| 词条 | Four-center two-electron bond |
| 释义 |
A 4-center 2-electron (4c–2e) bond is a type of chemical bond in which four atoms share two electrons in bonding, with a net bond order of {{1/2}}. This type of bonding differs from the usual covalent bond, which involves two atoms sharing two electrons (2c–2e bonding). Four-center two-electron bonding is postulated in certain cluster compounds. For instance, the borane {{chem|B|6|H|7|-}} anion, is a {{chem|B|6|H|6|2-}} octahedron with an additional proton attached to one of the triangular faces.[1] As a result, the octahedron is distorted and a B–B–B–H rhomboid ring can be identified in which this 4c–2e bonding takes place. This type of bonding is associated with electron deficient rhomboid rings in general[2] and is a relatively new research field, fitting in with the already well established three-center two-electron bond. An example of a purely organic compound with four-center two-electron bonding is the adamantyl dication.[3] The bond joins the four bridgehead atoms in a tetrahedral geometry. Tetracyanoethylene forms a dianionic dimer in which the two alkenes are joined face-to-face by a rectangular four-center two-electron bond.[4] Various solid salts of this dianion have been studied to determine bond strengths and vibrational spectroscopic details.[5]{{clear left}}References1. ^{{cite journal |title= A new 4c–2e bond in {{chem|B|6|H|7|-}} |first1= K. |last1= Hofmann |first2= M. H. |last2= Prosenc |first3= B. R. |last3= Albert |journal= Chem. Commun. |date= 2007 |volume= 2007 |pages= 3097–3099 |doi= 10.1039/b704944g }} {{chemical bonds}}{{DEFAULTSORT:Four-Center Two-Electron Bond}}2. ^{{cite journal |title= Electron-Deficient Bonding in Rhomboid Rings |first1= M. M. |last1= Balakrishnarajan |first2= R. |last2= Hoffmann |authorlink2= Roald Hoffmann |journal= J. Am. Chem. Soc. |year= 2004 |volume= 126 |issue= 40 |pages= 13119–13131 |doi= 10.1021/ja0467420 }} 3. ^{{cite journal|first1=Matthias|last1=Bremer|first2=Paul von Ragué|last2=Schleyer|first3=Karl|last3=Schötz|first4=Michael|last4=Kausch|first5=Michael|last5=Schindler|title=Four-Center Two-Electron Bonding in a Tetrahedral Topology. Experimental Realization of Three-Dimensional Homoaromaticity in the 1,3-Dehydro-5,7-adamantanediyl Dication|journal=Angew. Chem. Int. Ed. Engl.|date=1987|volume=26|page=761–763|doi=10.1002/anie.198707611}} 4. ^{{cite journal |title= Exceptionally Long (≥2.9 Å) CC Bonding Interactions in {{chem|π-[TCNE]|2|2−}} Dimers: Two-Electron Four-Center Cation-Mediated CC Bonding Interactions Involving π* Electrons |last1= Del Sesto |first1= R. E. |last2= Miller |first2= J. S. |last3= Lafuente |first3= P. |last4= Novoa |first4= J. J. |journal= Chemistry |year= 2002 |volume= 8 |issue= 21 |pages= 4894–4908 |pmid= 12397591 |doi= 10.1002/1521-3765(20021104)8:21<4894::AID-CHEM4894>3.0.CO;2-2 }} 5. ^{{cite journal |last1= Casado|first1= J. |last2= Burrezo |first2= P. M. |last3= Ramírez |first3= F. J. |last4= Navarrete |first4= J. T. L. |last5= Lapidus |first5= S. H. |last6= Stephens |first6= P. W. |last7= Vo |first7= H.-L. |last8= Miller |first8= J. S. |last9= Mota |first9= F. |last10= Novoa |first10= J. J. |title= Evidence for Multicenter Bonding in Dianionic Tetracyanoethylene Dimers by Raman Spectroscopy |journal= Angew. Chem. Int. Ed. |doi= 10.1002/anie.201207813 |date=2013|volume=52|issue=25|page=6421–6425 }} 1 : Chemical bonding |
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