Fast atom bombardment mass spectrometry of low temperature chloroaluminate and chlorogallate melts

Abstract

Fast atom bombardment (FAB) mass spectrometric analyses of r m temperature cMoroalunlnate and cMorogallate mdten salts are described. Melts composed of AICI, or GaCi, with 1-butyipyridinium chloride (BPC) or l-methyi-3-ethyiimidazdlum chloride (MEIC) were investigated to determine the nature of the Ai or Ga species as a function of Lewis acidity. Acidic melts contain a molar excess of AICI, or GaCi,, whereas basic systems have a molar excess of the organlc chloride. Mass spectra of negative ions were selected by wing a Kratos MSBORFA, double focusing, forward geometry mass spectrometer. Ankns such as AIC14-, Ai2Ci,-, AiSCi8-, QaC14-, and Ga2Ci,-were detected along with subvalent monomer, dimer, and mlxed-valent species. I n addC tion, various oxychloro and hydroxychioro species of Ai and Ga have been klentifled as well as (catkrt-dlanlon) aggregate ions. Results obtained reflect the surface condensed phase chemistry and gas phase reaction pathways established by the energy imparted by the FAB ionization process.The technique of fast atom bombardment mass spectrometry (FAB-MS) was pioneered by Barber and co-workers ( I ) .They developed an ion source that accommodated nonvolatile materials (high molecular weight compounds of biological and biomedical importance), utilized the phenomenon of ion sputtering, and employed a beam of fast neutral atoms. This bombardment by 5-10 keV energy particles does not require thermal sample volatilization and thus avoids direct thermal decomposition. In addition, the method works for either positive or negative ions while providing structurally significant fragmentation. Bojeson (2) demonstrated that the application of this technique to inorganic salts dissolved in glycerol (for example) was a natural extension. By his investigation of coordination compounds, Bojeson showed that FAB-MS was a useful analytical tool for the study of strongly bound metal-organic ligand complexes. Recently, Ackerman et al. (3) have reported FAB-MS analyses (positive ion mode) of A1C13/ 1-butylpyridinium chloride (BPC) melts. Although characteristic changes in the pceitive ion mass spectra reflected changes in melt composition (Lewis acidity), an overall assessment of the anions present was not possible for their instrument. Conversely, Franzen et al. (4) have used secondary ion mass spectrometry (SIMS) with a 5-keV cesium primary ion beam to identify the major anionic species (AlCl;, A12C17-, and C1-) in chloroaluminate melts. Since the room temperature 1-butylpyridinium chloride or 1-methyl-3-ethylimidazolium (MEIC) chloroaluminate and chlorogallate melts PreseTable I. FAB Spectra of Acidic Chloroaluminate Melts m/za 2:l AlC13/BPCb 1.5:l AlC13/MEICb 149 169 247 283 301 325 361 381 399 459 2.3 15.0 16.4 17.6 1.2 6.6 6.5 3.5 6.5 3.9 1.3 36.3 11.2 15.1 1.0 3.4 0.6 0.9 2.6"Highest ion intensity in cluster. bAbsolute percent total intensity, i.e., the sum of ion currents of an isotopic cluster as percent of total ion current.are not fully characterized from the standpoint of higher anionic species such as...

Detection and Identification of Cations and Anions of Ionic Liquids by Means of Electrospray Ionization Mass Spectrometry and Tandem Mass Spectrometry

“…6 Other investigations of such anions by FAB have been reported. [7][8][9] These ionic liquids contained 1-ethyl-3-methylimidazolium (EMI) as the cation. [6][7][8][9] Later, clusters of substituted imidazolium salts were observed by FAB.…”

Preparation of novel, moisture-stable, Lewis-acidic ionic liquids containing quaternary ammonium salts with functional side chains

“…To investigate the parameters necessary for a salt to be liquid at or near room temperature we have heated a range of ammonium salts with zinc chloride in a 1+2 molar ratio and the results are shown in 13 The ionic liquid has a conductivity of 36 mS cm 21 at 40 °C and this increases exponentially with temperature, due to a decrease in the viscosity and hence an increase in the mobility of the ions in the melt. † The conductivity is similar to that found in alkylpyridinium-based ionic liquids 14 and is sufficient for them to be suitable media for electrochemical applications such † Electronic supplementary information (ESI) available: plot of conductivity vs. temperature for the ionic liquid formed from zinc chloride and choline chloride (2+1).…”

Oligomerisation of linear 1-olefins using a chlorogallate(III) ionic liquid

“…Lewis acidity of chlorogallate(III) systems was demonstrated to be the same, or even higher (χ GaCl3 > 0.67), than that of the analogous relevant chloroaluminates(III) [8]. At the same time, chlorogallate(III) ionic liquids appear to be much more resistant to hydrolysis than the chloroaluminate(III) ones [25].…”