{{Short description|Type of chemical bond}} {{distinguish|Pi bond}} {{multiple image | footer = Suitably-aligned f atomic orbitals can overlap to form a φ molecular orbital (a φ bond) | width = 120 | image1 = Phi-bond-f-orbitals-2D.png | image2 = Phi-bond-boundary-surface-diagram-2D.png | caption = Suitably-aligned f atomic orbitals can overlap to form a φ molecular orbital (a φ bond) }} In chemistry, '''phi bonds''' ('''φ bonds''') are usually covalent chemical bonds, where six lobes of one involved atomic orbital overlap six lobes of the other involved atomic orbital. This overlap leads to the formation of a bonding molecular orbital with three nodal planes which contain the internuclear axis and go through both atoms.
The Greek letter φ in their name refers to f orbitals, since the orbital symmetry of the φ bond is the same as that of the usual (6-lobed) type of f orbital when seen down the bond axis.
There was one possible candidate reported in 2005 of a molecule with phi bonding: a U−U bond in the molecule diuranium (U<sub>2</sub>).<ref>{{cite journal|last1=Gagliardi|first1=Laura|last2=Roos|first2=Björn O.|title=Quantum chemical calculations show that the uranium molecule U<sub>2</sub> has a quintuple bond|journal=Nature|year=2005|volume=433|issue=7028|pages=848–851|doi=10.1038/nature03249|url=http://archive-ouverte.unige.ch/unige:3652|bibcode = 2005Natur.433..848G|pmid=15729337|s2cid=421380}}</ref> However, later studies that accounted for spin–orbit interactions found that the bonding was only of fourth order.<ref name = Manz2017>{{cite journal | doi = 10.1039/c7ra07400j | journal = RSC Adv. | title = Introducing DDEC6 atomic population analysis: part 3. Comprehensive method to compute bond orders | author1 = T. A. Manz | year = 2017 | volume = 7 | issue = 72 | pages = 45552–45581| bibcode = 2017RSCAd...745552M |doi-access = free}}</ref><ref>{{Cite web|url=https://chab.ethz.ch/en/news-and-events/d-chab-news/2018/10/u2-the-diuran-molecule-has-a-quadruple-bond.html|title=The diuranium molecule has a quadruple bond|website=chab.ethz.ch|date=28 October 2018 |language=en|access-date=2020-03-21}}</ref><ref name=":0">{{Cite journal|last1=Knecht|first1=Stefan|last2=Jensen|first2=Hans Jørgen Aa|last3=Saue|first3=Trond|date=January 2019|title=Relativistic quantum chemical calculations show that the uranium molecule U<sub>2</sub> has a quadruple bond|journal=Nature Chemistry|language=en|volume=11|issue=1|pages=40–44|doi=10.1038/s41557-018-0158-9|pmid=30374039|bibcode=2019NatCh..11...40K |s2cid=53112083|issn=1755-4349}}</ref> Experimental evidence for phi bonding between a thorium atom and cyclooctatetraene in thorocene has been supported by computational analysis, though this mixed-orbital bond has strong ionic character and is not a traditional phi bond.<ref>{{Cite journal |last1=Minasian |first1=Stefan G. |last2=Keith |first2=Jason M. |last3=Batista |first3=Enrique R. |last4=Boland |first4=Kevin S. |last5=Clark |first5=David L. |last6=Kozimor |first6=Stosh A. |last7=Martin |first7=Richard L. |last8=Shuh |first8=David K. |last9=Tyliszczak |first9=Tolek |date=2014 |title=New evidence for 5f covalency in actinocenes determined from carbon K-edge XAS and electronic structure theory |journal=Chem. Sci. |language=en |volume=5 |issue=1 |pages=351–359 |doi=10.1039/C3SC52030G |issn=2041-6520}}</ref>
== References == {{Reflist}} {{Chemical bonding theory}}
Category:Chemical bonding Category:Hypotheses in chemistry