Cobaltocene

Structural formula
	Staggered conformation
General
Surname	Cobaltocene
other names	Di (cyclopentadienyl) cobalt; Bis (cyclopentadienyl) cobalt;
Molecular formula	C 10 H 10 Co
Brief description	dark purple to black solid
External identifiers / databases
EC number	215-061-0
ECHA InfoCard	100.013.692
PubChem	92884
Wikidata	Q197663
properties
Molar mass	189.12 g mol −1
Physical state	firmly
Melting point	176-180 ° C
solubility	almost insoluble in water; soluble in benzene and tetrahydrofuran ;
safety instructions
H and P phrases	H: 228-317-334-341-351
	P: 201-210-280-302 + 352-308 + 313
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cobaltocene ( di (cyclopentadienyl) cobalt or bis (cyclopentadienyl) cobalt ), with the semi-structural formula [Co (Cp) ₂ ] or also [Co (C ₅ H ₅ ) ₂ ], is a metallocene , i.e. an organometallic compound with aromatic ring systems . Cobaltocene is structurally related to the very stable ferrocene . It was first synthesized in 1953 by EO Fischer .

properties

Vacuum-sublimated cobaltocene under a nitrogen atmosphere

Cobaltocene forms black crystal needles with a melting point of 176–180 ° C. It is readily soluble in non-polar solvents such as hexane or toluene . Cobaltocene is very sensitive to air, as in air rapid oxidation to Cobaltoceniumhydroxid, which is the yellow-green or yellow Cobaltocenium- cation , the 18 electron complex [Co (Cp) ₂ ] ⁺ contains (Cp = cyclopentadienyl) occurs.

{\ displaystyle \ mathrm {2 \ [Co ^ {+ II} (Cp) _ {2}] + O_ {2} +2 \ H_ {2} O \ longrightarrow 2 \ [Co ^ {+ III} (Cp) _ {2}] ^ {+} + 2 \ OH ^ {-} + H_ {2} O_ {2}}}

Binding relationships

Cobaltocene consists formally of a cobalt (II) cation and two cyclopentadienyl - anions (C ₅ H ₅^- ) together. Overall, there is an uncharged complex . The bonding conditions are similar to those of ferrocene : the cyclopentadienyl anions, as aromatics, have a delocalized π-electron system. Each of these two ligands can provide 6 π electrons to the Co (II) cation. The cobalt (II) cation itself has 7 electrons in the valence shell , so it still receives 12 electrons from the ligands, so that it has 7 + 12 = 19 valence electrons in the complex. It has one more electron than would be favorable according to the 18-electron rule , so that this electron has to occupy an antibonding molecular orbital . This fact also explains the easy oxidizability of cobaltocene to the cation with 18 valence electrons. The Cp-Cp distance is 340 pm. It is thus somewhat longer than in ferrocene (332 pm), which can be explained by the occupation of an antibonding orbital with an electron.

presentation

Cobaltocene can be prepared by reacting anhydrous cobalt (II) chloride or hexamine cobalt (II) chloride with cyclopentadienyl sodium in tetrahydrofuran (THF). The reaction must be carried out under protective gas because the starting materials and the product of the reaction are sensitive to air. The product can then be isolated and purified by sublimation in vacuo.

{\ displaystyle \ mathrm {CoCl_ {2} +2 \ NaCp \ longrightarrow CoCp_ {2} +2 \ NaCl}}

{\ displaystyle \ mathrm {Co (NH_ {3}) _ {6} Cl_ {2} +2 \ NaCp \ longrightarrow CoCp_ {2} +2 \ NaCl + 6 \ NH_ {3}}}

Individual evidence

^ ^A ^b Norman N. Greenwood, Alan Earnshaw: Chemistry of the elements , 1st edition, Wiley-VCH, Weinheim 1988, ISBN 3-527-26169-9 , page 1463
↑ ^a ^b Wolfgang A. Herrmann, Georg Brauer: Synthetic Methods of Organometallic and Inorganic Chemistry - Volume 8: Transition Metals Part 2 , Thieme, Stuttgart 1997, ISBN 3-13-103091-7 , page 13
↑ Data sheet Cobaltocen at AlfaAesar, accessed on February 8, 2010 ( PDF )(JavaScript required) . .
↑ Data Cobaltocene from Acros, accessed on 24 February 2010 .
↑ ^a ^b Data sheet bis (cyclopentadienyl) cobalt (II) from Sigma-Aldrich , accessed on November 8, 2019 ( PDF ).
^ EO Fischer, R. Jira: Di-cyclopentadienyl-cobalt (II). In: Journal of Nature Research B . 8, 1953, pp. 327-328 ( online ).
^ Christoph Elschenbroich: Organometallchemie , 6th edition, Teubner, Leipzig 2008, ISBN 978-3-8351-0167-8 , page 469
↑ Peter L. Pauson "Bis (cyclopentadienyl) cobalt Hexafluorophosphate" e-EROS Encyclopedia of Reagents for Organic Synthesis e-EROS 2001, John Wiley & Sons, doi : 10.1002 / 047084289X.rb123
^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .

Web links

Commons : Cobaltocen - collection of images, videos and audio files

[Greenwood_+_Earnshaw-1] A ^b Norman N. Greenwood, Alan Earnshaw: Chemistry of the elements , 1st edition, Wiley-VCH, Weinheim 1988, ISBN 3-527-26169-9 , page 1463

[Hermann_+_Brauer-2] Wolfgang A. Herrmann, Georg Brauer: Synthetic Methods of Organometallic and Inorganic Chemistry - Volume 8: Transition Metals Part 2 , Thieme, Stuttgart 1997, ISBN 3-13-103091-7 , page 13

[alfa-3] Data sheet Cobaltocen at AlfaAesar, accessed on February 8, 2010 ( PDF )(JavaScript required) . .

[4] Data Cobaltocene from Acros, accessed on 24 February 2010 .

[Sigma-5] Data sheet bis (cyclopentadienyl) cobalt (II) from Sigma-Aldrich , accessed on November 8, 2019 ( PDF ).

[ZNaturf_1953_327-6] EO Fischer, R. Jira: Di-cyclopentadienyl-cobalt (II). In: Journal of Nature Research B . 8, 1953, pp. 327-328 ( online ).

[Elschenbroich-7] Christoph Elschenbroich: Organometallchemie , 6th edition, Teubner, Leipzig 2008, ISBN 978-3-8351-0167-8 , page 469

[8] Peter L. Pauson "Bis (cyclopentadienyl) cobalt Hexafluorophosphate" e-EROS Encyclopedia of Reagents for Organic Synthesis e-EROS 2001, John Wiley & Sons, doi : 10.1002 / 047084289X.rb123

[HoWi2007-9] AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .