Hexa-, hepta- and dodeca-nuclear nickel(II) complexes of three Schiff-base ligands derived from 1,4-diformyl-2,3-dihydroxybenzene.
Three new closely-related diimine ligands, H(4), H(4) and H(4), were prepared by the condensation of 1,4-diformyl-2,3-dihydroxybenzene () with two equivalents of 2-aminoethanol, 3-aminopropanol or 2-aminophenol, respectively. Three polynuclear complexes, [Ni(II)(7)(H(2))(4)(OAc)(6)(H(2)O)(2)].5H(2)O (.5H(2)O), [Ni(II)(6)(H(2))(2)(OAc)(6)(micro-OMe)(2)(H(2)O)(2)].5H(2)O (.5H(2)O) and [Ni(II)(12)()(6)(MeOH)(7)(H(2)O)(3)].4H(2)O (.4H(2)O), were prepared by reaction of the appropriate ligand with 1.50/1.75, 1.75/3.00 or 2.00 equivalents, respectively, of nickel(II) acetate tetrahydrate, in methanol. The crystal structures of these complexes are very different to one another, despite what initially appear to be relatively minor ligand modifications. While [Ni(II)(7)(H(2))(4)(OAc)(6)(MeOH)(2)].7MeOH.4H(2)O possesses C(2) symmetry and has a 4:7 L:M ratio, [Ni(II)(6)(H(2))(2)(OAc)(6)(micro-OMe)(2)(MeOH)(2)].0.5MeOH.0.5H(2)O.Et(2)O and [Ni(II)(12)()(6)(MeOH)(6.5)(H(2)O)(3.5)].solvent have no internal symmetry and have L:M ratios of 2:6 and 6:12, respectively. Two of the four ligands in [Ni(II)(7)(H(2))(4)(OAc)(6)(MeOH)(2)] are in similar planes, whilst the two remaining ligands are near perpendicular to these planes. The six ligands in [Ni(II)(12)()(6)(MeOH)(6.5)(H(2)O)(3.5)] adopt an offset grid-like arrangement with eight of the twelve metal ions at the intersections of the perpendicular, offset, ligands. In contrast, [Ni(II)(6)(H(2))(2)(OAc)(6)(micro-OMe)(2)(MeOH)(2)] features an [Ni(II)(4)(OR)(4)] cubane core with wing tips of the remaining two nickel(II) ions. All three complexes were subsequently prepared in stoichiometric syntheses, in yields of 50% (.5H(2)O), 48% (.5H(2)O) and 62% (.4H(2)O). The magnetic properties of .5H(2)O, .5H(2)O, .4H(2)O are consistent with intra-complex antiferromagnetic coupling dominating overall, and therefore all three complexes display low spin ground states.
Feltham
Humphrey L C
HL
Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
Clérac
Rodolphe
R
Brooker
Sally
S