O-phenanthroline Complexes

This experiment describes the use of FIA for determining the stoichiometry of the Fe +-o-phenanthroline complex using the method of continuous variations and the mole-ratio method. Directions are also provided for determining the stoichiometry of the oxidation of ascorbic acid by dichromate and for determining the rate constant for the reaction at different pH levels and different concentration ratios of the reactants. 

The oxidation of butanone-2, catalyzed by complexes of pyridine with cupric salts, appeared to be similar in its main features [191]. Butanone-2 catalytically oxidizes to acetic acid and acetaldehyde. The reaction proceeds through the enolization of ketone. Pyridine catalyzes the enolization of ketone. Enole is oxidized by complexes of Cu(II) with pyridine. The complexes Cu(II).Py with n = 2,3 are the most reactive. Similar results were provided by the study of butanone-2 catalytic oxidation with o-phenanthroline complexes, where Fe(III) and Mn(II) were used as catalysts [192-194],... 

The oxidation of alcohols in a basic solution catalyzed by Cu(II) o-phenanthroline complexes has been recently studied by Sakharov and Skibida [305-309], The copper-phe-nanthroline complex is stable in a basic solution and appears to be a very efficient catalyst for the oxidation of alcohols to carbonyl compounds. The reaction rate increases with an increase in the partial pressure of dioxygen. The solvent dramatically influences the reaction rate (conditions 348 K, [MeOH] = 20%vol, [Cu—(o—phm)] = 0.01 mol L-1). 

Using one of your standards and the Spectronic 20, or other single-beam visible spectrophotometer, obtain an absorption (or transmittance) spectrum of the Fe-o-phenanthroline complex ion (instructor will demonstrate use of instrument). Determine the wavelength of maximum absorbance from the spectrum and use this wavelength to obtain absorbance readings of all the solutions. (Use the blank for the 100% transmittance setting.)... 

A trial was made to take a look at the valence of iron in adrenodoxin (29) using 3 moles of p-chloromercuribenzoate (PCMB) per gram atom of iron (less than saturated level of PCMB), all of the iron could be extracted by 5% trichloroacetic acid solution as ferric iron, which produces a ferrous-o-phenanthroline complex only by the addition of ascorbate as reductant. In the absence of the mercurial, some 50% or more of the iron atoms in the protein can be removed in the ferrous state. This result indicates that the acid extraction causes intramolecular reduction of the protein-bound iron. As shown in Fig. 10, 5.7 M urea as a protein denaturant can slowly bleach the visible absorption under aerobic conditions. About 10% of the residual absorption remains at 414 mp after the reaction is completed. In the presence of both urea and o-phenanthroline, all of the iron present in adrenodoxin reacts with o-phenanthroline to produce the ferrous complex under aerobic conditions. Similar experiments under anaerobic conditions reveal that the... 

Caution. Tris(o-phenanthroline) complexes should be handled with care because of potential high toxicity. 

Terpyridine was reported 65) to give square complexes with zinc(II), however, the complex has been foimd to be a trigonal bipyramid with the anions occupying two positions 21). Neither 2,2 -dipyridine nor o-phenanthroline complexes has been shown to form square planar structures with any of the first row transition metals (5, 70), although in the presence of weakly coordinating solvents and anions this geometry may be achieved. 

Although the resolution into their enantiomeric forms of octahedral metal complexes bearing bidentate ligands was accomplished at an early stage,19 the application of such materials for the preparation even of dinuclear complexes was greatly delayed.20 Only recently has the preparation of a particular stereoisomer of a diruthenium complex been accomplished by the resolution of the bis-o-phenanthroline complex (9). The subsequent use of the optically active material in a stereoselective reaction with 2,5-bis(2-pyridyl)pyrazine (10) yielded the dinuclear com-... 

Unlike the native protein, urea treatment resulted in a measurable reactivity of the iron with o-phenanthroline, the ferrous-o-phenanthroline complex remaining attached to the protein (244). The metal is so tightly bound that attempts to remove it without complete denaturation of the protein failed. Release of H2S was promoted in 8 M urea even at pH... 

The structure of the enz5nne-o-phenanthroline binary complex shows that o-phenanthroline occupies this cleft while coordinated to the active site zinc ion. Note that the LADH zinc ion o-phenanthroline complex is pentacoordinate. 

Some of the cyclobutadiene complexes [e.g., (XIII) and (XXVIII)] appear to be inert to the action of donor ligands such as phosphines, pyridine, etc. However, a number form adducts. These have not been fully described, but triphenylphosphine adducts of tetramethylcyclobutadienenickel chloride (XIV) (28) and tetraphenylcyclobutadienenickel bromide (XXXIII) (41) and an o-phenanthroline complex (29) of the former have been reported. Other reactions with donor molecules in which the cyclobutadiene-metal bond remains intact are mentioned in Section VI, G. 

The oxidation of n-propanol and benzylic alcohol to the corresponding aldehydes is catalyzed by copper-o-phenanthroline complexes [36], Kinetic studies have been performed at 30-70 C in aqueous alkaline solutions (n-propanol) or in DMF. A concerted 2-electron process was assumed to take place (Equation 11). 

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