Blocking {RhCl}²⁺ disorder in the crystal structure of a [SiW₁₁O₃₉{RhCl}]⁶⁻ salt: Direct localization of the heterometal in a monosubstituted Keggin anion

Heating [γ-SiW₁₀O₃₆]⁸⁻ with rhodium (II) acetate at 60 °C results in the formation of [SiW₁₁O₃₉{RhCl}]⁶⁻, isolated as K₈[SiW₁₁O₃₉{RhCl}][Rh₂(CH₃COO)₄Cl₂]·8H₂O (1). Unique feature of the crystal structure of 1 is fully ordered Keggin anion, allowing localization of the {RhCl}²⁺ fragment directly from X-ray diffraction data (Rh-Cl 2.212(5) Å Rh-O 1.96–2.13 Å). The product was also characterized by XRPD, IR and elemental analysis. According to coupled HPLC-ICP-AES technique the [SiW₁₁O₃₉{RhCl}]⁶⁻ anion selectively forms in the reaction.