Unexpected chlorination of a pyrazole ligand. Structural characterisation of a new binuclear Cu(II) complex

Crystallisation of Cu(HL1)2Cl2·EtOH (HL1=3-phenyl-5-(6-methyl-2-pyridyl)pyrazole) in DMF affords [Cu2(ClL1)2Cl2(DMF)2], where the C-chlorination of the pyrazolyl ring and the formation of a dinuclear compound is observed. The deprotonated pyrazolyl ligands have three co-ordination positions (two pyrazole nitrogens and one pyridine nitrogen) and simultaneously act as chelate and bridging ligands.