Preparation of a dicationic, p-cymene ruthenium(II) dimer, [(p-cymene)Ru(µ-Cl)(P{OCH₂}₃CEt)]₂²⁺: structure, characterization and reactivity

Reaction of (p-cymene)RuCl₂(P{OCH₂}₃CEt) (P{OCH₂}₃CEt = 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane) with silver tetrakis[(3,5-trifluoromethyl)phenyl]borate (Ag[BArF′]) in the presence of acetonitrile produces the monomeric, cationic, acetonitrile ruthenium(II) compound, [(p-cymene)RuCl(P{OCH₂}₃CEt)(NCMe)][BArF′] (1), in near quantitative yields (97%). Chloroform solutions of 1 cause precipitation of the binuclear, dicationic ruthenium(II) dimer complex, [(p-cymene)Ru(µ-Cl(P{OCH₂}₃CEt)]₂[BArF′]₂ (2), with bridging chloride ligands (73%). Complex 2 can be readily converted back to 1 by treatment with acetonitrile. Complexes 1 and 2 were characterized by ¹H, ¹³C{¹H}, ³¹P{¹H}, ¹⁹F{¹H} nuclear magnetic resonance spectroscopy and infrared spectroscopy. Complex 2 was also characterized by single crystal X-ray crystallography, which revealed a rhomboid Ru₂Cl₂ core. The two ruthenium ions in 2 are displaced at 3.668 Å, which precludes Ru–Ru bonding. To our knowledge, this is the first cymene ruthenium(II) dimeric complex with bridging halide ligands supported by a monodentate phosphite ligand.