A tri-nuclear oxygen centred (salicylaldoximato)copper(II) compound: The preparation and structure of [{{Cu(saloxH)}3O}3H1.5]·Cl4.5·12DMSO·1.83H2O

Reaction of salycilaldoxime (saloxH2) with copper(II) chloride in strongly alkaline methanol yields a sparingly soluble green product which recrystallised from DMSO as a solvate of composition [{{Cu(saloxH)}3O}3H1.5]·Cl4.5·12DMSO·1.83H2O. This has three independent planar, oxygen-centred, triangular cations, [{Cu(saloxH)}3O], in the asymmetric unit. The central oxygen atom is surrounded by three square-planar coordinated copper(II) ions, which are bonded to the central O-atom, the Ophenol and Noximato atoms of one saloxH− chelate and to the Ooximato atom of the adjacent saloxH− ligand. These triangular cations are stacked, with alternating short {2.46(1) or 2.53(1) Å} and long {7.31(1) or 7.05(1) Å} central oxygen separations, with the closer pairs linked by a hydrogen bond. The 4.5 positive charges of the three cations of the asymmetric unit, [{Cu3(saloxH)3(O)1.5(OH)1.5}3)]4.5+ are balanced by 4.5 chloride ions. Two DMSO molecules lie between the wider spaced pairs of triangles, with their oxygen atoms weakly coordinated to copper(II) ions, with 10 further DMSO molecules and water molecules packed around and between the triangular cations.

► Salicyladoxime forms a copper(II) compound with planar, oxygen-centred trinuclear cations.
► These have the composition [{Cu(saloxH)}3O]+, with mono-deprotonated salicyladoxime.
► The triangles are stacked parallel with alternating short and long oxygen–oxygen separations.