[Palladium-decabismuth(4+)]-tetrakis(tetrachloridoaluminate) Cluster Compound, [Pd@Bi10][AlCl4]4: Synthesis, Crystal Structure, and Electronic Structure

Black, needle-like single crystals of [Pd@Bi10][AlCl4]4 were synthesized in a one-pot reaction between PdCl2, Bi, and BiCl3 at 180 °C in the Lewis acidic ionic liquid (LAIL) medium [BMIm]Cl∙4.2AlCl4 (BMIm = 1-n-butyl-3-methylimidazolium). Single-crystal X-ray diffraction revealed that the compound crystallizes in the triclinic space group P1¯ with the unit cell parameters a = 11.0233(5) Å, b = 26.1892(14) Å, c = 26.2687(14) Å, α = 90.842(2)°, β = 92.1940(10)°, γ = 91.164(2)°, closely matching its platinum-containing analog. The structure features pentagonal antiprismatic [Pd@Bi10]4+ cluster cations charge-balanced by tetrahedral [AlCl4]− anions. Bonding and charge analysis reveal unoptimized Pd–Bi and strong Bi–Bi covalent interactions consistent with electronegativity trends and the previously reported host–guest model. Electronic structure calculations performed with the TB-LMTO-ASA program show that [Pd@Bi10][AlCl4]4 exhibits semiconducting behavior, suggesting a bandgap opening of 0.71 eV.