Oxycation

{{Short description|Positively charged polyatomic ion containing oxygen}} An '''oxycation''', or '''oxocation''', is an ion with the generic formula {{chem|A|''x''|O|''y''|''z''+}} (where A represents a chemical element and O represents an oxygen atom). Their names normally end with the suffix "-ium" or "-yl".{{refn|However, the International Union of Pure and Applied Chemistry standard book on nomenclature of inorganic chemistry does not mention "oxycation". {{Cite book |url=https://iupac.org/wp-content/uploads/2016/07/Red_Book_2005.pdf |title=Nomenclature of inorganic chemistry: IUPAC recommendations 2005 |date=2005 |publisher=Royal society of chemistry |isbn=978-0-85404-438-2 |editor-last=Union internationale de chimie pure et appliquée |location=Cambridge |access-date=2025-05-22}}}}

==Isolable oxycations== thumb|Structural details of the acetyl cation.<ref name=Kochi/> A few salts of oxycations have been reported. They are all associated with lighter main group elements. The nitrogen-containing cations are {{chem2|NO+}} and {{chem|NO|2|+}}. The latter is the active species in nitration reactions.

The Friedel-Crafts reaction is a classical organic reaction for attachment of acyl groups to arenes. The active acylating agent is often an acylium ion, several of which have been isolated..<ref name=Kochi>{{cite journal |doi=10.1039/B407654K |title=Structural effects of carbon monoxide coordination to carbon centers. σ and π Bindings in aliphatic acyl versus aromatic aroyl cations |date=2004 |last1=Davlieva |first1=Milya G. |last2=Lindeman |first2=Sergey V. |last3=Neretin |first3=Ivan S. |last4=Kochi |first4=Jay K. |journal=New Journal of Chemistry |volume=28 |issue=12 |page=1568 }}</ref><ref>{{cite journal |doi=10.1021/ja01026a025 |title=Crystal structure of a Friedel-Crafts intermediate. Methyloxocarbonium hexafluoroantimonate |date=1968 |last1=Boer |first1=F. Peter |journal=Journal of the American Chemical Society |volume=90 |issue=24 |pages=6706–6710 }}</ref>

==Oxycation nomenclature== ===Main group species=== * {{chem2|NO+}} - example: nitrosyl tetrafluoroborate * {{chem|NO|2|+}} - example: nitronium tetrafluoroborate * {{chem|ClO|2|+}} - example: chloryl hexafluororuthenate<ref>{{Cite journal | last6 = Vigner | first5 = M. | last5 = Nierlich | first6 = J. | journal = Inorganic Chemistry| pages = 102–109| issue = 1 | volume = 30 | first4 = L. | last4 = Meublat | last1 = Bougon| year = 1991 | title = Preparation characterization and crystal structure of chloryl hexafluororuthenate(1-). Crystal structure of {{chem|[ClF|2|]|+|[RuF|6|]|-}} | first1 = R. | last2 = Cicha | first3 = M. | last3 = Lance | first2 = W. V. | doi = 10.1021/ic00001a019}}</ref>

More complicated oxycations include species like SOF₃⁺.<ref>{{cite journal |last1=Brownstein |first1=M. |last2=Dean |first2=P. A. W. |last3=Gillespie |first3=R. J. |title=The Trifluorosulphur(VI) Oxide Cation, SOF₃⁺ |journal=Journal of the Chemical Society D: Chemical Communications |date=1970 |page=9 |doi=10.1039/C29700000009}}</ref> Aluminyl, antimonyl, bismuthyl derivatives more closely resemble the situation for transition metal oxy cations in the sense that they are bonded to many Lewis bases. The cation [Bi₆(O)₄(OH)₄]⁶⁺, a face-capped octahedral cluster, is one example.<ref>{{cite journal |last1=Sundvall |first1=Bengt |title=Crystal Structure of Tetraoxotetrahydroxohexabismuth (III) Perchlorate Heptahydrate, Bi₆O₄(HO)₄(ClO₄)6.7H₂O: An X-ray and Neutron Diffraction Study |journal=Inorganic Chemistry |date=1983 |volume=22 |issue=13 |pages=1906–1912 |doi=10.1021/ic00155a017}}</ref>

