Synthesis and physical properties of tris(dialkylamino)cyclopropenium bistriflamide ionic liquidsElectronic supplementary information (ESI) available: Synthesis and characterisation details of starting materials and TDAC salts; tables of typical 1H- and 13C-NMR chemical shift ranges, density data (with fit parameters), molar volumes, viscosity, viscosity fit parameters, conductivity, conductivity fit parameters, water contents of water-saturated bistriflamide ILs, crystallographic data for 3a an

The synthesis and properties of 23 tris(dialkylamino)cyclopropenium (TDAC) cations with the bistriflamide anion, NTf 2 − , are described. D 3h - and C 3h -symmetric cations ([C 3 (NR 2 ) 3 ]NTf 2 (R = Me, Et, Pr, Bu, Pent, Hex, Dec) and [C 3 (NRMe) 3 ]NTf 2 (R = Et, Bu, St), respectively) were synthesised by reaction of C 3 Cl 5 H with the corresponding amine. Reaction of alkoxydiaminocyclopropenium salts ([C 3 (NMe 2 ) 2 (OMe)] + and [C 3 (NEt 2 ) 2 (OMe)] + ) with amines led to two series of C 2v -symmetric salts ([C 3 (NMe 2 ) 2 (NR 2 )]NTf 2 (R = Et, Pr, Bu, Hex) and [C 3 (NEt 2 ) 2 (NR 2 )]NTf 2 (R = Me, Bu, Hex), respectively) and two series of C s -symmetric salts ([C 3 (NMe 2 ) 2 (NRMe)]NTf 2 (R = Et, Pr, Bu, Hex) and [C 3 (NEt 2 ) 2 (NRMe)]NTf 2 (R = Bu, Hex), respectively). In addition to characterisation by NMR, mass spectrometry and microanalysis, the salts were characterised by DSC, TGA, density, viscosity, conductivity and miscibility/solubility studies. Along with molecular weight, symmetry plays a significant role in determining melting points and viscosity, whereas density was found to depend only on molecular weight. Methyl groups were found to significantly decrease thermal stability, while increasing the size of the other alkyl groups was found to increase stability; this increase in stability is contrary to observations with other classes of ionic liquids and indicates an associative decomposition mechanism. Walden plots indicated that these are "good ionic liquids" but that significant ion-pairing occurs when at least two alkyl chains of size C 6 or larger are present. Diffusion coefficients of [C 3 (NBu 2 ) 3 ]NTf 2 revealed a relatively small loss of conductivity due to ion correlations. The chemical stability of [C 3 (NEt 2 ) 3 ]NTf 2 to various reagents (acid, base, redox) was investigated at 25 °C and 60 °C. Cyclic voltammetry indicated a relatively small electrochemical window of 3.6 V (due to a relatively low oxidation potential of 1.2 V). The X-ray structures of [C 3 (NMe 2 ) 3 ]NTf 2 and [C 3 (NPr 2 ) 3 ]NTf 2 are reported. An investigation of symmetry ( D 3h , C 3h , C 2v and C s ) and alkyl chain length (6-60 alkyl carbon atoms) effects on the physical properties of peralkylated triaminocyclopropenium bistriflamide salts.