Cyclooctatetraenide anion

In chemistry, the cyclooctatetraenide anion or cyclooctatetraenide, more precisely cyclooctatetraenediide, is an aromatic species with a formula of [C₈H₈]²⁻ and abbreviated as COT²⁻. It is the dianion of cyclooctatetraene. Salts of the cyclooctatetraenide anion can be stable, e.g., dipotassium cyclooctatetraenide or disodium cyclooctatetraenide. More complex coordination compounds are known as cyclooctatetraenide complexes, such as the actinocenes.

Cyclooctatetraenide anion

Names
Preferred IUPAC name Cyclooctatetraenediide
Identifiers
CAS Number	34510-09-3 Y
3D model (JSmol)	Interactive image
InChI InChI=1S/C8H8/c1-2-4-6-8-7-5-3-1/h1-8H/q-2 Key: GSYKYIXVPVFJRF-UHFFFAOYSA-N
SMILES c1=c[cH-]c=c[cH-]c=c1
Properties
Chemical formula	C8H82−
Molar mass	104.15 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The structure is a planar symmetric octagon stabilized by resonance, meaning each atom bears a charge of −⁠1/4⁠. The length of the bond between carbon atoms is 1.432 Å. There are 10 π electrons.^[1] The structure can serve as a ligand with various metals.

List of salts

name	formula	CAS	remarks	references
Samarium(II) cyclooctatetraenide	Sm(C8H8)			[2]
Dipotassium samarium(II) cyclooctatetraenide	K2Sm(C8H8)2			[2]
Neodymium cyclooctatetraenide	Nd(C8H8)2
Terbium cyclooctatetraenide	Tb(C8H8)2
Protactinocene	(Pa(C8H8)2)	51056-18-9
Thorocene	(Th(C8H8)2)	12702-09-9
Uranocene	U(C8H8)2	11079-26-8	green
Neptunocene	(Np(C8H8)2)	154974-81-9	dark brown
Plutonocene	(Pu(C8H8)2)	37281-23-5	red
Cerocene	Ce3+(C8H81.5-)2	37205-27-9		[3]

See also

• Tropylium ion
• Cyclopentadienyl anion