KC ₈

Crystal structure
__ K __ C
Crystal system	orthorhombic
Space group	Fddd (No. 70)
Lattice parameters	a = 492 pm c = 535 pm
General
Surname	KC8
other names	brown potassium graphite Level 1 potassium graphite
Ratio formula	KC 8
Brief description	bronze colored solid
External identifiers / databases
CAS number 12081-88-8 Wikidata Q84165389
properties
Molar mass	135.18 g mol −1
Physical state	firmly
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 260-314-318 P: 231 + 232-303 + 361 + 353-305 + 351 + 338-403 + 233-422-501
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

KC ₈ is a bronze-colored solid that is primarily used as a reducing agent . It belongs to the class of intercalation compounds .

presentation

KC _{8 was} first presented by Karl Fredenhagen and Gustav Cadenbach in 1926. Nowadays, the synthesis is carried out by mixing stoichiometric amounts of potassium and graphite . Heating this mixture causes the potassium to melt and the exothermic reaction to start immediately . The product forms within a short time in the form of a bronze-colored solid.

${\displaystyle {\ce {K + 8 C ->[{170 °C}] KC8}}}$

properties

KC ₈ in a Schlenk flask under an argon atmosphere .

KC ₈ is a highly reactive compound that sprays sparks when it comes into contact with air and must therefore be handled in a nitrogen or noble gas atmosphere.

In addition, this potassium graphite has a layer structure in which the carbon layers are separated by 5.35 Å. This is significantly larger than the distance between the carbon layers in graphite (3.35 Å) and is due to the placement of the potassium atoms between the layers. The carbon atoms of the carbon layers lie on top of one another, the potassium ions lie between the graphite layers. This results in the layer sequence C, K; C, K; ... . The potassium atoms, in turn, lie above and below the centers of the hexagons that the carbon forms.

The connection also has metallic conductivity. In the direction of the layers this is about 30 times and perpendicular to it about 10 times higher than in the corresponding directions in graphite.

use

KC ₈ is primarily used as a strong reducing agent. So used Mitsou Kira and his staff connect to the synthesis of stannylenes .

In an analogous way, Simon Aldridge et al. Use KC ₈ 2018 to reduce an aluminum iodide to the first nucleophilic aluminum anion.

KC ₈ can also serve as a catalyst for ethylene polymerization .

In addition, like many other intercalation compounds , KC _{8 is being} investigated in battery research.

See also

Commons : Potassium Graphite  - Collection of pictures, videos, and audio files

• Graphite intercalation compounds

Individual evidence

1. ↑ DP Divincenzo, NAW Holzwarth, S. Rabii: The electronic structure of KC8 . In: Physica B + C . tape 99 , no. 1-4 , January 1980, pp. 406-410 , doi : 10.1016 / 0378-4363 (80) 90268-5 .
2. ↑ MC Böhm, J. Schulte, R. Schlögl: Solid state electronic structure of potassium graphite intercalation compounds; the systems KC24 and KC8 . In: physica status solidi (b) . tape 196 , no. 1 , July 1, 1996, p. 131-144 , doi : 10.1002 / pssb.2221960114 .
3. ↑ ^{a b c d} H. Podall, WE Foster, AP Giraitis: Catalytic Graphite Inclusion Compounds. I. Potassium Graphite as a Polymerization Catalyst . In: The Journal of Organic Chemistry . tape 23 , no. 1 , January 1958, p. 82-85 , doi : 10.1021 / jo01095a025 .
4. ↑ ^{a b} Safety data sheet from KC ₈ . at Strem , accessed on January 29, 2020 . 
5. ^ Karl Fredenhagen , Gustav Cadenbach: The binding of potassium by carbon . In: Journal of Inorganic and General Chemistry . tape 158 , no. 1 , November 23, 1926, p. 249-263 , doi : 10.1002 / zaac.19261580122 .
6. ↑ DM Ottmers, HF Rase: Potassium graphites prepared by mixed-reaction technique . In: Carbon . tape 4 , no. 1 , May 1966, ISSN  0008-6223 , pp. 125-127 , doi : 10.1016 / 0008-6223 (66) 90017-0 .
7. ^ ^{A b} Wiberg, Egon , Wiberg, Nils : Holleman-Wiberg Textbook of Inorganic Chemistry . 102nd, heavily reworked and verb. Ed. De Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
8. ↑ ^{a b} Mitsuo Kira, Shintaro Ishida, Takeaki Iwamoto, Rika Yauchibara, Hideki Sakurai: New synthesis of a stable dialkylstannylene and its reversible complexation with tetrahydrofuran . In: Journal of Organometallic Chemistry . tape 636 , no. 1-2 , November 2001, pp. 144-147 , doi : 10.1016 / S0022-328X (01) 00998-6 .
9. ↑ Jamie Hicks, Petra Vasko, Jose M. Goicoechea, Simon Aldridge: Synthesis, structure and reaction chemistry of a nucleophilic aluminyl anion . In: Nature . tape 557 , no. 7703 , May 2018, p. 92-95 , doi : 10.1038 / s41586-018-0037-y .
10. ↑ Jiantie Xu, Yuhai Dou, Zengxi Wei, Jianmin Ma, Yonghong Deng: Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al) -Ion Batteries . In: Advanced Science . tape 4 , no. 10 , October 2017, p. 1700146 , doi : 10.1002 / advs.201700146 , PMID 29051856 , PMC 5644242 (free full text).
11. ↑ R. Tossici: Electrochemistry of KC [sub 8] in Lithium-Containing Electrolytes and Its Use in Lithium Ion Cells . In: Journal of The Electrochemical Society . tape 144 , no. 1 , 1997, p. 186 , doi : 10.1149 / 1.1837383 .