Bis(arene) complexes of Ru II. Synthesis, crystal structure and electrochemical behavior of [bis(η 6- p-isopropyltoluene)Ru][BF 4] 2

Abstract

Cleavage of the chloro-bridged Ru II dimer, [( p-isopropyltoluene)Ru(Cl) 2] 2 with AgBF 4 in acetone and refluxing the product in trifluoroacetic acid with an excess of p-isopropyltoluene leads to the formation of the dicationic bis(arene) Ru II complex, [( p-isopropyltoluene) 2Ru][BF 4] 2, in nearly quantitative yield. Strong upfield shifts are observed in the 13C NMR spectrum of the arene carbon atoms of p-isopropyltoluene following coordination and an investigation of the electrochemistry of this complex shows that it undergoes an irreversible reduction in nitromethane solvent at −0.78 V versus an Ag/AgCl reference electrode. An X-ray crystal structure determination of the complex shows that the complex consists of a Ru II center located between two p-isopropyltoluene ligands that are coordinated in an η 6 manner. The arene rings are separated by a distance of 3.450 Å and are essentially coplanar with a dihedral angle of 178.4°. The crystals are monoclinic, space group P2 1/ n wth lattice constants a = 10.094(2) Å, b = 12.996(3) Å, c = 17.371(3) Å, β = 94.90(1)° and V = 2270.4(8) Å 3. Convergence to conventional R values of R = 0.0711 and R w = 0.0854 with a goodness-of-fit of 1.15 was obtained for 280 variable parameters and 2976 reflections with I > 0σ( I).