This work was developed in the course of a cooperation project with the Merck KGaA Company (Darmstadt) on weakly coordinating anions and their applications. The main target was the preparation of the new strong N-H acids bis[bis(perfluoroalkyl)- phosphinyl]imides (HFPI), bis(pentafluoroethyl)phosphinyl–(trifluoromethyl)sulfonylimide (HPSI), their salts and ionic liquids as well as the study of their catalytic properties. Most of the compounds were analysed by NMR, IR and Raman spectroscopy, mass spectrometry and elemental analysis and in some cases by single crystal X-ray diffraction. The new ionic liquids were characterized by measuring their viscosity, density, melting point, thermal properties, electrochemical stability, conductivity, water and ionic impurities.
The first chapter describes improved syntheses of the precursors of HFPI. By selective hydrolysing (CnF2n+1)3PF2 (n = 2, 4) pure bis(perfluoroalkyl)phosphinic, (CnF2n+1)2P(O)OH, and perfluoroalkylphosphonic, CnF2n+1P(O)(OH)2, acids have been obtained. PhPCl4 was found to be a suitable reagent to convert the acids into acid chlorides.
In chapter 2 formation of (C2F5)2P(O)NH2 by treatment of (C2F5)3PO with NH3 at low temperature is described. Both precursors (C2F5)2P(O)Cl and (C2F5)2P(O)NH2 were reacted in the presence of Et3N to form the salt [Et3NH][{(C2F5)2P(O)}2N]. The free acid was obtained by heating the salt in 100 % H2SO4 in vacuum. Its acidity was determined by different methods.
In chapter 3 the preparation of new MFPI salts (M = Li, Na, K, Cs, Ag, Mg, Zn, La, Eu, Ce, and Yb) is described. LiFPI can be used as an electrolyte for lithium ion batteries. One important application of lanthanide salts are their use as Lewis acid catalysts.
HFPI and the Na and K salts are suitable starting materials for the synthesis of new hydrophobic ionic liquids with the FPI anion as described in chapter 4. Relationships between their physico-chemical properties and their structures are discussed. FPI ionic liquids possess advanced properties such as: (i) melting points below 50 °C; (ii) hydrolytic stability in neutral aqueous solution up to 100 °C; (iii) thermal stability up to 280 °C; (iv) low viscosity; (v) high electrochemical stability; and (vi) they can be synthesized from industrially available materials.
In the fifth chapter another strong N–H acid (HPSI) and new ionic liquids with the PSI anion are presented. The properties of a series of ionic liquids with asymmetrical perfluoroanions, such as PSI anion, are reported here. The asymmetric species have significant lower melting points than the corresponding symmetric ionic liquids. Further properties of these PSI derivatives were also investigated and compared with related FPI and TFSI derivatives. Furthermore, [Et3NH][PSI] was characterized by X-ray crystallography.
The catalytic activity of the HFPI acid and some of its salts were investigated for acylation reactions of various compounds (with –OH, –NH, –SH functional groups) and the results are shown in chapter 6.
Finally, the last chapter presents the synthesis and characterization of new bis(pentafluoroethyl)phosphinic acid amides and hydrazides.