Abstract
In aqueous solution [Fe 2(μ-O)(phen) 4(H 2O) 2] 4+ ( 1, phen = 1,10-phenanthroline) equilibrates with its conjugate bases [Fe 2(μ-O)(phen) 4(H 2O)(OH)] 3+ ( 2) and [Fe 2(μ-O)(phen) 4(OH) 2] 2+ ( 3). In the presence of excess phen and in the pH range 2.5–5.5, the dimer quantitatively oxidizes pyruvic acid to acetic acid and carbon dioxide, the end iron species being ferroin, [Fe(phen) 3] 2+. The observed reaction rate shows a bell-shaped curve as pH increases, but is independent of added phen. Kinetic analysis shows that ( 3) is non-reactive and ( 1) has much higher reactivity than ( 2) in oxidizing pyruvic acid. The basicity of the bridging oxygen increases with deprotonation of the aqua ligands. The reaction rate decreases significantly in media enriched with D 2O in comparison to that in H 2O, with a greater retardation at higher pH, suggesting the occurrence of proton coupled electron transfer (PCET; 1e, 1H +), which possibly drags the energetically unfavorable reaction to completion in presence of excess phen.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call