ENCAPSULATION BY A CHROMIUM(III)-CONTAINING BICYCLIC LIGAND CAGE - SYNTHESIS, STRUCTURES, AND PHYSICAL-PROPERTIES OF HETEROMETAL COMPLEXES CRIIIMCRIII [M=(H+)(2), LI(I), MG(II), CU(II), NI(II), NI(IV), CO(III), FE(II), FE(III), MN(II)]

Synthesis of linear trinuclear complexes containing the [tris(dimethyl glyoximato)-metalate(II)(4-) anion as bridging ligand of general formu la [LCrIII{mu-(dmg)(3)M}(CrL)-L-III](1+/2+/3+/4+) as perchlorate salts , where M = (H+)(2) (1 and 2), absent (3), (H+)(4) (4), Li(I) (5), Mg( II) (6), Cu(II) (7), Ni(II) (8), Ni(IV) (9), Co(III) (10), Fe(II) (11) , Fe(III) (12) and Mn(II) (13), has been achieved by stepwise reaction s of the LCr unit with in situ prepared M(dmg)(3)(n-) ions, where L re presents 1,4,7-trimethyl-1,4,7-triazacyclononane and dmg(2-) is the di methylglyoximato dianion. The clathrochelate complexes 1-13 have been characterized on the basis of elemental analysis, mass spectrometry, I R, UV-vis, Mossbauer, and EPR spectroscopies, and variable-temperature (2-295 K) magnetic susceptibility measurements. They are quasi-isostr uctural with the terminal chromium(III) ions in a distorted octahedral environment, CrN3O3, and the central metal ions M are six-coordinate, mostly trigonal prismatic, with the MN6 core. The crystal structures of the perchlorate salts of 7, 8, and 11 have been determined by singl e-crystal X-ray crystallography. They crystallize in the monoclinic sy stem, space group C2/c with the following cell parameters: 7, a = 29.0 29(7) Angstrom, b = 12.239(4) Angstrom, c = 14.850(4) Angstrom, beta = 118.90(2)degrees, Z = 4; 8, a = 32.333(6) Angstrom, b = 8.772(2) Angs trom, c = 16.716(3) Angstrom, beta = 109.51(3)degrees, Z = 4; 11, a = 30.941(6) Angstrom, b = 8.777(2) Angstrom, c = 16.801(3) Angstrom, bet a = 96.22(3)degrees, Z = 4. The structures consist of tris(dimethylgly oximato)-bridged (CrMnCrIII)-Mn-III-Cr-II dications and noncoordinated perchlorate anions, with an intramolecular Cr ... Cr distance of simi lar to 7.1 Angstrom. The trinuclear unit Cr-M-Cr is nearly planar exhi biting angles at M in the range 179.0-178.6 degrees, except 7, with a Cr-Cu-Cr angle of 175.1 degrees. Analysis of the susceptibility data i ndicates the presence of weak to moderate exchange interactions, both ferro-and antiferromagnetic, between the paramagnetic centers. There a re indeed two different coupling constants, J (=J(12) = J(23)) and J(1 3), operative in these clathrochelates. J(13) represents the exchange interaction between the two terminal Cr(III) centers separated by a la rge distance of similar to 7.1 Angstrom. An analysis of the interactin g magnetic orbitals in complexes containing three metal centers is pre sented. The cyclic voltammograms of the complexes reveal both oxidatio n and reduction processes and indicate the formation of the uncommon s pecies such as Cu(III), Ni(III), Ni(IV), and low-spin Fe(III). Liquid secondary ion mass spectrometry (L-SIMS) demonstrates the nonfragile c haracter of the complexes examined, together with their nuclearity.