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-[RuIII(L1)Cl2]ClO4

Abstract

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(RuO) stretching. The E_½ 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.