Such behavior would be expected for the complexes in which the alkyl chloride must intercalate itself between the cyclopentadienyl rings to facilitate complexation.
In the latter case, the alkyl chloride becomes a radical-anion and can subsequently dissociate from the CTC and produce the chloride ion and the alkyl radical.
The extinction coefficient of each CTC was determined by using Beer's Law, where the extinction coefficient can be calculated from the slope and plotting the absorbance versus the concentration of the desired ferrocene derivative in either dichloromethane or benzyl chloride as the solvent, assuming that the low concentration of the ferrocene derivative and the high concentration of the alkyl chloride will cause only the CTC to be present in solution.
Depending on the steric constraints of both the ferrocene derivative and the alkyl chloride and on the ferrocenyl substituent effects, the association rate constants can vary in magnitude of one hundredfold.
2~I, in their study, were mixed with hydrocarbons, ethers, HFCs or alkyl chlorides
to produce nonflammable blends, and at least one of the blends was actually tested in a small refrigerator.