title: Kinetics and mechanism of the reaction of hydrogen sulfide with diaquacobinamide in aqueous solution.
abstract: We conducted a detailed kinetic study of the reaction of the vitamin B12analog diaquacobinamide ((H2O)2Cbi(III)) with hydrogen sulfide in water from pH 3 to 11. The reaction proceeds in three steps: (i) formation of three different complexes between cobinamide and hydrogen sulfide, viz. (HO-)(HS-)Cbi(III), (H2O)(HS-)Cbi(III), and (HS-)2Cbi(III); (ii) inner-sphere electron transfer (ISET) in the two complexes with one coordinated HS-to form the reduced cobinamide complex [(H)S]Cbi(II); and (iii) addition of a second molecule of hydrogen sulfide to the reduced cobinamide. ISET does not proceed in the (HS-)2Cbi(III) complex. The final products of the reaction between cobinamide and hydrogen sulfide were found to be independent of pH, with the main product being a complex of cobinamide(II) with the anion-radical SSH2-.
authors.affiliation: Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy str. 7, 153000 Ivanovo, Russia ; Department of Chemistry and Pharmacy, University of Erlangen - Nuremberg, Egerland strasse 1, 91058 Erlangen, Germany.
authors.forename: Denis S
authors.initials: DS
authors.lastname: Salnikov
authors.affiliation: Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy str. 7, 153000 Ivanovo, Russia.
authors.forename: Sergei V
authors.initials: SV
authors.lastname: Makarov
authors.affiliation: Department of Chemistry and Pharmacy, University of Erlangen - Nuremberg, Egerland strasse 1, 91058 Erlangen, Germany.
authors.forename: Rudi
authors.initials: R
authors.lastname: van Eldik
authors.affiliation: Department of Food Chemistry, Ivanovo State University of Chemistry and Technology, Sheremetevskiy str. 7, 153000 Ivanovo, Russia.
authors.forename: Polina N
authors.initials: PN
authors.lastname: Kucherenko
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0652, United States.
authors.forename: Gerry R
authors.initials: GR
authors.lastname: Boss
keywords: Cobinamide; Hydrogen sulfide; Kinetics; Reaction mechanisms; Redox chemistry