CCl3+ and CBr3+ salts with the [Al(ORF)4]− and [(FRO)3Al–F–Al(ORF)3]− anions (RF = C(CF3)3)

Abstract

The CX₃⁺ salts [CCl₃]⁺[Al(OR^F)₄]⁻1, [CCl₃]⁺[(R^FO)₃Al–F–Al(OR^F)₃]⁻2, [CBr₃]⁺[Al(OR^F)₄]⁻3, [CBr₃]⁺[(R^FO)₃Al–F–Al(OR^F)₃]⁻4 (R^F = C(CF₃)₃) were prepared in 56 to 85% yield from CX₄ (X = Cl, Br) and the corresponding silver salts (weight balance, NMR, IR, X-ray structure of 1). The most convenient solvent for the preparation of 1 and 2 is SO₂ClF but for 3 and 4 it is SO₂. The reactions are complete after about three days stirring at −30 to −40 °C. The salts are stable for weeks in solution at −40 °C and stable for a few hours at RT in the solid state. In SO₂ClF (1, 2) or SO₂ (3, 4) solution they decompose slowly at −20 °C and within several hours at RT; in general the CBr₃⁺ salts are more stable than the CCl₃⁺ homologues. The decomposition products were assigned as CCl₃F and primarily CBr₂F₂ (which likely forms as a Lewis acid induced disproportionation product of the initial CBr₃F). The C-X vibrations of the salts were found in the expected range and the assignments were made based on experimental and calculated data. The IR spectrum of a CBr₃⁺ salt is for the first time reported here.