title: Speciation in the AlCl3/SO2Cl2 catholyte system.
abstract: The fundamental chemical behavior of the AlCl(3)/SO(2)Cl(2) catholyte system was investigated using (27)Al NMR spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction. Three major Al-containing species were found to be present in this catholyte system, where the ratio of each was dependent upon aging time, concentration, and/or storage temperature. The first species was identified as [Cl(2)Al(mu-Cl)](2) in equilibrium with AlCl(3). The second species results from the decomposition of SO(2)Cl(2) which forms Cl(2)(g) and SO(2)(g). The SO(2)(g) is readily consumed in the presence of AlCl(3) to form the crystallographically characterized species [Cl(2)Al(mu-O(2)SCl)](2) (1). For 1, each Al is tetrahedrally (T(d)) bound by two terminal Cl and two mu-O ligands whereas, the S is three-coordinated by two mu-O ligands and one terminal Cl. The third molecular species also has T(d)-coordinated Al metal centers but with increased oxygen coordination. Over time it was noted that a precipitate formed from the catholyte solutions. Raman spectroscopic studies show that this gel or precipitate has a component that was consistent with thionyl chloride. We have proposed a polymerization scheme that accounts for the precipitate formation. Further NMR studies indicate that the precipitate is in equilibrium with the solution.
authors.affiliation: Sandia National Laboratories, Advanced Materials Laboratory, Albuquerque, New Mexico 87106, USA. tjboyle@Sandia.gov
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Boyle
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Andrews
authors.forename: Todd M
authors.initials: TM
authors.lastname: Alam
authors.forename: David R
authors.initials: DR
authors.lastname: Tallant
authors.forename: Mark A
authors.initials: MA
authors.lastname: Rodriguez
authors.forename: David
authors.initials: D
authors.lastname: Ingersoll