Cationic assembly of metal complex aggregates:: Structural diversity, solution stability, and magnetic properties

The tetradentate imino-carboxylate ligand [L](2-) chelates the equatorial sites of Ni-II to give the complex [Ni(L)(MeOH)(2)] in which a Ni-II center is bound in an octahedral coordination environment with MeOH ligands occupying the axial sites. Lanthanide (Ln) and Group 11 metal ions (M) template the aggregation of six [Ni(L)] fragments into the octahedral cage aggregates {M[Ni(L)](6)}(x+) (1: M = Sr-II; x= 2, 2: M = Ball; x = 2, 3: M = La-III; x = 3, 4: M = Ce-III; x = 3, 5: M = Pr-III; x = 3, and 6: M = Nd-III; x = 3). In the presence of Group I cations, however, aggregates composed of the alkali metal-oxide cations template various cage compounds. Thus, Na+ forms the trigonal bipyramidal [Na5O](3+) core within a tricapped trigonal prismatic [Ni(L)](9) aggregate to give {(Na5O)subset of[Ni(L)](9)(MeOH)(3)}(BF4)(2)(OHCH3OH)-O-.-C-., 7. Li+ and Na+ together form a mixed Li+/Na+ core comprising distorted trigonal bipyramidal [Na3Li2O](3+) within an approximately anti-square prismatic [Ni(L)](8) cage in {(Na3Li2O)subset of[Ni(L)](8)(CH3OH)(1.3)(BF4)(0.7)}(BF4)(2.3.)(CH3OH)(2.75)(.)(C4H10O)(0.5), 8, while in the presence of Li+, a tetrahedral [Li4O](2+) core within a hexanuclear open cage [Ni(L)](6) in {(Li4O)subset of[Ni(L)](6)(CH3OH)(3)}2ClO(4).1.85CH(3)OH, 9, is produced. In the presence of H2O, the Cs+ cation induces the aggregation of the [Ni(L)(H2O)(2)] monomer to give the cluster Cs-2[Ni(L)(H2O)(2)](6).2l-4CH(3)OH.5.25H(2)O, 10. Analysis by electronic spectroscopy and mass spectrometry indicates that in solution the trend in stability follows the order 1-6 > 7 > 8 similar to 9. Magnetic susceptibility data indicate that there is net antiferromagnetic exchange between magnetic centers within the cages.