Anilinopyridinate-supported Ru₂^x+ (x = 5 or 6) paddlewheel complexes with labile axial ligands

Five new metal–metal bonded Ru₂ compounds are presented and discussed: Ru₂(ap)₄ONO₂ (2), [Ru₂(ap)₄NCMe][BF₄] (3), Ru₂(ap)₄FBF₃ (4), Ru₂(ap)₄OTf (5), and [Ru₂(ap)₄OTf][Ag(OTf)₂] (6) (ap = 2-anilinopyridinate). All compounds have a (4,0) arrangement of the ap ligands about the Ru–Ru bond and contain one sterically blocked axial site and one site containing a labile ligand. These compounds display some of the shortest Ru–Ru distances known for this class of compounds. We demonstrate a reversible interconversion between compounds 3 and 4 as the MeCN and BF₄⁻ ligands are readily displaced. Despite the presence of labile axial ligands, compounds 2–5 remain high spin with an S = 3/2 ground state as determined by EPR spectroscopy.