===Transition metal species=== Many transition compounds that contain an oxo ligand can be viewed as salts of a hypothetical "oxycation." In condensed phase, they are always complexed with strong Lewis bases. * {{chem2|TiO(2+)}} - example: titanyl sulfate, {{chem2|Ti(O)SO4(H2O)}}.<ref>{{cite journal|title=Structure of Anhydrous Titanyl Sulfate, Titanyl Sulfate Monohydrate and Prediction of a New Structure|last1=Gatehouse|first1=B. M.|last2=Platts|first2=S. N.|last3=Williams|first3=T. B.|journal=Acta Crystallographica Section B|year=1993|volume=49|issue=3|pages=428–435|doi=10.1107/S010876819201320X|bibcode=1993AcCrB..49..428G }}</ref> * {{chem2|VO(3+)}} - example: vanadyl chloride, VOCl₃ * {{chem2|VO(2+)}} - example: vanadyl phosphate, VO(HPO₄) * CrO₂²⁺ - example: chromyl chloride, CrO₂Cl₂<ref name=Sis>{{cite book|doi=10.1002/9780470132333.ch63|title=Inorganic Syntheses|pages=205–207|volume=2|year=1946|last1=Sisler|first1=Harry H.|chapter=Chromyl Chloride &#91;Chromium(VI) Dioxychloride&#93; |isbn=9780470132333}}</ref> * MoO³⁺ - molybdenyl chloride, MoOCl₃.<ref>{{cite journal |last1=Olah |first1=George |last2=Welch |first2=John |last3=Surya Prakash |first3=G. |last4=Ho |first4=Tse-Lok |title=Synthetic Methods and Reactions; XXIV¹. Oxidative Cleavage of Hydrazones with Molybdenyl Chloride (MoOCl₃) or Molybdenum Hexafluoride and Reductive Cleavage of Oximes with Molybdenyl Chloride/Zinc |journal=Synthesis |date=2002 |volume=1976 |issue=12 |pages=808–809 |doi=10.1055/s-1976-24211}}</ref> * FeO²⁺ - examples include many ferryl intermediates

===Actinide species=== * {{chem2|PaO(3+)}} * {{chem|UO|2|+}},<ref>{{cite book |title=Österreichische Chemiker-Zeitung |publisher=Springer |date=1965 |volume=66 |url=https://books.google.com/books?id=8bbnAAAAMAAJ&q=oxykationen | language=de |access-date=21 May 2025 |page=52}}</ref> {{chem|NpO|2|+}},<ref name="Np">{{Cite Q|Q60920989}}</ref> {{chem|PuO|2|+}}, {{chem|AmO|2|+}} * {{chem|UO|2|2+}}, {{chem|NpO|2|2+}},<ref name="Np" /> {{chem|PuO|2|2+}}, {{chem|AmO|2|2+}}

==Oxycations in the gas-phase== While species like vanadyl (VO²⁺ and VO³⁺) do not exist in solution, some oxycations can be generated in the vacuum chamber of mass spectrometers. Using ion cyclotron resonance, these oxy cations have been shown to react even with simple hydrocarbons, attesting to the high reactivity.<ref>{{cite journal |last1=Gunay |first1=Ahmet |last2=Theopold |first2=Klaus H. |title=C−H Bond Activations by Metal Oxo Compounds |journal=Chemical Reviews |date=2010 |volume=110 |issue=2 |pages=1060–1081 |doi=10.1021/cr900269x |pmid=20143877 }}</ref>

==See also== * Oxyanion * List of aqueous ions by element

==References== {{Reflist}}

Category:Cations Category:Oxycations