Unusual dimer formation of cyclometalated ruthenium NHC p-cymene complexes.

We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η(6)-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAr(F)4) to form dinuclear complexes of the general structure Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)RuBAr(F)4. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η(6)-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group "atop" is retained in the bimetallic complexes.