Cationic Bismuth Aminotroponiminates: Charge Controls Redox Properties.

The behavior of the redox-active aminotroponiminate (ATI) ligand in the coordination sphere of bismuth has been investigated in neutral and cationic compounds, [Bi(ATI)(3)] and [Bi(ATI)(2)L-n][A] (L=neutral ligand; n=0, 1; A=counteranion). Their coordination chemistry in solution and in the solid state has been analyzed through (variable-temperature) NMR spectroscopy, line-shape analysis, and single-crystal X-ray diffraction analyses, and their Lewis acidity has been evaluated by using the Gutmann-Beckett method (and modifications thereof). Cyclic voltammetry, in combination with DFT calculations, indicates that switching between ligand- and metal-centered redox events is possible by altering the charge of the compounds from 0 in neutral species to +1 in cationic compounds. This adds important facets to the rich redox chemistry of ATIs and to the redox chemistry of bismuth compounds, which is, so far, largely unexplored.