Syntheses, crystal structures and properties of mononuclear chromium(III) and dinuclear vanadium(III) and copper(II) complexes with a bis-bipyridyl ligand †

The reaction between [VCl3(thf)3] and the bis-bidentate ligand L [L = 1,2-bis(2,2′-bipyridyl-6-yl)ethane] in MeOH gave the oxo-bridged dinuclear complex [V2OCl2L2]Cl2 1, which contains a near linear V–O–V unit. Reaction of CrCl3·6H2O with L in refluxing MeOH gave mononuclear trans-[CrCl2L]Cl 2 with the ligand L co-ordinated equatorially. Equimolar reaction of L with [Cu2(OAc)4(H2O)2] in EtOH followed by addition of NaClO4 yielded the dinuclear complex [Cu2(OAc)2.4(OEt)0.6L]ClO4 3, whose cation contains a [Cu2(OAc)2(OAc0.4/OEt0.6)]+ core, with two bridging OAc– ligands and a bridging oxygen atom shared by disordered OEt– and monodentate OAc– ligands. The analogous reaction with addition of HBF4 gave [Cu2F(OAc)2L]BF4 4, which contains two bridging OAc– ligands and a bridging F– atom. Compound 1 shows strong ferromagnetic coupling between vanadium(III) ions with J > 100 cm–1 resulting in only the S = 2 ground state being populated, whereas 4 shows weak ferromagnetic coupling, J ≈ +8 cm–1 (H = –2JSiSjconvention) and a S = 1 ground state.