Tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids as lubricants.

Six new tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids (ILs), [C3(NR2)3]BEHP (NR2 = NEt2, NBuMe, NPr2, NBu2, NHex2, NDec2; BEHP = bis(2-ethylhexyl)phosphate), were prepared and characterised as potential lubricants. Thermophysical and thermochemical properties of these ILs were investigated, namely: viscosity, density, conductivity, miscibility, thermal stability and phase transitions. Miscibility studies indicated that [C3(NEt2)3]BEHP would not be suitable due to its water solubility and hexane immiscibility. [C3(NDec2)3]BEHP was not investigated as a lubricant due to its low purity (the chloride salt of this cation is also hexane miscible). Of the other four, [C3(NHex2)3]BEHP was found to exhibit significantly less wear for pin-on-disk test conditions than the standard phosphonium [P6,6,6,14]BEHP IL. The amount of wear was found to generally decrease with increasing molecular weight.

Highly-fluorinated Triaminocyclopropenium Ionic Liquids.

A series of highly-fluorinated triaminocyclopropenium salts, with up to six fluorous groups, were prepared and their properties as ionic liquids investigated. Reaction of pentachlorocyclopropane or tetrachlorocyclopropene with bis(2,2,2-trifluoroethyl)amine, HN(CH2 CF3 )2 , occurs in the presence of a trialkylamine, NR3 , to give cations with two fluorinated amino groups, [C3 (N(CH2 CF3 )2 )2 (NR2 )]+ (R=Et, Pr, Bu, Hex), with traces of [C3 (N(CH2 CF3 )2 )3 ]+ . Use of appropriate reagent ratios and reaction times and subsequent addition of a dialkylamine, HNR'R", gives cations with one fluorinated amino group, [C3 (N(CH2 CF3 )2 )(NR2 )(NR'R")]+ ((NR2 )(NR'R")=(NBu2 )2 , (NEt2 )(NPr2 ), (NBu2 )(NBuMe)). These cations were isolated as chloride salts and some of these were converted to bistriflamide, dicyanamide and triflate salts to provide ionic liquids. These salts were characterised by thermal (DSC and TGA) measurements and miscibility/solubility properties (determined in a range of solvents). Ionic liquids (ILs) were also characterised by density, viscosity and conductivity measurements where possible. X-ray diffraction studies of chloride salts showed the formation of fluorous regions and more hydrophilic ionic regions in the solid state.

Discrete Oligomers and Polymers of Chloride Monohydrate Can Form in Encapsulated Environments: Structures and Infrared Spectra of [Cl4 (H2 O)4 ]4- and {[Cl(H2 O)]- }∞.

A discrete tetrachloride tetrahydrate cluster, [Cl4 (H2 O)4 ]4- , was obtained with a partially-fluorinated triaminocyclopropenium cation, [C3 (N(CH2 CF3 )2 )(NEt2 )(NPr2 )]+ . The cluster consists of a [Cl2 (H2 O)2 ]2- square with each Cl- coordinated by another H2 O bridged to another Cl- . A 1D polymer of chloride monohydrate, {[Cl(H2 O)]- }∞ , was obtained with [C3 (N(CH2 CF3 )2 )2 (NBuMe)]+ . The tetrameric and polymeric structures were found to be computationally-unstable in the gas phase which indicates that an encapsulated environment is essential for their isolation. DFT and DFTB calculations were carried out on gas-phase [Cl4 (H2 O)4 ]4- to assist the infrared assignments. Anharmonically-corrected B3LYP transition frequencies were in close agreement with experiment, but DFTB models were only appropriate for qualitative interpretation. Solid-state DFTB calculations allowed the vibrational modes to be assigned. The results found are consistent with "discrete" chloride hydrates.

A Series of Discrete Dichloride Dihydrates: Characterisation and Symmetry Effects.

A series of three discrete dichloride dihydrates [Cl2 (H2 O)2 ]2- have been isolated with different triaminocyclopropenium (TAC) cations and with different crystallographic symmetries. The cluster exhibits D2h symmetry with the tris(dimethylamino)cyclopropenium cation [C3 (NMe2 )3 ]+ , C2h symmetry with the fluorinated cation [C3 (N(CH2 CF3 )2 )(NBu2 )2 ]+ (containing two 2,2,2-trifluoroethyl substituents) and C2v symmetry with the more fluorinated [C3 (N(CH2 CF3 )2 )2 (NBu2 )]+ cation. The effect of symmetry on the infrared spectra of the dichloride ion-pair clusters, as well as deuterated analogues, has been investigated. The D2h - and C2h -symmetric clusters each exhibit two stretching bands in the infrared at 3427 and 3368 cm-1 for D2h symmetry and 3444 and 3392 cm-1 for C2h symmetry, whereas the C2v -symmetric cluster exhibits three bands at 3475, 3426 and 3373 cm-1 . Computational studies were carried out on a [Cl2 (H2 O)2 ]2- cluster with C2v symmetry to aid the infrared band assignments.

One water to bind a chloride-chloride ion pair: isolation of discrete [Cl2(H2O)]2- in the solid state.

A discrete dichloride ion pair in the form of a monohydrate, [Cl2(H2O)]2-, was isolated using the triaminocyclopropenium cation [C3(NHex2)(N(CH2CF3)2)2]+. Although this ion pair is calculated to be unstable in the gas phase, the ionic lattice and weak CH-Cl hydrogen bonds assist the stabilization of the cluster. The D2O and HDO isotopomers were also prepared and characterized.