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

Abstract

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(OAc_0.4/OEt_0.6)]⁺ 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 = –2JS_iS_jconvention) and a S = 1 ground state.