Nitrogen ammine complexes

Coordination Compounds. A large number of indium complexes with nitrogen ligands have been isolated, particularly where Ir is in the +3 oxidation state. Examples of ammine complexes include pr(NH3)3] " [24669-15-6], prCl(NH3)] " [29589-09-1], and / j -pr(03SCF3)2(en)2]" [90065-94-4], Compounds of A/-heterocychc ligands include trans- [xCX py)][ [24952-67-8], Pr(bipy)3] " [16788-86-6], and an unusual C-metalated bipyridine complex, Pr(bipy)2(C, N-bipy)] [87137-18-6]. Isolation of this latter complex produced some confusion regarding the chemical and physical properties of Pr(bipy)3]3+ (167). 

Photoreduction of ammine complexes containing aliphatic amines instead of ammonia does not lead to production of molecular nitrogen instead, a variety of other ligand oxidation products are formed. Moeller and co-workers have studied three such systems in 3M HC1 solution 58 59 rather similar results have been obtained in more dilute acid solutions.55... 

To a coordination chemist there is little distinction between ammonia and an organic amine. Both have the all important nitrogen donor atom and thus have the potential to behave similarly. Regrettably, structural information for ammine complexes is not included in the Cambridge Crystallographic Data File,2 as simple salts lack the necessary carbon atom. 

Nitrogen Ligands Table 2 Typical Ammine Complexes 01... 

On the other hand, the reaction of several dithiolenes with bipyridyl and related ligands was shown47-49 to lead to dithiolato complexes of the type (32) and (33), in which the nitrogen-containing ligands have displaced one of the dithiolene ligands. The related bis-ammine complex (NH3)2Pd(mnt) was the first dithiolato complex to be isolated.16... 

Sargeson and his coworkers have developed an area of cobalt(III) coordination chemistry which has enabled the synthesis of complicated multidentate ligands directly around the metal. The basis for all of this chemistry is the high stability of cobalt(III) ammine complexes towards dissociation. Consequently, a coordinated ammonia molecule can be deprotonated with base to produce a coordinated amine anion (or amide anion) which functions as a powerful nucleophile. Such a species can attack carbonyl groups, either in intramolecular or intermolecular processes. Similar reactions can be performed by coordinated primary or secondary amines after deprotonation. The resulting imines coordinated to cobalt(III) show unusually high stability towards hydrolysis, but are reactive towards carbon nucleophiles. While the cobalt(III) ion produces some iminium character, it occupies the normal site of protonation and is attached to the nitrogen atom by a kinetically inert bond, and thus resists hydrolysis. 

This reaction (between Cd2+ and NH3) involves the formation of a coordinated covalent bond where the element nitrogen of NH3 shares its single unshared electron pair with Cd2+ (see Chapter 1). The number of water molecules that could be displaced from the cation s hydration sphere depends on the concentration of NH3 and the strength by which it associates with the metal ion. In these complex ions, otherwise known as metal-ammine complexes, the metal is called the central atom and the associated molecule or ion is called the ligand. 

Very little is known about the metabolism of metal complexes, though a number of ammine complexes of cobalt(III) were used as nitrogen sources for aspergillus niger nearly forty years ago (150), and much more recently, both tris(ethylenediamine)cobalt(III) ions (757) and amino acid complexes (152) of cobalt(III) have served as nitrogen sources for species of pseudomonas. Correlations through enzymic selectivity are therefore as yet not... 

Nitrogen Ligands. The affinity of Fem for amines is low. No simple ammine complex exists in aqueous solution addition of aqueous ammonia only precipitates the hydrous oxide. For the reaction... 

Even though metal ions such as Ru(II), Ru(III) and Pt(II) are usually fairly inert to substitution with the type of nitrogen ligands found on nucleic acids, the close juxtaposition of intrabase, intrastrand and interstrand sites may facilitate metal ion movement so as to modulate mutagenic or anticancer effects. l ro clear examples of this have now been studied with ruthenium ammine complexes which point out the effects of both pH and electrochemical environments on these linkage isomerization reactions. 

A second difference between the two is the behaviour when the catalysts are fired in air. Claus salt initially decomposes to rhodium metal but in the presence of air is converted to the oxide which sinters rapidly. Thus a worse dispersion of rhodium is observed when Claus salt is fired in air than when it is fired in nitrogen or hydrogen/nitrogen. In the case of rhodium chloride a superior overall rhodium dispersion is achieved and air firing is not so detrimental to dispersion as it is for the ammine complex. These observations can again be explained in terms of the decomposition chemistry of the precursor. Newkirk and McKee (ref. 51) have studied the decomposition of rhodium chloride, both unsupported and supported on alumina,... 

It is again most convenient to consider such compounds together. Ruthenium(ll) Ammines.13 There is an exceedingly wide range of ruthenium ammine complexes and they are of special interest because of the ready formation of nitrogen (N2) complexes. 

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