Cobalt amine complexes coordination compound

Attempts to isolate the complex which forms trans polymer have been made, but no pure compounds have yet been isolated. From cobalt chloride, solid or liquid products were obtained which have variable composition. (Co = 5.7-15%, A1 = 5.2-10.6%, Cl = 20.6-26.2%, N = 4.5%, and replaceable ethyl groups 1.2-16.9%). It seems probable that in certain of these products some of the amine cobalt chloride complex is present without coordinated AlEt2Cl. The corresponding products from cobalt octoate have all undergone decomposition to a greater or lesser extent during isolation, but by suitably protecting the catalyst with other donors such as ethers or nonpolymerizable dienes, it may be possible to isolate a stable product. 

Probably, the most widely studied coordination compounds are the ammine complexes of cobalt(III). Their stability, ease of preparation, and slow reactions makes them particularly amenable to kinetic study. 8ince work on these complexes has been done almost exclusively in water, the reactions of the complexes with the solvent water had to be considered first. In general, ammonia or amines coordinated to cobalt(ni) are observed to be replaced so slowly by water that only the replacement of ligands other than amines is usually considered. 

Co(in) complexes promote similar reactions. When four of the six octahedral positions are occupied by amine ligands and two cis positions are available for further reactions, it is possible to study not only the hydrolysis itself, but the steric preferences of the complexes. In general, these compounds catalyze the hydrolysis of N-terminal amino acids from peptides, and the amino acid that is removed remains as part of the complex. The reactions apparently proceed by coordination of the free amine to cobalt, followed either by coordination of the carbonyl to cobalt and subsequent reaction with OH or H2O from the solution (path A in Figure 12-15) or reaction of the carbonyl carbon with coordinated hydroxide (path B). As a result, the N-terminal amino acid is removed from the peptide and left as part of the cobalt complex in which the a-amino nitrogen and the carbonyl oxygen are bonded to the cobalt. Esters and amides are also hydrolyzed by the same mechanism, with the relative importance of the two pathways dependent on the specific compoimds used. 

Recent studies have shown that coordinated ammonia and amine ligands under basic conditions may effect nucleophilic attack at carbonyl centres in organic compounds, " These reactions occur due to formation of deprotonated amido species which can act as nucleophiles. For example, reaction of cobalt(III) and platinum(IV)ammines with ketones gives the corresponding Co and Pt imine complexes. A similar reaction between [Ru(NH3)6] and diones produces the corresponding Ru diimine (108). It has also been found that nitrilepentaammineruthenium(II)... 

D-Glucosamine and either ammonia, 1,2-ethylenediamine, or 1,10-phenanthroline have been shown to form complexes with Co (III) ions, and the cobalt (ethylenediamine. D-glucosamine) complex is formed from the a-pyranose anonoo of the sugar. Aldose oximes on catalytic hydrogenation afford bis(polyhydroxyalkyl)amines. These compounds and their N-carboxymetbyl derivatives react with borate ions to give maciocyclic diborate esters which can sequester Ca, Cu and Cd ions. The coordination of some divalent transition metal imis to 2-amino-2-deoxy-D-g(ycero-D-gu/o-heptonic acid in aqueous solution has beat studied. ... 

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