electronic spectrum of the Mo2 molecule. Chemical Physics. 2008, 343 (2–3): 210. doi:10.1016/j.chemphys.2007.05.028.
Marvin M. Goodgame; William A. Goddard I I I. The "sextuple" bond of chromium dimer. The Journal of Physical Chemistry. 1981, 85 (3): 215. doi:10.1021/j150603a001.
Chisholm, Mh. Metal to metal multiple bonds in ordered assemblies (Free full text). Proceedings of the National Academy of Sciences of the United States of America. Feb 2007, 104 (8): 2563–70 [2012-08-12]. PMC 1815223  . PMID 17299047. doi:10.1073/pnas.0610364104. （原始內容存檔於2020-01-24）.
Norman, Joe G., Jr.; Ryan, P. Barry. Metal-metal bond energies in diatomic molybdenum, octachloromolybdate (Mo2Cl84-), and molybdenum formate (Mo2(O2CH)4). Journal of Computational Chemistry. 1980, 1 (1): 59–63. doi:10.1002/jcc.540010107.
Atha, P. M.; Hillier, I. H.; Guest, M. F. Electron correlation and the nature of the sextuple bond in the dimolybdenum molecule. Chemical Physics Letters. 1980, 75 (1): 84–86. doi:10.1016/0009-2614(80)80469-6.
Wood, Carol; Doran, Mark; Hillier, Ian H.; Guest, Martyn F. Theoretical study of the electronic structure of the transition metal dimers, discandium, dichromium, dimolybdenum, and dinickel. Faraday Symp. R. Soc. Chem. 1980, 14 (Diatomic Met. Met. Clusters): 159–169. doi:10.1039/fs9801400159.

[1] Roos, Björn O.; Borin, Antonio C.; Gagliardi, Laura. Reaching the Maximum Multiplicity of the Covalent Chemical Bond. Angewandte Chemie. 2007-02-19, 119 (9): 1491–1494 [2018-01-30]. ISSN 1521-3757. doi:10.1002/ange.200603600. （原始內容存檔於2018-01-30）（英語）.

[2] Roos, Björn O.; Antonio C. Borin, and Laura Gagliardi. Reaching the Maximum Multiplicity of the Covalent Chemical Bond. Angewandte Chemie International Edition. 2007. doi:10.1002/anie.200603600.

[3] D. Kraus, M. Lorenz and V. E. Bondybey. On the dimers of the VIB group: a new NIR electronic state of Mo₂. PhysChemComm. 2001, 4: 44 – 48. doi:10.1039/b104063b.

[4] Gabriel Merino, Kelling J. Donald, Jason S. D』Acchioli, and Roald Hoffmann. The Many Ways To Have a Quintuple Bond. J. Am. Chem. Soc. 2007, 129 (49): 15295 –15302. doi:10.1021/ja075454b.

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