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Herein, the synthesis of ferrocene-containing salts is presented. Acylation of ferrocene (Fc) according to the Friedel-Crafts method led to ω-bromoacyl ferrocenes. The ω-bromoacyl ferrocenes were subsequently introduced to quaternization reaction with tri- tert -butyl phosphine, which resulted in phosphonium salts. Obtained phosphonium salts were characterized by physical methods. The electrochemical properties of phosphonium salts were studied by cyclic voltammetry (CV). It was found that the replacement of n -butyl fragments at the phosphorus atom by tert -butyl leads to a more anodic potential shift. In contrast to isolobal structures Fc-C(O)(CH 2 ) n P + ( n -Bu) 3 X - and Fc-(CH 2 ) n+1 P + ( n -Bu) 3 X - , the CV curves of Fc-C(O)(CH 2 ) n P + ( t -Bu) 3 X - and Fc-(CH 2 ) n+1 P + ( t -Bu) 3 X - did not show a large discrepancy between forward and reverse currents. The transformation of the C=O groups to CH 2 fragments had a significant effect on the electrochemical properties of ferrocene salts, the oxidation potential of which is close to that of pure ferrocene.

Analysis of infrared spectra of palladium nanoparticles (NPs) immersed in the tri-tert-butyl-R-phosphonium-based ionic liquids (ILs) demonstrates that both cations and anions of the ILs interact with the NPs. According to quantum-chemical simulations of these interactions, the binding energy of anions to the Pd6 cluster, taken as a minimal-size model of the NPs, increases from ∼6 to ∼27 kcal mol(-1) in the order [PF6](-)≈ [BF4](-) < [Tf2N](-) < [OTf](-) < [Br](-)≪ [TFA](-). In contrast, the binding energy for all types of the [Bu(t)3PR](+) cations slightly varies at about ∼22 kcal mol(-1) only moderately depending on the choice of the R moiety (n-pentyl, 2-hydroxyethyl, 2-methoxyethyl, 2-ethoxy-2-oxoethyl). As a result, the energies of interaction between a Pd6 cluster and various ion pairs, formed by the abovementioned counter-ions, follow the order found for the anions and vary from ∼24 to ∼47 kcal mol(-1). These values are smaller than the energy of addition of a Pd atom to a Pdn cluster (∼58 kcal mol(-1)), which suggests kinetic stabilization of the NPs in phosphonium-based ILs rather than thermodynamic stabilization. The results are qualitatively similar to the trends found earlier for interactions between palladium clusters and components of imidazolium-based ILs, in spite of much larger contributions of the London dispersion forces to the binding of the [Bu(t)3PR](+) cations to the cluster (up to 80%) relative to the case of 1-R-3-methylimidazolium cations (up to 40%).