HETEROBIMETALLIC NICKEL-SODIUM AND COBALT-SODIUM COMPLEXES OF PYRIDONATE LIGANDS

Seven new mixed-metal complexes have been prepared and their structure s determined. Reaction of anhydrous nickel(II) chloride with Na(xhp) ( xhp = 6-methyl- or 6-chloro-2-pyridonate, mhp or chp respectively) pro duced the discrete polynuclear complexes [Ni4Na4(mhp)(12)(Hmhp)(2)] 1 and [Ni2Na2(chp)(2)(H2O)(MeCN)(4)] 2, depending on the pyridonate deri vative used. A closely related complex [Ni2Na2(chp)(6)(H2O)(2)(MeCN)(4 )] 3 cocrystallised with 2 from a reaction scheme involving phenylacet ate. 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 cob alt analogue of 4, [{Co2Na2(chp)(6)(H2O)}(n)] 5 was also prepared and a closely related cobalt-sodium polymer, [{Co2Na2(chp)(6)}(n)] 6, crys tallised from ethyl acetate. A further polymer featuring the mhp ligan d, [{Co2Na2(mhp)(6)(Hmhp)(H2O)}(n)] 7, was produced from reaction of a nhydrous 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 lig ands' in which the nickel centres are surrounded by three chelating py ridonates. In the polymeric species 4, 5, 6 and 7 the structures can b e viewed as involving co-ordination of Na by [M-2(xhp)(6)](2-) complex ligands. In 6 the absence of any additional solvent molecules leads t o interaction of the sodium site with Cl-donors.