Dinuclear Ruthenium Complexes Containing the Hpbl Ligand: Synthesis, Characterization, Linkage Isomerism, and Epoxidation Catalysis

Three dinucleating
Ru–Cl complexes containing the hexadentate
dinucleating ligand [1,1′-(4-methyl-1H-pyrazole-3,5-diyl)­bis­(1-(pyridin-2-yl)­ethanol)]
(Hpbl) and the meridional 2,2′:6′,2″-terpyridine
ligand (trpy) have been prepared and isolated. These complexes include
{[RuCl­(trpy)]2(μ-pbl-κ-N3O)}+ (1a+), {[RuCl­(trpy)]2(μ-Hpbl-κ-N3O)}2+ (1b2+), and {[RuCl­(trpy)]2(μ-Hpbl-κ-N2O2)}2+ (1c2+) and were characterized by analytic
and spectroscopic techniques. In addition, complexes 1b2+ and 1c2+ were characterized
in the solid state by monocrystal X-ray diffraction analysis. The
coordination versatility of the Hpbl ligand allows the presence of
multiple isomers that can be obtained depending on the Ru oxidation
state and were thoroughly characterized by electrochemical techniques,
namely, cyclic voltammetry and coulometry. Finally, 1a+ and its recently reported mononuclear analogue, in-[RuCl­(Hpbl)­(trpy)]+, have been tested as catalysts
for epoxidation of cis-β-methylstyrene.