Structure and Characterization of CI₃⁺[Al{OC(CF₃)₃}₄]⁻; Lewis Acidities of CX₃⁺and BX₃

Abstract

Where is the charge? The positive charge of the CI3+ ion in CI3+[Al{OC(CF3)3}4]− is located exclusively on the I atoms (see resonance structures B–D), and not on the formal carbenium center A. According to calculations and experimental findings, the Lewis acidity of the CX3+ homologues (X=F–I) versus fluoride is reversed in comparison to that of the isoelectronic boron halides BX3, and decreases from CF3+ to CI3+.