Encapsulation by a Chromium(III)-Containing Bicyclic Ligand Cage. Synthesis, Structures, and Physical Properties of Heterometal Complexes Cr^IIIMCr^III[M = (H⁺)₂, Li(I), Mg(II), Cu(II), Ni(II), Ni(IV), Co(III), Fe(II), Fe(III), Mn(II)]

Abstract

Synthesis of linear trinuclear complexes containing the [tris(dimethylglyoximato)-metalate(II)]4- anion as bridging ligand of general formula [LCrIII{μ-(dmg)3M}CrIIIL]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 reactions of the LCr unit with in situ prepared M(dmg)3 n - ions, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane and dmg2- is the dimethylglyoximato dianion. The clathrochelate complexes 1−13 have been characterized on the basis of elemental analysis, mass spectrometry, IR, UV−vis, Mössbauer, and EPR spectroscopies, and variable-temperature (2−295 K) magnetic susceptibility measurements. They are quasi-isostructural 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 single-crystal X-ray crystallography. They crystallize in the monoclinic system, space group C2/c with the following cell parameters: 7, a = 29.029(7) Å, b = 12.239(4) Å, c = 14.850(4) Å, β = 118.90(2)°, Z = 4; 8, a = 32.333(6) Å, b = 8.772(2) Å, c = 16.716(3) Å, β = 109.51(3)°, Z = 4; 11, a = 30.941(6) Å, b = 8.777(2) Å, c = 16.801(3) Å, β = 96.22(3)°, Z = 4. The structures consist of tris(dimethylglyoximato)-bridged CrIIIMIICrIII dications and noncoordinated perchlorate anions, with an intramolecular Cr···Cr distance of ∼7.1 Å. The trinuclear unit Cr−M−Cr is nearly planar exhibiting angles at M in the range 179.0−178.6°, except 7, with a Cr−Cu−Cr angle of 175.1°. Analysis of the susceptibility data indicates the presence of weak to moderate exchange interactions, both ferro- and antiferromagnetic, between the paramagnetic centers. There are indeed two different coupling constants, J (=J 12 = J 23) and J 13, operative in these clathrochelates. J 13 represents the exchange interaction between the two terminal Cr(III) centers separated by a large distance of ∼7.1 Å. An analysis of the interacting magnetic orbitals in complexes containing three metal centers is presented. The cyclic voltammograms of the complexes reveal both oxidation and reduction processes and indicate the formation of the uncommon species such as Cu(III), Ni(III), Ni(IV), and low-spin Fe(III). Liquid secondary ion mass spectrometry (L-SIMS) demonstrates the nonfragile character of the complexes examined, together with their nuclearity.

Asymmetric Heterodinuclear FeIIIMII (M = Zn, Cu, Ni, Fe, Mn), CoIIIFeII and FeIICoIII Species: Synthesis, Structure, Redox Behavior, and Magnetism

“…It is clear from the data in Table 4 (2), and Zn II (1) are distorted from octahedra toward trigonal prisms, as is evident from the twist angles; these distortions can be ascribed to both electronic (LFSE) and size effects, as has been discussed earlier. [9,10,25] Figure 5 displays two perspective views of the cations in 6 and 7 and their atom labeling schemes. Selected bond lengths and angles are listed in Tables 5 and 6.…”

“…The cyclic voltammograms of the complexes reveal both ligand-centered and metal-centered redox processes. Analysis of the susceptibility data indicates the presence of antiferromagnetic exchange interactions that decrease in the following order: Fe III M A M B , [9] M A M B M A , [10] and M A M B M B M A [11] (M A , M B being two different metal ions). In addition, we have synthesized asymmetric heterotrinuclear complexes with cores M A M B M C [12] and butterfly cores [13] (M A ) 2 unit, where L represents the tridentate cyclic amine 1,4,7-trimethyl-1,4,7-triazacyclononane.…”

“…In addition, we have synthesized asymmetric heterotrinuclear complexes with cores M A M B M C [12] and butterfly cores [13] (M A ) 2 unit, where L represents the tridentate cyclic amine 1,4,7-trimethyl-1,4,7-triazacyclononane. [9,10] In this paper, we explore the effects of using Fe III …”

Old ligands with new coordination chemistry: Linear trinuclear mixed oxidation state cobalt(III/II/III) complexes and their mononuclear “ligand” cobalt(III) complexes featuring 2-pyridyloximates

“…A strong band at $845 cm À1 and a medium-intensity band at 558 cm À1 in the IR spectra of 1 and 5b arise [14] from the m 3 (F 1u )[m(PF)] and m 4 (F 1u ) [d(FPF)] vibrations of the uncoordinated O h PF À 6 ion, respectively. Two bands, one medium to strong at 1606-1598 cm À1 and one of variable intensity at 1244-1222 cm À1 , are common in the spectra of 1-4, 5a, 5b and 6 AE 3MeNO 2 ; these bands are assigned [15] to the oximate m(C@N) and m(N-O) modes, respectively, although the higher-wavenumber band may also have an aromatic stretch character. The m(N-O) mode is situated at a lower wavenumber in the spectra of the trinuclear clusters than for their corresponding mononuclear, ''ligand'' cobalt(III) complexes; for example, the m(N-O) band appears at 1232 and 1244 cm À1 in 3 and 4, respectively.…”

Synthesis, characterization and X-ray crystal structures of N-2-pyridinyl carbonyl-2-pyridine carboximidate copper(II) complexes

“…As more potential applications are realized from assemblies of metal ions, the difficulty in controlling the structure of the assemblies becomes apparent. Complexed ligands can aid in the design and synthesis of metal complex assemblies, and many examples have been reported [11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”