15391-24-9Relevant academic research and scientific papers
Hydrogen-Bonding Interactions Involving Metal-Bound Dioxygen
Drago, Russell S.,Cannady, J. Patrick,Leslie, Kenneth A.
, p. 6014 - 6019 (1980)
In this article the equilibrium constant and enthalpy for formation of the dioxygen adduct of the bis(salicylideniminato-3-propyl)methylaminocobalt(II) complex (CoSMDPT) are reported in methylene chloride solution (-9.8 kcal mol-1).When small amounts of 2,2,2-trifluoroethanol (TFE) are added, extra stabilization of the dioxygen adduct is found.The measured enthalpy for adduct formation increases to -11.8 kcal mol-1.Infrared frequency shift studies of the O-H stretching vibration indicate that TFE undergoes a hydrogen-bonding interaction with the coordinated dioxygen.An enthalpy-frequency shift, ΔνOH, relation provides an estimate of a 6.6 kcal mol-1 hydrogen bond strength.This is one of the few instances in which a clear-cut reaction of the coordinated dioxygen is shown.This interaction suggests an explanation for the high oxygen affinities of such systems as cobalt myoglobin and CoTpivPP*MeIm compared to cobalt(II) protoporphyrin IX dimethyl ester.
STERIC AND ELECTRONIC EFFECTS OF LIGAND VARIATION ON COBALT DIOXYGEN CATALYSTS
Corden, Barry B.,Drago, Russel S.,Perito, Richard P.
, p. 2903 - 2907 (2007/10/02)
We report herein the observation that electronic and steric factors of cobalt dioxygen complexes with systematically derivatized pentadentate Schiff-base ligands affects their ability to catalyze the oxidation of sustituted phenols and alter the rate of catalyst decomposition.The electronic and steric factors can be separated sufficiently to indicate that the activity of the cobalt dioxygen catalyst roughly parallels the trends in basicity of the bound O2 suggested by EPR cobalt hyperfine coupling constants of the adducts and predicted from the electronic effects of substituents.
Regioselective Formation of Peroxyquinolatocobalt(III) Complexes in the Oxygenation of 2,6-DI-t-butylphenols Schiff-base Complexes
Nishinaga, Akira,Tomita, Haruo,Nishizawa, Kanji,Matsuura, Teruo,Ooi, Shunichiro,Hirotsu, Ken
, p. 1504 - 1514 (2007/10/02)
The oxygenation of 2,6-di-t-butylphenols with five-co-ordinated cobalt(II) Schiff-base complexes in aprotic solvents, such as CH2Cl2, thf, and dmf (thf = tetrahydrofuran, dmf = dimethylformamide), has been found to result in regioselective formation of peroxyquinolatocobalt(III) complexes.The regioselectivity depends on the nature of the substituent at the 4-position of the phenol used: 4-alkyl-2,6-di-t-butylphenols(1) afford peroxy-p-quinolatocobalt(III) complexes, whereas peroxy-o-quinolato-complexes are formed from 4-aryl-2,6-di-t-butyl-phenols (4).The initiation of the oxygenation is hydrogen abstraction by superoxocobalt(III) species from the phenols to give the corresponding phenoxy-radicals (10).Rapid reduction of (10) with cobalt(II) species follows giving rise to a phenolatocobalt(III) complex intermediate, within which dioxygen is incorporated.The regioselectivity of the oxygenation is attributable to the formation of the phenolatocobalt(III) complex intermediate.Crystals of the peroxy-p-quinolatocobalt(III) complex (2a) are orthorombic, space group P212121, with a = 33.749(11), b = 11.844(5), c = 9.329(4) Angstroem, and Z = 4.The crystal structure has been refined from 3 018 diffractometer data to R = 0.067.
