Vicinal dinitridoruthenium-substituted polyoxometalates γ-[XW ₁₀O₃₈{RuN}₂]^6- (X = Si or Ge)

Reaction of the divacant polyoxometalate K₈[γXW ₁₀O₃₆] (X = Si, Ge) with two equivalents of the metal-nitrido precursor Cs₂[Ru^VINCl₅], at room temperature in water, produ-ces K₂(Me₂NH₂) ₂H₂[γ-XW₁₀O₃₈-(RuN) ₂], X = Si (DMA-la) or Ge (DMA-lb). The X-ray crystal struc-tures of both complexes show mono-meric complexes with highly unusual vicinal terminal metal-nitrido units. The Ru=N bond lengths are 1.594(10) and 1.612(11) Å in la and lb, respectively. EXAFS studies confirmed the key structural assignments from X-ray crystallography. The XANES spectrum of DMA-1a, diamagnetism, NMR (²⁹Si and ¹⁸³W) chemical shifts, voltammetric behavior, reductive titrations with [PW₁₂O ₄₀]^4-, and computational data are all consistent with d² Ru^VI centers in these complexes. The FT-IR and Raman spectra show the expected vi-brational modes of the {γ-XW₁₀} unit and the Ru=N stretch at 1080 cm^-1, re-spectively. Interestingly, reduction of DMA-la by 4 equivalents of [PW¹²O⁴⁰] ^4- produces NH₃ in nearly quantitative yield. Cyclic voltammetry versus pH and calculations provide the energetics for the possible two-electron reduction and two-proton addition pro-cesses in this reaction.