Kinetic studies on the reaction of NO with iron(II) complexes using low temperature stopped-flow techniques

Specht, Pascal; Ossberger, Martin; Kluefers, Peter und Schindler, Siegfried (2020): Kinetic studies on the reaction of NO with iron(II) complexes using low temperature stopped-flow techniques. In: Dalton Transactions, Bd. 49, Nr. 27: S. 9480-9486

Abstract

Low temperature stopped-flow techniques were used to investigate the reaction of three different iron(ii) complexes with nitrogen monoxide. The kinetic studies allowed calculation of the activation parameters from the corresponding Eyring plots for all three systems. The reaction of iron(ii) chloride with NO leading to the formation of MNIC(mononitrosyl-iron-complex) and DNIC (dinitrosyl-iron-complex) led to activation parameters of Delta H-double dagger= 55.4 +/- 0.4 kJ mol(-1)and Delta S-double dagger= 13 +/- 2 J K(-1)mol(-1) for MNIC and Delta H-double dagger= 32 +/- 6 kJ mol(-1)and Delta S-double dagger= -193 +/- 21 J K(-1)mol(-1) for DNIC. Formation of MNIC turned out to be much faster in comparison with DNIC. In contrast, activation parameters for the formation of monoculear [Fe(bztpen)(NO)](OTf)(2)(bztpen =N-benzyl-N,N ',N '-tris(2-pyridylmethyl)-ethylenediamine) Delta H-double dagger= 17.8 +/- 0.8 kJ mol(-1)and Delta S-double dagger= -181 +/- 3 J K(-1)mol(-1) supported an associative mechanism. Interestingly, [Fe(bztpen)(CH3CN)](OTf)(2) does not react with dioxygen at all. Furthermore, activation parameters of Delta H-double dagger= 37.7 +/- 0.7 kJ mol(-1) and Delta S-double dagger= -66 +/- 3 J K(-1)mol(-1)were obtained for the reaction of NO with the dinuclear iron(II) H-HPTB complex (H-HPTB =N,N,N ',N '-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane), [Fe-2(H-HPTB)(Cl)(3)]. The kinetic data allowed postulation of the mechanisms for all of these reactions.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Chemie und Pharmazie > Department Chemie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 1477-9226
• Sprache: Englisch