6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The diruthenium(I,I) complexes shown in the Scheme have a head-to-tail arrangement of the two pyridonate ligands in the solid state. In solution, a temperature- and solvent-dependent equilibrium between head-to-tail and head-to-head complexes exists which was studied by NMR spectroscopy. When L is an imidazolylidene ligand, a stable head-to-head arrangement is found where only the O,O-substituted Ru atom bears a carbene ligand.