Purification of aluminum tridecamer salt using organic solvent precipitation

Aluminum tridecamer (Al₁₃) salt of 70% purity can be yielded by slowly adding base to a mixed aluminum chloride solution with sodium chloride as the primary byproduct. The purity of the so-produced Al₁₃ solution is typically increased to >90% using sulfate precipitation and nitrate metathesis reactions (the SO₄^2-/Ba²⁺ separation method). However, the presence of excess sulfate and, as demonstrated in this study, excess chloride ions can destabilize Al₁₃ clusters. This study applied the organic solvent precipitation technique to purify crude Al ₁₃ salt. The solution and solid-state ²⁷Al nuclear magnetic resonance (NMR) spectra indicate that Al₁₃ purity was >95%. The infrared adsorption spectra had clear Al₁₃ characteristic bands. The electrospray ionization mass spectrometry (ESI-MS) tests identified Al₁₃⁷⁺ species. The organic solvent precipitation method purified Al₁₃ clusters with minimal free Cl ^- ions. © 2010 Elsevier B.V. All rights reserved.