Synthesis, Characterization, 81Br NMR and Electronic Spectra of [(C4H9)4N][CrO3Br] and [(C4H9)4N][FeCl3Br]

Abstract

Two new ionic complexes of transition metals with tetrabutylammonium cation were synthesized. One of them is tetrabutylammonium bromotrioxochromate(VI), (C₄H₉)₄N [CrO₃Br] (TBABC), that easily synthesized in a nearly quantitative yield using a direct reaction of Cr(VI) oxide and tetrabutylammonium bromide. Another is tetyrabutylammonium bromotrichloroferrate(III), [(C₄H₉)₄N][FeCl₃Br], (TBABF), that has been synthesized by reaction of tetrabutylammonium bromide with FeCl₃ salt. These compounds were characterized by IR, UV/Visible, ⁸¹Br NMR, ¹³C NMR and ¹H NMR techniques. The electronic and vibrational spectra of TBABC and TBABF have been measured and studied. In TBABC the intervening band has been identified with oxygen-to-chromium charge transfer. This band exhibits a partially resolved vibrational progression or vibronic coupling due to excitation of a symmetric stretching mode in the CrO₃ group.