Oxygenated Cobalt Complexes with Simple Tetraazamacrocyclic Ligands
Titel:
Oxygenated Cobalt Complexes with Simple Tetraazamacrocyclic Ligands
Auteur:
Yatsimirskii, K. B. Bratushko, Yulia I. Kondratjuk, A. B.
Verschenen in:
Journal of coordination chemistry
Paginering:
Jaargang 23 (1991) nr. 1-4 pagina's 335-343
Jaar:
1991-06-01
Inhoud:
Binuclear oxygenated cobalt complexes with 5,7,12,14-tetramethy I-1,4,8,II-tetraazacyclotetradeca-4,II -diene (Me4[14]dieneN4) and 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclotetradeca-4,11 -diene (Me6[14]dieneN4) with axial ligands (NCO-, NCS-, NCSe-, N-3, OH-, NO-2, ON-C(CN)2-, Im) have been isolated and characterised by physical and chemical methods, including derivatography, electronic, IR and X-ray photoelectron spectroscopy, magnetic measurements and EPR. The electronic structure of the cobalt ion-dioxygen fragment conforms to the scheme Co(III)-O2-Co(III). The coordinated dioxygen species is activated owing to the transfer of an appreciable electron density to it. Irreversible oxidation in aqueous solution is illustrated by [μO2{Co(Me4[14]dieneN4)(H2O)}2](CIO4)4. Activation parameters for this process are E* = 54 ± 4 kJ mol-1 and ΔS* = -140 ± 16 J mol K-1. A possible mechanism is proposed.