Notes. High-valent ruthenium oxo complexes of NNN′N′-tetramethyl-3,6-dimethyl-3,6-diazaoctane-1,8-diamine (L¹). X-ray crystal structure determination of cis-[Ru^III(L¹)Cl₂]ClO₄

The reaction of K₂[RuCl₅(H₂O)] with NNN′N′-tetramethyl-3,6-dimethyl-3,6-diazaoctane-1,8-diamine (L¹) in ethanol yielded cis-[Ru^III(L¹)Cl₂]⁺, which was isolated as the ClO₄^- salt. The optical spectrum of cis-[Ru^III(L¹)Cl₂]ClO₄ in acetonitrile displays one intense band at 375 nm attributed to a p_π(Cl) → d_π* (Ru) transition. cis.-[Ru^III(L¹)Cl₂]ClO₄ has been characterized by X-ray crystallography: space group P2₁/c, a = 11.716(5), b = 13.089(4), c = 12.981(5) Å, β = 94.28(2)°, Z = 4, and R = 0.076 for 1 913 observed Mo-K_α data. The co-ordination geometry around the metal ion is distorted octahedral with cis arrangement of the two chloride ligands. The average Ru-N and Ru-Cl bond distances are 2.17(1) and 2.345(4) Å, respectively. Treatment of cis-[Ru^III(L¹)Cl₂]ClO₄ with silver(I) p-toluenesulphonate in hot water and then H₂O₂ gave [Ru^VI(L¹)(O)₂]²⁺ isolated as the ClO₄^- salt. [Ru^VI(L¹)(O)₂][ClO₄]₂ is diamagnetic (μ_eff. = 0) and has an intense i.r. band at ca. 850 cm^-1 attributed to ν_asym (Ru=O) stretching. The E_1/2 value of the [Ru^VI(L¹)(O)₂]²⁺/[Ru ^IV(L¹)(O)(H₂O)]²⁺ couple in 0.1 mol dm^-3 CF₃CO₂H is 0.79. V vs. a saturated calomel electrode. The reaction of [Ru^IV(L¹)(O)₂][ClO₄]₂ with styrene produced benzaldehyde.