Coordination Chemistry of Higher Oxidation States. Part 36. Periodato Complexes of Palladium(IV) and Platinum(IV). Crystal Structure of K₄Na₂[Pt(OH)₂(HIO₆)₂]·10H₂O

Abstract

Periodate complexes of Pd(IV) and Pt(IV) have been prepared from [MC1₆]^2- (M = Pd or Pt) and IO₄ ⁻ in aqueous alkaline solution. They are formulated as M'₆[M(OH)₂(HIO₆)₂].nH₂O (M' = Na or K) on the basis of analysis, vibrational spectroscopy, and an X-ray structure determination of the platinum complex. The title compound crystallizes in the triclinic space group PI with unit cell parameters a = 7.588(2), b = 8.110(2), c = 9.864(2) Å, a = 82.00(2), β = 83.79(2), γ = 81.76(2)° with Z = 1. Based on 2283 observed reflections (F > 3σ(F)), the structure refined to R = 0.034. Two bidentate [HIO₆]^4- anions coordinate to a central Pt atom which is also coordinated by two trans OH groups. The charge balance is maintained by sodium and potassium cations which are extensively hydrated. ¹⁹⁵Pt and ¹²⁷I NMR data are reported, and the variation in the former with pH interpreted in terms of differing degrees of protonation of the anions. EXAFS data are reported for the platinum complex in solution at pH = 2.

Key Words:

• Palladium
• platinum
• periodate complex
• X-ray structure