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A quintuple bond in chemistry is an unusual type of chemical bond, first reported in 2005 for a dichromium compound. Single bonds, double bonds, and triple bonds are commonplace in chemistry. Quadruple bonds are rarer but occur currently among the transition metals, especially for Cr, Mo, W, and Re, e.g. ()4− and ()2−. In a quintuple bond, ten electrons participate in bonding between the two metal centers, allocated as σ2π4δ4. In some cases of high-order bonds between metal atoms, the metal-metal bonding is facilitated by ligands that link the two metal centers and reduce the interatomic distance. By contrast, the chromium dimer with quintuple bonding is stabilized by bulky terphenyl (2,6-()phenyl) ligands. The species is stable up to 200 °C.〔(''Quintuple Bond Makes Its Debut First stable molecule with fivefold metal-metal bonding is synthesized'' ) Steve Ritter Chemical & Engineering News 26 September 2005 Volume 83, Number 39〕〔''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 22 September 2005; 10.1126/science.1116789 (Support info )〕 The chromium-chromium quintuple bond has been analyzed with multireference ab-initio and DFT methods,〔(''New look for chemical bonds'' ) Belle Dumé 23 February 2005 PhysicsWeb〕 Diuranium compounds are rare, but do exist; for example, the UCl anion. In 2007 the shortest ever metal to metal bond (180.28 pm) was reported to exist also in a compound containing a quintuple chromium-chromium bond with diazadiene bridging ligands.〔''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 October 2007; (Communication) 〕 Other metal-metal quintuple bond containing complexes that have been reported include quintuply bonded dichromium with ()(2,4,6-trimethylphenyl)amine bridging ligands〔''Metal-Metal Distances at the Limit: A Coordination Compound with an Ultrashort Chromium-Chromium Bond'' Awal Noor, Frank R. Wagner, and Rhett Kempe Angew. Chem. Int. Ed. Published online 13 August 2008 〕 and a dichromium complex with amidinate bridging ligands.〔''Remarkably Short Metal-Metal Bonds: A Lantern-Type Quintuply BondedDichromium(I) Complex'' Yi-Chou Tsai, Chia-Wei Hsu, Jen-Shiang K. Yu, Gene-Hsiang Lee, Yu Wang, and Ting-Shen Kuo Agnew. Chem. Int. Ed. Published online 6 August 28 〕 Synthesis of quintuple bonds is usually achieved through reduction of a dimetal species using potassium graphite. This adds valence electrons to the metal centers, giving them the needed number of electrons to participate in quintuple bonding. Below is a figure of a typical quintuple bond synthesis. ==Dimolybdenum quintuple bonds== In 2009 a dimolybdenum compound with a quintuple bond and two diamido bridging ligands was reported with a Mo-Mo bond length of 202 pm.〔''Journey from Mo-Mo Quadruple Bonds to Quintuple Bonds'' Yi-Chou Tsai, Hong-Zhang Chen, Chie-Chieh Chang, Jen-Shiang K. Yu, Gene-Hsiang Lee, Yu Wang, and Ting-Shen Kuo J. AM. CHEM. SOC. 2009, 131, 12534–12535 〕 The compound was synthesised starting from potassium octachlorodimolybdate (which already contains a Mo2 quadruple bond) and a lithium amidinate, followed by reduction with potassium graphite: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quintuple bond」の詳細全文を読む スポンサード リンク
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