Ethylenediamine cobalt compounds

In the following, a series of preparations of dianionobis(ethyl-enediamine)cobalt(III) compounds, all starting with (carbonato)-bis(ethylenediamine)cobalt(III) chloride are given. (Carbonato )bis-(ethylenediamine)cobalt(III) chloride has been prepared with a high yield (80%) by a new method based upon the use of cobalt(II) chloride and the equivalent amount of (2-aminoethyl)-carbamic acid. The carbonato compound is easily converted into a number of dianionobis(ethylenediamine)cobalt(III) compounds with high yields. In some of the following procedures it was possible to use the carbon dioxide-ethylenediamine reaction mixture directly. 

Tris[tetrammine-M-dihydroxo-cobalt(III)] cobalt(III) sulfate is analogous to the tris(ethylenediamine) compounds, with each ethylenediamine molecule replaced by the biden-... 

The very different basicities of water and of ammonia lead to different reactivity patterns for iSNlcb base hydrolyses of cobalt(iii) compounds. The latest contribution in this area has been a study of base hydrolysis of a series of complexes [Co(NH3)6(RNHa)] + in liquid ethylenediamine. The basicity or solvating power of the solvent determines the form of the rate law for substitutions at copper(ii)-Schiff base complexes. The term corresponding to solvolysis is, of course, only significant for solvents with an affinity for copper(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. ... 

In the complex [Co(NH3)6]Cl3, the cation is [Co(NH3)6]3+, and it is named first. The coordinated ammonia molecules are named as ammine, with the number of them being indicated by the prefix hexa. Therefore, the name for the compound is hexaamminecobalt(III) chloride. There are no spaces in the name of the cation. [Co(NH3)5C1]C12 has five NH3 molecules and one CN coordinated to Co3+. Following the rules just listed leads to the name pentaamminechlorocobalt(III) chloride. Potassium hexacyanoferrate(III) is K3[Fe(CN)6j. Reinecke s salt, NH4[Cr(NCS)4(NH3)2], would be named as ammonium diamminetetrathiocyanatochro mate (III). In Magnus s green salt, [Pt(NH3)4][PtCl4], both cation and anion are complexes. The name of the complex is tetraammineplatinum(II) tetrachloroplatinate(II). The compound [Co(en)3](N03)3 is named as tris(ethylenediamine)cobalt(III) nitrate. 

The importance of metal coordination compounds in biological systems has led to the study of polydentate Schilf base complexes of cobalt(II), nickel(II), and copper(II) (204, 205). Dimers have been observed in the spectra of complexes of both tri- and tetradentate ligands [e.g., salicylaldehydeand A,A-bis(salicylidene)ethylenediamine]. The parent ions form the base peaks, and the spectra are characterized... 

A series of compounds is know ll belonging to the diaquo-series, w here ethylenediamine replaces ammonia, the diaquo-diethylenedi-amino-cobaltic salts, [Co en2(H20)2]R3. These exist in isomeric forms, intensely red a. s-diaquo-salts and browmish-red bvms-diaquo-salts. The irans-series may be produced from the eis-series by treating it with some potassium hydroxide and nibbing the brms-hydroxo-aquo-salt, [Co en2H20(0H)]R2, produced with concentrated mineral acid. 

L [(OH),Co en Jg cobaltous chloride and ethylenediamine on oxidation with air and subsequent treatment with sodium chloride to precipitate the compound. The crude salt contains a little triethylenediamino-cobaltic chloride, which is removed from the sparingly soluble tetraethylenediamino-diaquo-tetrol-chloride by washing with water. It is a bright red micro-crystalline powder. 

The question might be asked Are there similar mechanisms for changing the configuration of molecules without breaking bonds in molecules with coordination numbers other than 3 and 5 The answer is yes. One of the most important series of inorganic compounds consists of six-coordinate chelate compounds exemplified by the tris(ethylenediamine)cobalt(lIl) ion. Because of the presence of the three chelate rings, the ion is chiral and racemization can take place by a mechanism that is closely related to atomic inversion or Berry pseudorotaiion (the mechanism for six-coordination is termed the Bailar twist see Chapter 13k... 

