Synthesis, structure, reactivity and electrochemistry of cis-dioxoruthenium-(VI) and -(V) complexes containing N,N,N′,N′,3,6-hexamethyl-3,6-diazaoctane-1,8-diamine

Abstract

The complexes cis-[Ru^VILO₂]²⁺, cis-[Ru^VLO₂]⁺ and cis-[Ru^IIL(MeCN)₂]²⁺(L =N,N,N′,N′,3,6-hexamethyl-3,6-diazaoctane-1,8-diamine) have been prepared and their structures determined. The two RuO bonds in cis-[Ru^VILO₂]²⁺ are equivalent [1.795(9)Å] and the O–Ru–O angle is 112.0(4)°. In cis-[Ru^VLO₂]⁺ the two RuO distances are 1.751(3) and 1.756(4)Å, and the O–Ru–O angle is 115.1(2)°. The N(MeCN)–Ru–N(MeCN) angle in cis-[Ru^IIL(MeCN)₂]²⁺ is 86.1(2)°. The cyclic voltammogram of cis-[Ru^VILO₂]²⁺ in acetonitrile exhibits a reversible one-electron Ru^VI–Ru^V couple at 0.53 V vs. Ag–AgNO₃(0.1 mol dm^–3). In aqueous solutions, proton-coupled electron-transfer redox couples are observed. This complex is capable of oxidising a wide variety of organic substrates including 2,3-dimethylbutane and adamantane. Oxidation of saturated alkanes occurred preferentially at the tertiary C–H bond.