A binuclear ruthenium(II) complex of 2,2′:3′,2″:6″,2‴-quaterpyridine containing RuN5Cl and cyclometallated RuN5C fragments linked by a bridging (N,C-donor) pyridyl residue

Abstract

Reaction of the binucleating compound 2,2′:3′,2″:6″,2‴-quaterpyridine (HL), which normally acts as a bis(bipyridyl) ligand with two N,N-bidentate binding sites, with 2 equivalents of [Ru(terpy)Cl₃](terpy = 2,2′:6′,2″-terpyridine) in the presence of N-methylmorpholine afforded the unusual binuclear complex [Cl(terpy)Ru(µ-L)Ru(terpy)][PF₆]₂1 in which L is acting as an N,N-bidentate donor to one metal and an N,N,C-cyclometallating terdentate donor to the other. One of the pyridyl residues is therefore acting as an N-donor to one ruthenium(II) centre and a C-donor to the other via the C⁴ position. Complex 1was fully characterised by elemental analysis, ¹H NMR (including correlation) and fast-atom bombardment mass spectrometry. Cyclic and square-wave voltammetry shows two reversible one-electron metal-centred oxidations at potentials consistent with the metal co-ordination environments, and the electronic spectrum is also consistent with the complex formulation.