Neutron Diffraction of Homopolyatomic Bismuth Ions in Liquid Bi5(AlCl4)3 and ab Initio Study of the Structure and Bonding of the Isolated Bi53+ Ion
Time-of-flight neutron diffraction measurements were carried out at 350 °C and 450 ± 5 °C for molten Bi5(AlCl4)3. Contributions from AlCl4- were estimated using molten LiAlCl4 data and yielded radial distribution functions RDFrem(r) that allowed for the determination of the D3h-Bi53+ structure: d(Bia-Bie) = 3.2 Å and d(Bie-Bie) = 3.4 Å. The functions RDFrem(r) were simulated successfully by a model of intermediate range order similar to the environment in Bi5(AlCl4)3 crystals. The first sharp diffraction peak (FSDP) occurs at ca. 1.2 Å-1 and suggests a distance between Bi53+ and AlCl4- ions of about 5.5 Å in close agreement with values for the solid (5.6-6.2 Å). The free D3h-Bi53+ ion was studied with RHF, MP2, and QCISD(T) methods. Effective core potentials were used in conjunction with polarized split-valence LANL1DZ basis sets. At the QCISD(T)/LANL1DZ+PP level, distances of d(Bia-Bie) = 3.073 Å and d(Bie-Bie) = 3.331 Å were determined. The Bia-Bie distances consistently are shorter by about Δ(Bi-Bi) = 0.26 Å in the free ion, by ca. 0.3 Å in Bi5(AlCl4)3 crystals, and by ca. 0.25 Å in the liquid. Natural population analysis shows a larger charge on Bia (+0.74) than on Bie (+0.51). Natural electron configuration analyses show intact 6s-type Bi lone pairs. The lowest-lying cluster MOs are a1' (radial), e'' (mixed), a2'' (∥), and e'(⊥), and they are illustrated via contour plots of partial electron density functions. The molecular graph of Bi53+ shows compelling evidence for strong bonding along all edges.
K. Ichikawa et al., "Neutron Diffraction of Homopolyatomic Bismuth Ions in Liquid Bi5(AlCl4)3 and ab Initio Study of the Structure and Bonding of the Isolated Bi53+ Ion," Inorganic Chemistry, vol. 36, no. 23, pp. 5284-5290, American Chemical Society (ACS), Nov 1997.
The definitive version is available at https://doi.org/10.1021/ic970608h
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