Boron-capped hexachlorine-containing cobalt(II) clathrochelates were prepared by means of template condensation of dichloroglyoxime (Cl 2 GmH 2 ) with boron-containing Lewis acids on a cobalt(II) ion matrix. The nucleophilic substitution of the reactive chlorine atoms of these macrobicyclic tris-dioximates with thiolate anions gave the hexasulfide cobalt(II) and dodecasulfide CO III CO II CO III mono- and bis-clathrochelates. The treatment of the hexachlorine-containing cobalt(II) precursors with primary aliphatic amines afforded hexa-amine cobalt(III) clathrochelates. The reduction of these precursors led to the clathrochelate [Co(Cl 2 Gm) 3 (BR) 2 ]- anions, which were isolated as the salts with bulky organic cations. The relative stability of these cobalt(I) complexes accounted for a strong electronic effect of six electron-withdrawing ribbed chlorine substituents. Superconducting quantum interference device (SQUID) magnetometry, EPR, and multi-temperature X-ray diffraction data showed that the cobalt(II) clathrochelates undergo gradual and incomplete ½ ↔ 3/2 spin transition. The Jahn-Teller distortion of the low-spin encapsulated cobalt(II) ion causes its shift in the direction of one of the three chelate α-dioximate fragments. The anisotropic displacement parameters were used to estimate the ordering of the molecular species, and the superposition of two Jahn-Teller distorted structures was found in a crystal. The cyclic voltammetry (CV) data showed the influence of the substituents in α-dioximate fragments on the redox potentials of an encapsulated cobalt ion. The electron-withdrawing ribbed substituents stabilize the cobalt(I) oxidation state of this ion because of electron-density delocalization on their ribbed substituents, whereas the electron-donating amine groups stabilize the cobalt(III) oxidation state.

Tris-Dioximate Cobalt(I,II,III) Clathrochelates: Stabilization of Different Oxidation and Spin States of an Encapsulated Metal Ion by Ribbed Functionalization

Monoribbed-functionalized (i.e. functionalization of only one of the three α-dioximate fragments) clathrochelate iron(II) tris-dioximates have been synthesized starting from the dichloride precursor FeBd2(Cl2Gm)(BF)2 (where Bd2− and Cl2Gm2− are α-benzyldioxime and dichloroglyoxime dianions, respectively), obtained by condensation of the macrocyclic iron(II) bis-α-benzyldioximate [FeBd2(BF2)2(MeCN)2] with H2Cl2Gm. Thioalkyl, alkylamine, oxo- and azaoxocrown ether clathrochelates, as well as the bis-clathrochelate with a 1,5-diaminopentane bridging fragment, have been characterized using elemental analysis, PD mass, IR, UV-vis, 57Fe Mossbauer and 1H, 13C and 11B NMR spectroscopies, and X-ray crystallography [for the FeBd2(Cl2Gm)(BF)2·2C6H6,
FeBd2{(Et2N)ClGm}(BF)2·C6H6 and FeBd2{(MeS)2Gm}(BF)2 complexes]. Configurations intermediate between trigonal prismatic and trigonal antiprismatic have been deduced for the low-spin iron(II) ion coordination polyhedra of the monoribbed-functionalized clathrochelates using 57Fe Mossbauer parameters. The products of de- and re-alkylation reactions of the methylthiol complex FeBd2{(MeS)2Gm}(BF)2 have been identified. The correlation of E1/2 values for Fe3+/Fe2+ couples (from cyclic voltammograms) with Hammett σpara constants for substituents in the functionalized fragments is discussed.

Clathrochelate monoribbed-functionalized iron(II) α-dioximates: synthetic pathways and structural and electrochemical features

Distortions from trigonal prismatic geometry for several structurally characterized clathrochelate complexes: significance of π-backbonding on clathrochelate coordination geometry

Template synthesis, structure and unusual series of phase transitions in clathrochelate iron(II) α-dioximates and oximehydrazonates formed by capping with functionalized boron-containing agents

Chloride ion-aided one-pot template self-assembly of a mixed pyrazoloxime ligand with phenylboronic acid on a corresponding metal(II) ion as a matrix afforded the first boron-capped zinc, cobalt, iron, and manganese pseudoclathrochelate tris-pyrazoloximates. The presence of a pseudocross-linking hydrogen-bonded chloride ion is critical for their formation, as the same chloride-capped complexes were isolated even in the presence of large excesses of bromide and iodide ions. As revealed by X-ray diffraction, all complexes are capped with a chloride ion via three N–H···Cl hydrogen bonds that stabilize their pseudomacrobicyclic frameworks. The MN6 coordination polyhedra possess a distorted trigonal prismatic geometry, with the distortion angles φ between their nonequivalent N3 bases of approximately 0°. Temperature dependences of the effective magnetic moment for the paramagnetic complexes showed the encapsulated metal(II) ions to be in a high-spin state in the temperature range of 2–300 K. In the case of the...

Chloride Ion-Aided Self-Assembly of Pseudoclathrochelate Metal Tris-pyrazoloximates

The synthesis of an extended series of mononuclear and binuclear iron complexes based on oxime-hydrazone ligands is reported. In addition, the syntheses of the first examples of cobalt clathrochelate complexes utilizing oxime- hydrazone ligands are presented. The structures of the new complexes are established through elemental analysis and NMR spectral characterization. Cyclic voltammotric and electrolytic studies illustrate that the oxidation of the iron to the 3+ state does not produce a stable complex; however, the cobalt complexes are shown to be stable in both the +2 and the +3 oxidation states

Todd A. Bish

Papers

Synthesis and characterization of iron and cobalt clathrochelate complexes derived from oxime-hydrazone ligands