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Hydrides in liquid chloroaluminates
David F Wassell1, Keith E Johnson, Lynn M Mihichuk
1Department of Chemistry and Biochemistry, University of Regina, Regina, Saskatchewan, Canada S4S 0A2.
The Journal of Physical Chemistry. B
|November 13, 2007
Summary
Calcium hydride (CaH2) in ionic liquids reacts differently based on acidity, forming new species like AlCl3H- and allanes. This species can be detected and its reactions with protic species and electrochemistry studied.
Area of Science:
- Inorganic Chemistry
- Electrochemistry
- Spectroscopy
Background:
- Ionic liquids, specifically 1-ethyl-3-methyl-1H-imidazolium chloroaluminates, are versatile reaction media.
- Calcium hydride (CaH2) is a reactive hydride source with potential applications in various chemical transformations.
Purpose of the Study:
- To investigate the reactivity of CaH2 in different chloroaluminate ionic liquid systems.
- To characterize the species formed during the reaction of CaH2.
- To explore the detection and electrochemical behavior of the AlCl3H- species.
Main Methods:
- Infrared (IR) spectroscopy to identify reaction products.
- UV-vis spectroscopy to detect the AlCl3H- species via reaction with 2,3-dichloro-1,4-naphthoquinone.
- Electrochemical methods to study the oxidation and reduction of the AlCl3H- derived species.
Main Results:
- CaH2 reduces the cation in Lewis basic systems and is inert in neutral salts.
- In Lewis acidic systems, CaH2 forms AlCl3H- and subsequently allanes.
- AlCl3H- reacts with protic species to yield H2 and can be electrochemically oxidized and reduced.
Conclusions:
- The speciation of CaH2 in chloroaluminate ionic liquids is highly dependent on the Lewis acidity of the medium.
- The AlCl3H- intermediate is a key species, with defined spectroscopic and electrochemical properties.
- Understanding these reactions is crucial for developing new synthetic methodologies using ionic liquids and metal hydrides.
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