This graphite-intercalation compound boasts increased reduction power in comparison to naked potassium due to both increased reagent surface area and electron delocalization along the graphene pi framework. The reduction potential of KC8 has been reported as -2.04 V (vs. SCE).[1]
Procedure: In the glovebox, small Schlenk flask equipped with a magnetic stir bar (ideally glass-coated) was charged with equimolar amounts of oven-dried graphite powder and freshly-cut potassium. The flask was subsequently closed and transferred to the Schlenk line where it was evacuated. With vigorous stirring, the contents of the flask were heated with a heat-gun for approximately 30 min. or until the potassium has completely homogenized with the graphite to form a golden-bronze powder. The flask was subsequently transferred to the glovebox where it was stored in a scitillation vial.
Notes:
- Glass-coated stir bars are preferentially used to prevent undesirable decomposition of the teflon coating in common, run-of-the-mill stir bars. However, I’ve used uncoated stir bars and found no appreciable issues. The stir bar will degrade though judging by the darkening of the outer teflon layer.
- KC8 is a highly pyrophoric compound and should be handled under strict exclusion of air and moisture.
- Older or improperly made samples tend to have a burgundy red color.
- I prefer using a heat gun instead of an open flame because I’ve had issues overheating the contents of the Schlenk flask in the past. Using a heat gun makes the procedure more reliable and safe.
[1] Hodge, S. A.; Tay, H. H.; Anthony, D. B.; Menzel, R.; Buckley, D. J.; Cullen, P. L.; Skipper, N. T.; Howard, C. A.; Shaffer, M. S. P. Faraday Discuss. 2014 , 172 , 1379–1382.