Chloro-substituted dipicolinate vanadium complexes: synthesis, solution, solid-state, and insulin-enhancing properties.

Three vanadium complexes of chlorodipicolinic acid (4-chloro-2,6-dipicolinic acid) in oxidation states III, IV, and V were prepared and their properties characterized across the oxidation states. In addition, the series of hydroxylamido, methylhydroxylamido, dimethylhydroxylamido, and diethylhydroxylamido complexes were prepared from the chlorodipicolinato dioxovanadium(V) complex. The vanadium(V) compounds were characterized in solution by (51)V and (1)H NMR and in the solid-state by X-ray diffraction and (51)V NMR.

Size discrimination in the coordination chemistry of an isoindoline pincer ligand with CdII and ZnII.

The reactions of Cd2+ and Zn2+ with the pyridine-arm isoindoline ligand 4'-MeLH = 1,3-bis[2-(4-methylpyridyl)imino]isoindoline produced the series of octahedrally coordinated complexes M(4'-MeL)2, [M(4'-MeLH)2]2+, and [M(4'-MeL)(4'-MeLH)]+. The complexes M(4'-MeL)2 resulted from reactions of the respective metal perchlorates with deprotonated ligand, whereas the complexes [M(4'-MeLH)2](ClO4)2 resulted from reactions with ligand in the absence of added base. The mixed-ligand complexes [M(4'-MeL)(4'-MeLH)]+ were generated in solution by reactions of equimolar quantities of M(4'-MeL)2 and [M(4'-MeLH)2]2+.

Fluxional behavior of a cadmium zwitterion complex: proton transport and tautomerism in methylene chloride solution.

The synthesis and structure of the tautomeric Cd(II) isoindoline zwitterion coordination compound [Cd(4'-MeLH)(NO(3))(2)].CH(3)OH (4'-MeLH = 1,3-bis[2-(4-methylpyridyl)imino]isoindoline) are reported. In methylene chloride solution, tautomer interconversion occurs as the N-H proton moves between the identical imine nitrogen atoms.

Syntheses and structures of isoindoline complexes of Zn(II) and Cu(II): an unexpected trinuclear Zn(II) complex.

Deprotonation of the tridentate isoindoline ligand 1,3-bis[2-(4-methylpyridyl)imino]-isoindoline, 4'-MeLH, and reaction with hydrated zinc(II) perchlorate produces an unexpected trinuclear Zn(II) complex, [Zn(3)(4'-MeL)(4)](ClO(4))(2).5H(2)O (1), whereas reaction with hydrated copper(II) perchlorate in methanol produces the expected mononuclear product, [Cu(4'-MeL)(H(2)O)(2)]ClO(4) (2). X-ray diffraction shows that the trinuclear Zn(II) complex (1) contains a linear zinc backbone, and the arrangement of ligands about the outer chiral zinc(II) atoms is helical.

4-Hydroxypyridine-2,6-dicarboxylatodioxovanadate(V) complexes: solid state and aqueous chemistry.

The aqueous solution and solid state properties of (4-hydroxypyridine-2,6-dicarboxylato)dioxovanadate(V) (also referred to as (4-hydroxydipicolinato)dioxovanadate(V) or (chelidamato)dioxovanadate(V) and abbreviated [VO(2)(dipic-OH)](-)) were investigated. By using (1)H, (13)C, (17)O, and (51)V NMR 1D and 2D spectroscopy, the species present in solution, together with pK(a) values, equilibrium constants, and labilities, were characterized. The complex is most stable at acidic pH down to pH 1 where it is protonated.

Cobalt(II) and cobalt(III) dipicolinate complexes: solid state, solution, and in vivo insulin-like properties.

The synthesis and characterization of Co(II) and Co(III) 2,6-pyridinedicarboxylate (dipic(2-)) complexes are reported. Solid-state X-ray characterizations were performed on [Co(H(2)dipic)(dipic)].3H(2)O and [Co(dipic)(mu-dipic)Co(H(2)O)(5)].

Synthesis and Structure of an Air-Stable, Free-Radical Cobalt(III) Semiquinone Complex.

The air-stable, free-radical, low-spin Co(III) complex, (Bu(4)N)(2) [3,5-Co(DBSQ)(CN)(4)].(1)/(2)H(2)O.(1)/(4)CH(2)Cl(2) (1), where 3,5-DBSQ is the semiquinone anion derived from the one-electron reduction of 3,5-di-tert-butyl-1,2-benzoquinone, has been synthesized by the reaction of the cobalt(II) tetramer [Co(3,5-DBSQ)(2)](4) with Bu(4)NCN in THF.