Acidity Quantification and Structure Analysis of Amide-AlCl Liquid Coordination Complexes for C Alkylation Catalysis.

Liquid coordination complexes (LCCs), which are formed between metal halides and donor molecules, represent promising catalysts. Six amide-AlCl LCCs were successfully synthesized, followed by their characterization through NMR, Raman, and UV-visible spectroscopy. The acidity of these LCCs was quantified by performing computational modelling of fluoride ion affinities (FIA) and experimental Gutmann-Beckett measurements. Spectroscopic analysis indicated bidentate coordination between amide ligands and Al, which induced asymmetric splitting of AlCl into diverse ions such as [AlClL], [AlCl], [AlClL], and [AlClL]. The computed FIA was found to align well with the experimental acidity trends, thereby confirming the proposed structure of the LCC. In the alkylation tests, the LCC with a high acidity demonstrated an increase in the yields of C-C alkylates. These results provide an in-depth understanding of the tuneable structures of amide-AlCl LCCs. The acidity of LCCs can be controlled by tuning the ratio of the organic ligand to AlCl, which allows bidentate coordination to facilitate asymmetric splitting of AlCl. The LCCs demonstrate a high degree of potential as versatile and sustainable acid catalysts in alkylation reactions. These findings may advance the foundational knowledge of LCCs for the purpose of targeted acid catalyst design.