Understanding the mechanism of H(+)-induced demetalation as a design strategy for robust iron(III) peroxide-activating catalysts.
The FeIII-TAML (tetra-amido macrocyclic ligand) activators 1 (Y = Cl) and 2 (Y = H2O), a (R = Me, X = H), b (Me, Cl), c (Me, MeO), d (Et, Cl), e (F, H), f (F, Cl), are five-coordinated in the solid state (X-ray crystallography) but are six-coordinated species in water with two H2O axial ligands. The first pKa's of aqueous ligands are in the range of 9.5-10.5. The acid-induced demetalation of 2 follows the equation kobs = k1*[H+] + k3*[H+]3. The rate constants k1* and k3* vary by 5 and 11 orders of magnitude depending on the nature of substituents R. The highest stabilization against the demetalation is achieved for R = F.
Ghosh
Anindya
A
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Ryabov
Alexander D
AD
Mayer
Sherry M
SM
Horner
David C
DC
Prasuhn
Duane E
DE
Sen Gupta
Sayam
S
Vuocolo
Leonard
L
Culver
Caleb
C
Hendrich
Michael P
MP
Rickard
Cliffton E F
CE
Norman
Richard E
RE
Horwitz
Colin P
CP
Collins
Terrence J
TJ
D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry* / Q000378:metabolism; D011522:Protons
D005290:Ferric Compounds; D010545:Peroxides; D011522:Protons