Synthesis, electrochemistry and X-ray crystal structure of cis-[RuIIIL1(Cl)(H2O)][ClO4]2·2H2O [L1=N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine]; electrochemical oxidation of alcohols and tetrahydrofuran by cis-[RuVL1(Cl)O]2+
Abstract
Reaction of K2[RuCl5(H2O)] with N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine (L1) in ethanol gave cis-[RuIIIL1Cl2]+ and then cis-[RuIIIL1(Cl)(H2O)]2+ upon reaction with AgI in water. The structure of cis-[RuIIIL1(Cl)(H2O)][ClO4]2·2H2O has been established by X-ray crystallography: space group Pbca, a= 10.863(1), b= 21.548(2), c= 21.912(2)Å. The measured Ru-Cl and Ru-OH2 distances are 2.307(4)Å and 2.070(9)Å respectively. A cyclic voltammogram of cis-[RuIIIL1(Cl)-(H2O)]2+ in 0.1 mol dm–3 CF3CO2H shows three reversible/quasi-reversible couples at 1.29, 0.93 and 0.23 V vs. saturated calomel electrode assigned to the couples RuV-RuIV, RuIV-RuIII and RuIII-RuII. The complex cis-[RuIIIL1(Cl)(H2O)]2+ is an active catalyst for the electrochemical oxidation of alcohols and tetrahydrofuran. The second-order rate constant for the oxidation of benzyl alcohol by electrochemically generated cis-[RuVL1(Cl)O]2+ is estimated to be 8.4 × 104 dm3 mol–1 s–1.