Preparation and Resolution of a Series of Cobalt(III) Complexes Containing 2,2′-Biimidazole and Ethylenediamine

Abstract

A new series of cobalt(III) complexes of the type [Co(H2biim)n(en)3−n]3+ (H2biim = 2,2′-biimidazole; n = 1—3) was obtained. All of the complexes were resolved into their antipodes by SP-Sephadex column chromatography. The absorption, circular dichroism, and 1H NMR spectra of the complexes in aqueous solutions were dependent on the pH due to deprotonation of the imino protons of H2biim. The pKa1 and pKa2 values for [Co(H2biim)(en)2]3+ were obtained as 5.9 and 9.9, respectively, from the absorption spectra in aqueous solutions. The optically active deprotonated complexes, (−)589-[Co(Hbiim)3]·2H2O and (−)589-Ba1.5[Co(biim)3]·2H2O, were also isolated from weakly and strongly basic aqueous solutions, respectively, of (−)589-[Co(H2biim)3](NO3)3·H2O.

Crucial Influence of Solvent and Chirality—The Formation of Helices and Three-Dimensional Nets by Hydrogen-Bonded Biimidazolate Complexes

“…[Co(2,2'-biimidazole) 3 ][NO 3 ] 3 (3) and the precursor [D-Co(Hbiim) 3 ]´2 H 2 O were prepared according to the literature. [28] IR spectra were recorded in the range 4000 ± 200 cm À1 with a Nicolet Magna IR 560 spectrometer. Thermogravimetry measurements were made on a Mettler instrument.…”

“…A helix: Recrystallisation in ethanol of the solid compound obtained by deprotonation of [D-Co(2,2'-biimidazole) 3 ]-[NO 3 ] 3 by ammonia in water, [28] gave air-sensitive orange crystals of compound 4. However, the highly porous chiral (10,3)-a net was not formed, instead each cobalt complex hydrogen bonds with only two of the three biimidazoles giving a helix structure ( Figure 6).…”

Anomalous Enhancement of Proton Conductivity for Water Molecular Clusters Stabilized in Interstitial Spaces of Porous Molecular Crystals

“…Preparation of {[Co III (H 2 bim) 3 ](TATC)⋅7 H 2 O} n (2) : [Co III (H 2 bim) 3 ](NO 3 ) 3 39 (0.020 g, 3.1 mmol) and K 3 TATC40 (0.010 g, 3.1 mmol) were allowed to slowly diffuse together in H 2 O (10 mL) for 3 days, resulting in the deposition of orange rectangular crystals. Yield: 6.80 mg (27.7 %); elemental analysis calcd (%) for CoC 24 H 32 N 15 O 13 : C 36.14, H 4.04, N 26.34, Co 7.39; found: C 36.28, H 3.73, N 26.06, Co 6.72; IR (KBr): 3136, 1637, 1545, 1402, 1300, 1194, 1142, 756, 735 cm −1 .…”

Computational Investigations on the General Reaction Profile and Diastereoselectivity in Sulfur Ylide Promoted Aziridination

“…A helix : Recrystallisation in ethanol of the solid compound obtained by deprotonation of [ Δ ‐Co(2,2′‐biimidazole) 3 ][NO 3 ] 3 by ammonia in water,28 gave air‐sensitive orange crystals of compound 4 . However, the highly porous chiral (10,3)‐a net was not formed, instead each cobalt complex hydrogen bonds with only two of the three biimidazoles giving a helix structure (Figure 6).…”

“…General : All reagents were purchased from commercial sources and used without further purification. [Co(2,2′‐biimidazole) 3 ][NO 3 ] 3 ( 3 ) and the precursor [ Δ ‐Co(Hbiim) 3 ]⋅2 H 2 O were prepared according to the literature 28. IR spectra were recorded in the range 4000–200 cm −1 with a Nicolet Magna IR 560 spectrometer.…”