五重鍵

五重鍵（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

五重鍵很罕見，直到2005年才從一個二鉻化合物中發現，僅能在含鉻、鉬、鎢的化合物中發現。例如： ${\ce {[Mo2Cl8]^4-}}$ 和 ${\ce {[W2Cl8]^2-}}$ 。

在一個五重鍵中，兩個金屬原子間共有10個電子參與了成鍵，分布為：σ²π⁴δ⁴。

在某些化合物中，由於配位基的促進作用，連接了兩個金屬中心並減少了原子間距離。

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」配位基，或簡單的三聯苯配位基均可以使一個擁有五重鍵的鉻二聚物穩定，而這些化合物在200℃才會分解。^[1]^[2]

2005年，根據計算化學，化學家假設出一個存在五重鍵的雙鈾化合物 ${\ce {U2}}$ ^[3]^[4]，儘管雙鈾化合物很罕見，但確實存在諸如 ${\ce {[U2Cl8]^2-}}$ 的離子。

化學家^[誰？]陸續用多參考從頭計算和密度泛函理論分析了鉻-鉻五重鍵。^[5]

^[何時？]研究闡明了三聯苯配位基在其中扮演的作用：

側面的芳基和鉻原子的相互作用十分微弱，僅能微量的弱化五重鍵。^[6]

在2007年，發表的一個理論研究確定五重鍵的RMMR化合物存在兩個全局最小能量值：

其中之一是一個trans-彎折構型；而另外一個很令人驚訝，儘管也是trans-彎折構型，但R基團卻在一個橋頭的位置。^[7]

在2007年，在一個含有五重鉻-鉻鍵的化合物中發現了有記載以來最短的金屬-金屬鍵(1.8028 Å)。^[8]

拓展連結

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

參考文獻

^ 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 （頁面存檔備份，存於網際網路檔案館）
^ 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 （頁面存檔備份，存於網際網路檔案館）
^ 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 （頁面存檔備份，存於網際網路檔案館）
^ New look for chemical bonds Belle Dumé 23 February 2005 PhysicsWeb Article （頁面存檔備份，存於網際網路檔案館）
^ 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 （頁面存檔備份，存於網際網路檔案館）
^ 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 （頁面存檔備份，存於網際網路檔案館）

[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 （頁面存檔備份，存於網際網路檔案館）

[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 （頁面存檔備份，存於網際網路檔案館）

[4] New look for chemical bonds Belle Dumé 23 February 2005 PhysicsWeb Article （頁面存檔備份，存於網際網路檔案館）

[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 （頁面存檔備份，存於網際網路檔案館）

[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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