Volatilisation of substituted ferrocene compounds of different sizes from room temperature ionic liquids: a kinetic and mechanistic study?

New Journal of Chemistry Pub Date: 2012-01-09 DOI: 10.1039/C2NJ20704D

Abstract

The volatilisation of a range of ferrocene compounds from a range of room temperature ionic liquids (RTILs) into a flow of nitrogen gas was investigated. Namely, n-butylferrocene, 1,1′-dimethylferrocene and ferrocene were investigated in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpyrr][NTf2]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]). Cyclic voltammetric and chronoamperometric monitoring of the ferrocene compound concentration allowed quantification of the rate constants of volatilisation, k, activation energies of volatilisation, Ea, and entropies of activation, ΔS?. The rate of volatilisation was found to be ferrocene > 1,1′-dimethylferrocene > n-butylferrocene, and trends in the rate constant of the volatilisation process as a function of molecular size and ionic liquid surface tension were investigated. These indicate that the transition state for the volatilisation is when the solute is located in the liquid surface, and that the creation of a cavity of some sort in the liquid surface is necessary to allow volatilisation.

Graphical abstract: Volatilisation of substituted ferrocene compounds of different sizes from room temperature ionic liquids: a kinetic and mechanistic study
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