Two RhIII-substituted polyoxoniobates and their base-induced transformation: [H2RhNb9O28]6− and [Rh2(OH)4Nb10O30]8−

Abstract

Two new rhodium-substituted polyoxoniobates, [H₂RhNb₉O₂₈]⁶⁻ (RhNb₉) and [Rh₂(OH)₄Nb₁₀O₃₀]⁸⁻ (Rh₂Nb₁₀) are reported. The two distinct Rh^III-substituted niobate clusters behave differently when the pH is raised with TMAOH: the Rh₂Nb₁₀ is stable until pH ∼ 12.7, but RhNb₉ dissociates to form RhNb₅ and RhNb₁₀, similar to some of our other metal-substituted niobates, such as the MNb₉ ions (M = Cr or Mn), which transform to MNb₁₀ when the solution pH is raised.