- Sextuple bond
A sextuple bond is a type of
covalent bond involving 12 bondingelectron s. The only known molecules with true sextuple bonds (order 6) are diatomic Mo2 and W2, in the gaseous phase at very low temperatures. Although diatomic Cr2 and U2 have formal structures with twelve-electron bonds, their effectivebond order s (derived fromquantum chemistry calculations) are less than 5 (quintuple bond ). There is strong evidence to believe that no two elements in the periodic table can form a bond with greater order than 6. [cite journal | last = Roos | first = Björn O. | coauthors = Antonio C. Borin, and Laura Gagliardi | year = 2007 | title = Reaching the Maximum Multiplicity of the Covalent Chemical Bond | journal =Angewandte Chemie International Edition | doi = 10.1002/anie.200603600 | volume = 46 | pages = 1469 ]Mo2 can be observed in the gas phase at low temperatures (7K) by a laser evaporation technique using molybdenum sheet with for instance
near infrared spectroscopy orUV spectroscopy . [cite journal | title = On the dimers of the VIB group: a new NIR electronic state of Mo2 | author = D. Kraus, M. Lorenz and V. E. Bondybey | journal =PhysChemComm | year = 2001 | volume = 4 | pages = 44–48 | doi = 10.1039/b104063b] Like dichromium, a singlet state is expected from dimolybdenum. [cite journal | title = The Many Ways To Have a Quintuple Bond | author = Gabriel Merino, Kelling J. Donald, Jason S. D’Acchioli, and Roald Hoffmann | journal =J. Am. Chem. Soc. | year = 2007 | volume = 129 | issue = 49 | pages = 15295–15302 | doi = 10.1021/ja075454b] Higher bond order is reflected in shorterbond length of 1.94 Å.References
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