Cobalt complexes ethylenediamine complex

R.F. Howe and J.H. Lunsford, Oxygen Adducts of Cobalt(n)-ethylenediamine Complexes in X- and Y-type Zeolites. J. Phys. Chem., 1975, 79, 1836-1842. 

In addition to molybdic acid, there have been reports of several other catalytic systems that cause mechanistically relative transformations of aldoses involving a 1,2-shift of their carbon skeleton. They include the nickel(II)-ethylenediamine [43] and cobalt(II)-ethylenediamine complexes [44] as well as the calciiun(II), strontium(II),lanthanum(III) and neodymium(III) cations in both aqueous and alcoholic alkaline solutions [45,46]. Unlike the BiTik reaction, all these transformations exploit rather equimolar amounts of the catalysts so that they result in thermodynamic equilibria of the catalytic complexes with the epimeric aldoses. Moreover, due to steric restrictions, the aforementioned alkaline earth and rare earth cations, which form mononuclear tetradentate complexes with aldoses. 

Dumond F., Marceau E., and Che M. 2007. A study of cobalt speciation in Co/Al203 catalysts prepared from solutions of cobalt-ethylenediamine complexes. J. Phys. Chem. C 111 4780-89. 

If hydrolysis plays a role in the sorption process, the slight differences for the Co/Mn ratio at the higher pH could be related to the relatively lower rates for hydrolysis of the cobalt ethylenediamine complex at low pH (27). 

The amount of ammonia volatilized was determined from the amount of standard sulfuric acid consumed in the traps. Ethylenediamine was determined by the salicylaldehyde method (14). The sample for cobalt(II) determination was made slightly acidic with hydrochloric acid immediately upon removal of the sample from the reaction flask, in order to prevent further oxidation of the cobalt (18). The carbon was removed by filtration, and the cobalt (II) concentration was determined spectrophotometrically as the cobalt-ammonium thiocyanate complex, (NH4)2Co(NCS)4 (28). 

Although no direct evidence was found in the cobalt-N-hydroxyethylethyl-enediamine reaction that an oxygen-cobalt addition complex was formed, it seems reasonable to postulate that such an intermediate is present in the reaction. An oxygen-cobalt complex intermediate appears to afford the most logical method of explaining the evidence that the oxidation of cobalt (II) to cobalt (III) occurs in conjunction with the oxidative cleavage of the carbon-carbon bond of the hydroxyethyl group and the formation of ethylenediamine. 

Isomer Ratios for Cobalt(III) Ethylenediamine and (—)-Propylenediamine Complexes (13)... 

The hydrolysis of adenosine 3. 5 -cyclic monophosphate (cAMP) by the cobalt complexes (215) was considered here earlier,187 as was the Ce(IV)-catalysed hydrolysis of phospho monoesters in nucleotides.189 A review (ca 100 references) on current data on the mechanism of cleavage-transesterification of RNA has appeared.258 In this review special attention was focused on the two crucial steps in the hydrolysis of RNA, i.e. cleavage-transesterification and hydrolysis of the cyclic phosphodiester (Scheme 14). The catalysis of various amines for the hydrolysis of RNA has been looked at and ethylenediamine and propane-1,3-diamine are highly active under physiological conditions because they exist as the catalytically active monocation forms.259... 

FIG. 22. Preparation of a cyanocobalt(II)-chiral diamine catalyst solution. The cobalt species in solution may resemble the ethylenediamine complex (VI). 

It was her thesis work with Alfred Werner34 that was to enter her in the annals of the history of chemistry. Among the compounds she made was cis-bis(ethylenediamine)dinitro-cobalt(III) bromide. This was the very first synthesis of a chiral octahedral cobalt complex, though at the time the significance of her synthesis was overlooked.31(a) Werner was so impressed with her work that, for her last year, he took her on as his personal assistant, the first women to be chosen for this prestigious post.35 More important for the impoverished Humphrey, she at last had some income in very expensive Switzerland. 

Fig. 23.1 Structure of ICo(en)3l3+. It is a six-co-ordinate octahedral complex of ethylenediamine (en) with cobalt (III). The complex has three five-membered rings.

Since the reviews have stressed the numerous stereochemical studies which have been conducted on the octahedral bis(ethylenediamine) complexes of cobalt(III), those results will be reiterated only briefly. 

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