Onium compounds
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Onium compounds are cations derived by the protonation of mononuclear parent hydrides of elements of the nitrogen group (Group 15), chalcogens (Group 16), or halogens (Group 17), and similar cations derived by the substitution of hydrogen atoms in the former by other groups, such as organic radicals, or halogens, for example tetramethylammonium, and further derivatives having polyvalent additions, such as iminium and nitrilium. (IUPAC definition [1]; other definitions vary.)
They are also known as onium ions. Compounds of these ions are known as onium salts. Onium ions have a charge of +1; double onium ions have a charge of +2, and so on.
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[edit] Simple onium cations
- Group 15 (nitrogen group) onium cations:
- ammonium, a.k.a. azanium, NH+
4 (protonated ammonia, a.k.a. azane) - phosphonium, PH+
4 (protonated phosphine) - arsonium, AsH+
4 (protonated arsine) - stibonium, SbH+
4 (protonated stibine) - bismuthonium, BiH+
4 (protonated bismuthine)
- ammonium, a.k.a. azanium, NH+
- Group 16 (chalcogen) onium cations:
- oxonium, better known as hydronium, H3O+ (protonated water) (Hydronium implies a solvated or hydrated proton.) (May be called hydroxonium for disambiguation.)
- sulfonium, H3S+ (protonated hydrogen sulfide)
- selenonium, H3Se+ (protonated hydrogen selenide)
- telluronium, H3Te+ (protonated hydrogen telluride)
- Group 17 (halogen) onium cations, halonium ions, H2X+ (protonated hydrogen halides)
- fluoronium, H2F+ (protonated hydrogen fluoride)
- chloronium, H2Cl+ (protonated hydrogen chloride)
- bromonium, H2Br+ (protonated hydrogen bromide)
- iodonium, H2I+ (protonated hydrogen iodide)
- Group 14 (carbon group) onium cations (these ions use similar naming schemes. they do not strictly meet the IUPAC definition above):
- methanium, CH+
5 (protonated methane) (Sometimes methonium, but it has multiple definitions.) (Should not be called carbonium[2].) (Abundant in outer space.) - further alkanium cations, CnH(2n+3)+
- ethanium, C2H+
7 (protonated ethane) - propanium, C3H+
9 (propane protonated on an unspecified carbon)- propylium, a.k.a. propan-1-ylium (propane protonated on an end carbon)
- propan-2-ylium (propane protonated on the middle carbon)
- ethanium, C2H+
- silanium (sometimes silonium), SiH+
5 (protonated silane) (Should not be called siliconium.[3]) - germonium, GeH+
5 (protonated germane) - stannonium, SnH+
3 (protonated SnH+
2; not protonated stannane SnH4) - plumbonium, PbH+
3 (protonated PbH+
2)
- methanium, CH+
- Group 13 (boron group) onium cations (these ions use a similar naming scheme. They do not strictly meet the IUPAC definition above):
- Hydrogen onium cation (this ion uses a similar naming scheme. It does not strictly meet the IUPAC definition above):
- hydrogenonium, better known as trihydrogen cation, H+
3 (protonated [molecular] or [diatomic] hydrogen). (Abundant in outer space).
- hydrogenonium, better known as trihydrogen cation, H+
- Group 18 (noble gases) onium cations (these ions use a similar naming scheme. They do not strictly meet the IUPAC definition above):
- helionium, better known as helium hydride ion, HeH+ (protonated helium). (Abundant in outer space).
[edit] Onium cations with monovalent substitutions
- primary ammonium cations, RH3N+ or RNH+
3 (protonated primary amines)- hydroxylammonium, NH3OH+ (protonated hydroxylamine)
- methylammonium, CH3NH+
3 (protonated methylamine) - ethylammonium, C2H5NH+
3 (protonated ethylamine) - hydrazinium, a.k.a. diazanium, NH2NH+
3 (protonated hydrazine, a.k.a. diazane)
- secondary ammonium cations, R2NH+
2 (protonated secondary amines)- dimethylammonium (sometimes dimethylaminium), (CH3)2NH+
2 (protonated dimethylamine) - diethylammonium (sometimes diethylaminium), (C2H5)2NH+
2 (protonated diethylamine) - ethylmethylammonium, C2H5CH3NH+
2 (protonated ethylmethylamine) - diethanolammonium (sometimes diethanolaminium), (C2H4OH)2NH+
2 (protonated diethanolamine)
- dimethylammonium (sometimes dimethylaminium), (CH3)2NH+
- tertiary ammonium cations, R3NH+ (protonated tertiary amines)
- trimethylammonium (CH3)3NH+ (protonated trimethylamine)
- triethylammonium (C2H5)3NH+ (protonated triethylamine)
- quaternary ammonium cations, R4N+ or NR+
4- tetramethylammonium, (CH3)4N+
- tetraethylammonium, (C2H5)4N+
- tetrapropylammonium, (C3H7)4N+
- tetrabutylammonium, (C4H9)4N+ or abbreviated Bu4N+
- trimethyl ammonium compounds, (CH3)3RN+
- didecyldimethylammonium, (C10H21)2(CH3)2N+
- pentamethylhydrazinium, N(CH3)2N(CH3)+
3
- quaternary phosphonium cations, R4P+ or NP+
4- tetraphenylphosphonium, (C6H5)4P+
- secondary sulfonium cations, R2SH+ (protonated sulfides)
- dimethylsulfonium, (CH3)2SH+ (protonated dimethyl sulfide)
- tertiary sulfonium cations, R3S+
- trimethylsulfonium, (CH3)3S+
- secondary fluoronium cations, R2F+
- dichlorofluoronium, Cl2F+
[edit] Onium cations with polyvalent substitutions
- secondary ammonium cations having one double-bonded substitution, R=NH2+
- quaternary ammonium cations having one double-bonded substitution and two single-bonded substitutions, R=NR2+
- quaternary ammonium cations having two double-bonded substitutions, R=N=R+
- nitronium, NO+
2 - bis(triphenylphosphine)iminium, ((C6H5)3P)2N+
- nitronium, NO+
- tertiary ammonium cations having one triple-bonded substitution, R≡NH+
- tertiary ammonium cations having two partially double-bonded substitutions, R=-NH+=-R
- pyridinium, C5H5NH+ (protonated pyridine)
- quaternary ammonium cations having one triple-bonded substitution and one single-bonded substitution, R≡NR+
- tertiary oxonium cations having one triple-bonded substitution, R≡O+
- nitrosonium, N≡O+
- tertiary sulfonium cations having one triple-bonded substitution, R≡S+
- thionitrosyl, N≡S+
[edit] Double-onium dications
- hydrazinium dication, +H3NNH3+ (doubly protonated hydrazine)
- diazenium dication, +H2N=NH2+ (doubly protonated diazene)
- diazonium dication, +HN≡NH+ (doubly protonated nitrogen)
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