H. Kido, Kazuo Saito
Feb 1, 1980
Citations
0
Influential Citations
11
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
Tris(acetylacetonato[2-14C])iron(III) undergoes ligand exchange in acetylacetone at 4–16 °C without side reactions. The exchange rate is expressed by Rate=(ka+kb[H2O])[complex]([complex]≈0.01 M, [H2O]≈0.05 M), and the rate constant (10.2 °C) and activation parameters are ka=(8.9±1.2)×10−4 s−1, ΔH\eweq=14.4±0.9 kcal mol−1, ΔS\eweq=−22±3 cal K−1 mol−1 and kb=(2.22±0.20)×10−2 M−1 s−1, ΔH\eweq=16.9±0.4 kcal mol−1, ΔS\eweq=−6.1±1.3 cal K−1 mol−1 (1 cal=4.18 J, 1 M=1 mol dm−3). No deuterium isotope effect on the rate. The rate-determining steps seem to correspond to the formation of intermediates containing a one-ended acac− and an Hacac molecule (the ka path), and the anion and a water molecule (the kb path), by the SN2 mechanism.