五重键

五重键（英語：Quintuple Bond），是指無機化學中，原子之間有5對價電子組成的共價鍵。

簡介

${\ce {[CrC6H3-2,6-\{C6H3-2,6-(CHMe2)2\}2]2}}$ 的結構式

五重键很罕见，直到2005年才从一个二铬化合物中发现，仅能在含鉻、鉬、鎢的化合物中发现。例如： ${\ce {[Mo2Cl8]^4-}}$ 和 ${\ce {[W2Cl8]^2-}}$ 。

在一个五重键中，两个金属原子间共有10个电子参与了成键，分布为：σ²π⁴δ⁴。

在某些化合物中，由于配体的促进作用，连接了两个金属中心并减少了原子间距离。

相反地， ${\ce {[CrC6H3-2,6-\{C6H3-2,6-(CHMe2)2\}2]2}}$ 「2,6-[(2,6-二異丙基)苯基]苯基」配體，或简单的三联苯配体均可以使一个拥有五重键的铬二聚物稳定，而这些化合物在200℃才会分解。^[1]^[2]

2005年，根据计算化学，化学家假设出一个存在五重键的双铀化合物 ${\ce {U2}}$ ^[3]^[4]，尽管双铀化合物很罕见，但确实存在诸如 ${\ce {[U2Cl8]^2-}}$ 的离子。

化学家^[谁？]陆续用多参考从头计算和密度泛函理论分析了铬-铬五重键。^[5]

^[何时？]研究阐明了三联苯配体在其中扮演的作用：

侧面的芳基和铬原子的相互作用十分微弱，仅能微量的弱化五重键。^[6]

在2007年，发表的一个理论研究确定五重键的RMMR化合物存在两个全局最小能量值：

其中之一是一个trans-弯折构型；而另外一个很令人惊讶，尽管也是trans-弯折构型，但R基团却在一个桥头的位置。^[7]

在2007年，在一个含有五重铬-铬键的化合物中发现了有记载以来最短的金属-金属键(1.8028 Å)。^[8]

拓展連結

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

参考文献

^ Quintuple Bond Makes Its Debut First stable molecule with fivefold metal-metal bonding is synthesized Steve Ritter Chemical & Engineering News September 26, 2005 Volume 83, Number 39 Article （页面存档备份，存于互联网档案馆）
^ Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers Tailuan Nguyen, Andrew D. Sutton, Marcin Brynda, James C. Fettinger, Gary J. Long, and Philip P. Power Published online September 22 2005; 10.1126/science.1116789 Support info （页面存档备份，存于互联网档案馆）
^ Quantum chemical calculations show that the uranium molecule U₂ has a quintuple bond Laura Gagliardi, Björn O. Roos Nature 433, 848-851 24 February 2005 Abstract （页面存档备份，存于互联网档案馆）
^ New look for chemical bonds Belle Dumé 23 February 2005 PhysicsWeb Article （页面存档备份，存于互联网档案馆）
^ Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans-Bent versus Linear Geometry Marcin Brynda, Laura Gagliardi, Per-Olof Widmark, Philip P. Power, Björn O. Roos Angewandte Chemie International Edition Published online May 3 2006Article （页面存档备份，存于互联网档案馆）
^ Large Differences in Secondary Metal−Arene Interactions in the Transition-Metal Dimers ArMMAr (Ar = Terphenyl; M = Cr, Fe, or Co): Implications for Cr−Cr Quintuple Bonding Giovanni La Macchia, Laura Gagliardi, Philip P. Power, and Marcin Brynda J. Am. Chem. Soc. 2008 ASAP Article doi:10.1021/ja0771890
^ The Many Ways To Have a Quintuple Bond Gabriel Merino, Kelling J. Donald, Jason S. D’Acchioli, and Roald Hoffmann J. Am. Chem. Soc. 2007 ASAP Article doi:10.1021/ja075454b
^ The Shortest Metal-Metal Bond Yet: Molecular and Electronic Structure of a Dinuclear Chromium Diazadiene Complex Kevin A. Kreisel, Glenn P. A. Yap, Olga Dmitrenko, Clark R. Landis, and Klaus H. Theopold Web Release Date: 30-Oct-2007; (Communication) doi:10.1021/ja076356t

[1] Quintuple Bond Makes Its Debut First stable molecule with fivefold metal-metal bonding is synthesized Steve Ritter Chemical & Engineering News September 26, 2005 Volume 83, Number 39 Article （页面存档备份，存于互联网档案馆）

[2] Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers Tailuan Nguyen, Andrew D. Sutton, Marcin Brynda, James C. Fettinger, Gary J. Long, and Philip P. Power Published online September 22 2005; 10.1126/science.1116789 Support info （页面存档备份，存于互联网档案馆）

[3] Quantum chemical calculations show that the uranium molecule U₂ has a quintuple bond Laura Gagliardi, Björn O. Roos Nature 433, 848-851 24 February 2005 Abstract （页面存档备份，存于互联网档案馆）

[4] New look for chemical bonds Belle Dumé 23 February 2005 PhysicsWeb Article （页面存档备份，存于互联网档案馆）

[5] Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans-Bent versus Linear Geometry Marcin Brynda, Laura Gagliardi, Per-Olof Widmark, Philip P. Power, Björn O. Roos Angewandte Chemie International Edition Published online May 3 2006Article （页面存档备份，存于互联网档案馆）

[6] Large Differences in Secondary Metal−Arene Interactions in the Transition-Metal Dimers ArMMAr (Ar = Terphenyl; M = Cr, Fe, or Co): Implications for Cr−Cr Quintuple Bonding Giovanni La Macchia, Laura Gagliardi, Philip P. Power, and Marcin Brynda J. Am. Chem. Soc. 2008 ASAP Article doi:10.1021/ja0771890

[7] The Many Ways To Have a Quintuple Bond Gabriel Merino, Kelling J. Donald, Jason S. D’Acchioli, and Roald Hoffmann J. Am. Chem. Soc. 2007 ASAP Article doi:10.1021/ja075454b

[8] The Shortest Metal-Metal Bond Yet: Molecular and Electronic Structure of a Dinuclear Chromium Diazadiene Complex Kevin A. Kreisel, Glenn P. A. Yap, Olga Dmitrenko, Clark R. Landis, and Klaus H. Theopold Web Release Date: 30-Oct-2007; (Communication) doi:10.1021/ja076356t

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