Pyridine Complexes of Iodobismuthate(III) Anions

We report a rare family of pyridine-coordinated iodobismuthate(III) salts supported by alkyltriphenylphosphonium and tetraphenylphosphonium cations. Reactions of BiI3 with Ph3PR+I− (R = Me, Et, nPr, nBu, Ph) in neat pyridine, followed by crystallization, yield structurally tunable bismuth-halide-pyridine anions dictated by reagent stoichiometry. Combination of BiI3 and Ph3PR+I− in 2:1 ratio produced [Ph3PR]2[BiI5Py], 1 (R = Me, Et, nPr, Ph), while combination in 1:1 ratio resulted in three compounds: [Ph3PR][cis-BiI4Py2], 2 (R = nPr, Ph), [Ph3PR][trans-BiI4Py2], 3 (R = Me, Et, Ph), and [Ph3PR]2[transoid-Bi2I8Py2], 4 (R = Me, Et, nPr, nBu, Ph). In many cases, the compounds were isolated as Py or Et2O solvates, and in some cases, multiple degrees of solvation or polymorphism were encountered. Hirshfeld analysis of 1–4 showed the major anion–cation/anion/solvent interactions to be H⋯I, H⋯H, and C⋯H. Diffuse reflectance measurements of representative compounds, all of which were yellow-orange to red-orange, revealed bandgaps in the range of 1.9–2.2 eV, where density-of-states KS-DFT calculations attribute the absorption to metal-centered charge transfer within the anionic unit. NLMO and QTAIM analyses further indicate predominantly ionic Bi(III)–I/pyridine bonding with robust inner-sphere coordination that is insensitive to anion speciation.