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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 especially for Cr, Mo, W, and Re, e.g. [Mo2Cl8]4- and [Re2Cl8]2- .2 In a quintuple bond, 10 electrons participate in bonding between the two metal centers, allocated as as σ2π4δ4. In some cases metal-metal bonding is facilitated by ligands that link the two metal centers and reduce the intermolecular distance. In contrast, the chromium dimer with quintuple bonding is stabilized by bulky 2,6-[(2,6-diisopropyl)phenyl]phenyl ligands or simply terphenyl ligand. The species is stable up to 200 °C. The chromium-chromium quintuple bond has been analyzed with multireference ab-initio and DFT methods. A 2007 theoretical study identified two global minima for quintuple bonded RMMR compounds: a trans-bent molecular geometry and surprisingly another trans-bent geometry with the R substituent in a bridging position.
Additional recommended knowledge
Also in 2005, a quintuple bond was postulated to exist in the hypothetical uranium molecule U2 based on computational chemistry. Diuranium compounds are rare but do exist such as the U2Cl82- anion.
In 2007 the shortest ever metal to metal bond (1.8028 Å) was reported to exist also in a compound containing a quintuple chromium-chromium bond.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Quintuple_bond". A list of authors is available in Wikipedia.|