Discrete Organofluoroaluminate Anions: Synthetic, Structural, and Spectroscopic Aspects

The reaction of alkylaluminum compounds (AlR3, R = Me, n-Bu) with the series of imidazolium-based fluorinating reagents [IPrH][F], [IPrH][(HF)F] and [IPrH][(HF)(2)F] led to the isolation of salts containing discrete triorganofluoroaluminate ([R3AlF](-)), diorganodifluoroaluminate ([R2AlF2](-)), and organotrifluoroaluminate ([RAlF3](-)) anions, respectively. The formation of [R2AlF2](-) and [RAlF3](-) anions was accompanied by the release of RH. The syntheses are effective, selective, and straightforward. The related reactions of an arylaluminum compound (AlPh3) resulted in a mixture of different phenylfluoroaluminate anions. All of the obtained products were characterized by NMR and Raman spectroscopy. Structural features of [IPrH][Me2AlF2] (2), [IPrH][MeAlF3] (3), [IPr][AlF4] (4), [IPrH][n-Bu3AlF] (5), [IPrH][n-Bu2AlF2] (6), [IPrH][n-BuAlF3] (7), [IPrH][Ph3AlF] (8), and [IPrH][PhAlF3] (10) were determined by single-crystal X-ray diffraction and compared with DFT calculations of structurally optimized salts.

Automated summary

The reaction of alkylaluminum compounds with imidazolium-based fluorinating reagents resulted in the isolation of salts containing different fluoroaluminate anions. The products were characterized by NMR, Raman spectroscopy, and single-crystal X-ray diffraction, with their structures compared with DFT calculations.