Unusual dimer formation of cyclometalated ruthenium NHC p-cymene complexes

Abstract

We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η⁶-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^F₄) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru]⁺[BAr^F₄]⁻. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η⁶-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group “atop” is retained in the bimetallic complexes.