Several interesting compounds can be simply prepared by metathesis of equivalent amounts of a soluble di-tris-(ethylenediamine) cobalt (III),... 

The examples of metal-chiral structures are mainly cationic mixed-ligand cobalt(III) complexes of ethylenediamine and its monodimethylphosphine analogue [Co(H2NCH2CH2NH2)3(H2NCH2CH2PMe3)3 J3+. Their synthesis, separation to enantiomers, and establishment of absolute configuration have been carried out for these compounds [276]. The binuclear cobalt(III) complexes 924 possess similar optical properties [277] ... 

Classical methods for the synthesis of frans-dinitro-bis(ethylenediamine)cobalt(III) nitrate involve conversion of the cis isomer by heat1 or action of sodium nitrite on frans-chloronitrobis(othylenediamine)cobalt(III) nitrate.2 These methods involve isolation of intermediate coordination compounds and consequently are subject to low yields, based upon original cobalt(II) salt. The following procedure for the preparation of the trans compound gives an 84% yield it depends upon oxidation of cobalt(II) to cobalt(III) in the presence of sodium nitrite, ethylene-diamine, and nitric acid. 

Werner1,3 prepared as-dinitrobis(ethylenediamine)co-balt(III) nitrate by heating ethylenediamine with potassium hexanitrocobaltate(III) to give the dinitrobis(ethylenedia-mine)cobalt(III) nitrite, followed by conversion to the nitrate with nitric acid. The procedure given here for the cis compound utilizes this method. 

The isomeric dinitrohis(ethylenediamine)cobalt(III) nitrates are relatively insoluble, 1.20 g. of the cis compound... 

Fe2(CO)9, and Fe3(CO)12, respectively. Similar disproportionations occurred with Ni(CO)4 and Co2(CO)8 which gave anionic species such as [Ni2(CO)6]2, [Ni3(CO)8]2, [Co(CO)4] , etc., upon treatment with ammonia or other amines. In contrast to the carbonyls of iron, nickel and cobalt, those of chromium, molybdenum and tungsten reacted with pyridine and 1,2-ethylenediamine to afford substitution products of the general composition M(CO)6 (py) (n = 1, 2, and 3) and M(CO)4(en) with the metal remaining in the oxidation state zero [25], Mainly as the result of this work, Hieber became convinced that the metal carbonyls should be regarded as true coordination compounds, and the coordinated CO should not be considered a radical but a monodentate ligand like NH3, pyridine, etc. He held this view despite the criticism by several of his contemporaries [3, 19] and was very pleased to see that in most textbooks published after 1940 this view had been accepted. 

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. 

Chloropentaamminecobalt(III) chloride forms red-violet rhomb-shaped crystals which decompose on heating above 150° with the stepwise loss of ammonia. The solubility of the salt in water at 25° is 0.4 g./lOO ml. The compound readily aquates in hot water, forming the aquopentaammine chloride. Chloropentaamminecobalt(III) chloride reacts with hot aqueous ethylenediamine or dZ-propylenediamine to form tris (ethylenediamine) cobalt (III) chloride or the corresponding propylenediamine compound, with liberation of ammonia. Concentrated sulfuric acid at room temperature produces a complex hydrogen sulfate of the chloro-pentaamminecobalt(III) ion. Aqueous mercury(II) chloride forms a characteristic precipitate of a double salt, [Co(NH3)6Cl]Cl2-3HgCl2, suitable for microchemical identification. Complete physical and chemical data may be found in Gmelin s handbook. ... 

The first successful resolution of coordination compounds was reported by Werner in 1911 and involved two series of complexes, the cw-chloroammine-bis(ethylenediamine)cobalt(III) series (with V. L. King) and the m-bromo-amminebis(ethylenediamine)cobalt(III) series (with E. Scholze). Of the two, the bromoammine series is easier to resolve because of the greater difference in solubility between the diastereoisomers that are formed with the resolving agent, silver ( + )-octahedral configuration first postulated by Werner for cobalt(III) in 1893. 

---