The reaction of vitamin B_12a and of cobaloximes with carbon monoxide. Evidence for self-reduction of vitamin B_12a in neutral solution

The reactivity of cobalt(I) complexes containing unsaturated macrocyclic ligands in aqueous solution

“…Value for CoH(l,3,8,10-tetraeneN4) was determined at pH 6.5 only. 6 Determined in the presence of 1 x 10'* M Co(II) substrate, 0.1 Af HC02~i n Ar-purged solutions. "Determined in the presence of 1 X 10"3 M Co(II) substrate, 2 Af 2-propanol, perchloric acid, or 1 mAf phosphate buffer in Ar-purged solutions.…”

“…(A: Reaction of the Co(II) complexes with eaq-occurs at or near the diffusion-controlled limit. The values of k for the Co!,(dieneN4) complexes are independent of pH (6)(7)(8)(9)(10) suggesting that the complexes do not undergo protonationdeprotonation reactions in that pH range; acid-base behavior can affect the value of Ac and is seen in the reactions of the corresponding Co(III) complexes with eaq-.36 Because of the sensitivity of Con(l,3,8,10-tetraeneN4) towards base, all experiments with that complex were performed at pH <7. The reaction of eaq-with Co(II) generates the spectrum of Co(I) directly with no evidence for the initial formation of a Co(II)-coordinated ligand radical species at a time resolution of ~0.1 /¿sec.…”

Electrochemical Behavior of Cobalt-Dimethylglyoxime Complex Co(DMG)2(H2O)2 in the Carbon Dioxide Reduction Process

“…A similar reaction had been described in [9], whose authors studied the reduction of Co(DMG) 2 (ç 2 é) 2 by carbon monoxide in an alkaline environment. Given reaction (4) we deem it possible to draw the conclusion that the anionic form of complex [Co(DMG) 2 (ç 2 é)] -, which forms in the course of the process of dissociation via reaction (4), undergoes oxidation at the potential E , ‡ = -0.49 V (Fig.…”

Development of a hydrogen sulfide end-of-service-life indicator for respirator cartridges using cobinamide

“…Other reducing agents reported to reduce vitamin B 12 and cause similar spectral shifts include fructose [32], sodium borohydride [34], dithiothreitol [33], and sodium formate [34, 35]. Gas phase reducing agents will generally not be present in occupationally-relevant environments, with the possible exception of carbon monoxide, which reacts extremely slowly with vitamin B 12 (Co(II)) [36]. Therefore, carbon monoxide is not likely to cause an interference when using Cbi as the indicating reagent.…”