On iodido bismuthates, bismuth complexes and polyiodides with bismuth in the system BiI3/18-crown-6/I2

Abstract

Abstract The iodido bismuthates [Bi(18-crown-6)I2][BiI4] (1) and [Bi(18-crown-6)I2][Bi3I10] (2), the neutral complex [Bi(C6H14O4)I3](18-crown-6) (3) as well as the polyiodides [Bi(18-crown-6)I2][I5](18-crown-6) (4), [Bi(18-crown-6)I2]2[I14] (5) and [Bi(18-crown-6)I2]2[I19] (6) were prepared by reaction of BiI3, 18-crown-6, and I2 at T = 60–120 °C. The compounds 1–5 were prepared in [n-Bu3MeN][N(Tf)2] as an ionic liquid ([n-Bu3MeN]: tributylmethylammonium, [N(Tf)2]: bis(trifluoromethylsulfonyl)imide), whereas 6 was obtained only by direct reaction of the starting materials. The title compounds exhibit two different constitutions of the [Bi(18-crown-6)I2]+ cation as well as a non-charged, molecular [Bi(C6H14O4)I3] unit with a triethylene glycol ligand generated in situ by cleavage of the crown ether. Infinite chain-like [ BiI 2 / 1 I 4 / 2 ] − ∞ 1 ${}_{\infty }{}^{1}\left[{{\text{BiI}}_{2/1}{\text{I}}_{4/2}\right]}^{-}$ and [ Bi 6 I 18 / 1 I 4 / 2 ∞ 1 ] − ${{}_{\infty }{}^{1}\left[{\text{Bi}}_{6}{\text{I}}_{18/1}{\text{I}}_{4/2}\right]}^{-}$ anions occur in 1 and 2, whereas various polyiodide anions (e.g. [I3]−, [I5]−, [I7]−, [I9]−) with partly complex interaction are observed in 4, 5, and 6. The title compounds were characterized by single-crystal X-ray diffraction analysis and infrared spectroscopy. In the case of 1 and 2, the optical band gap was determined to be E g = 1.91 and 1.62 eV, respectively. Especially, the ionic-liquid-based synthesis affords the different metastable compounds with variable composition and structure in a narrow temperature range.