Heterobimetallic nickel–sodium and cobalt–sodium complexes of pyridonate ligands

Abstract

Seven new mixed-metal complexes have been prepared and their structures determined. Reaction of anhydrous nickel(II) chloride with Na(xhp) (xhp = 6-methyl- or 6-chloro-2-pyridonate, mhp or chp respectively) produced the discrete polynuclear complexes [Ni₄Na₄(mhp)₁₂(Hmhp)₂] 1 and [Ni₂Na₂(chp)₂(H₂O)(MeCN)₄] 2, depending on the pyridonate derivative used. A closely related complex [Ni₂Na₂(chp)₆(H₂O)₂(MeCN)₄] 3 cocrystallised with 2 from a reaction scheme involving phenylacetate. A polymeric complex [{Ni₂Na₂(chp)₆(H₂O)}_n] 4 can be isolated from a similar reaction to that which gave 2 but by recrystallisation from ethyl acetate rather than the co-ordinating solvent MeCN. The cobalt analogue of 4, [{Co₂Na₂(chp)₆(H₂O)}_n] 5 was also prepared and a closely related cobalt–sodium polymer, [{Co₂Na₂(chp)₆}_n] 6, crystallised from ethyl acetate. A further polymer featuring the mhp ligand, [{Co₂Na₂(mhp)₆(Hmhp)(H₂O)}_n] 7, was produced from reaction of anhydrous cobalt(II) acetate with Na(mhp) followed by recrystallisation from toluene. The structures of the molecular species 1, 2 and 3 can be rationalised as co-ordination of Na by [Ni(xhp)₃]^– ‘complex ligands’ in which the nickel centres are surrounded by three chelating pyridonates. In the polymeric species 4, 5, 6 and 7 the structures can be viewed as involving co-ordination of Na by [M₂(xhp)₆]^2– complex ligands. In 6 the absence of any additional solvent molecules leads to interaction of the sodium site with Cl-donors.