Complex ammonia

In recent years a great amount of information about the structure of inorganic complexes has been gathered by the methods of x-ray diffraction, measurement of magnetic susceptibility, magnetic resonance spectroscopy, Mossbauer spectroscopy, and other techniques. This information about the structure of complexes has been correlated with their chemical properties in such a way as to bring reasonable order into this field of chemistry. 

A solution of a cupric salt is blue in color. This blue color is due to the absorption of yellow and red light, and consequent preferential transmission of blue light. The molecular species that absorbs the light is the 

The cis and irons isomers of the cobaltic telrammine dichloride ion, Co(NH3)4Cl2 . In the cis form the two chlorines occupy adjacent corners of (he coordination octahedron about the cobalt atom, and in the irons form the two chlorine atoms occupy opposite corners. 

When a few drops of sodium hydroxide solution are added to a cupric solution a blue precipitate is formed. This is cupric hydroxide, Cu(OH)2, which precipitates when the ion concentration product [Cu ] [OH ] reaches the value corresponding to a saturated solution of the hydroxide. (Here the symbol Cu + is used, as is conventional, for the ion species Cu(H20)4. ) Addition of more sodium hydroxide solution leads to no further change, other than the formation of more precipitate. 

If ammonium hydroxide is added in place of sodium hydroxide the same precipitate of Cu(OH)2 is formed. On addition of more ammonium hydroxide, however, the precipitate dissolves, giving a clear solution with a deeper and more intense blue color than the original cupric solution.  

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Qualitative. The classic method for the quaUtative determination of silver ia solution is precipitation as silver chloride with dilute nitric acid and chloride ion. The silver chloride can be differentiated from lead or mercurous chlorides, which also may precipitate, by the fact that lead chloride is soluble ia hot water but not ia ammonium hydroxide, whereas mercurous chloride turns black ia ammonium hydroxide. Silver chloride dissolves ia ammonium hydroxide because of the formation of soluble silver—ammonia complexes. A number of selective spot tests (24) iaclude reactions with /)-dimethy1amino-henz1idenerhodanine, ceric ammonium nitrate, or bromopyrogaHol red [16574-43-9]. Silver is detected by x-ray fluorescence and arc-emission spectrometry. Two sensitive arc-emission lines for silver occur at 328.1 and 338.3 nm. 

In the absence of ammonia and the concentration of polyamines being > 20 p.M the production of sediments take place. Ethylene diamine reacts with Hg(II) in the form of diimide -HNRNH- to form the insoluble complex IHgHNRNHHgl. In the presence of ammonia the production of sediments having complex composition is also possible. Given concentration of K Hgl 1-2 mM, NaOH 60-120 mM and compai able amounts of ammonia and ethylene diamine the products of reactions ai e only the soluble green-coloured complexes, bearing ammonia in the form of nitride and ethylene diamine in the form of diimide. Those complexes ai e polymers, with their absorption spectmms being different from those of the similar polymeric ammonia complexes. 

Metal salts in alkaline solution Cuprammonium complex Nickel and cobalt ammonia complex Cyanides (q.v.) Copper pyrophosphates Plumbites Zincates... 

In a linear complex, the coordination number is 2, corresponding to one group on each side of the central atom. The silver-ammonia complex, which generally forms when a very slightly soluble silver salt such as silver chloride dissolves in aqueous ammonia, is an example, as shown in Figure 22-6. Another example of a linear com-... 

The Raman spectroscopic work of Ja-covitz [31], Cornilsen et al. [32, 33], and Audemer et al. [34] is the most direct spectroscopic evidence that the discharge product in battery electrodes, operating of the pi ji cycle, is different from well-crystallized / -Ni(OH)2. The O-H stretching modes and the lattice modes in the Raman spectra are different from those found for well-crystallized Ni(OH)2, prepared by recrystallization from the ammonia complex, and are more similar to those... 

If copper is present in the boiler FW (normally as the cupric ammonia complex ion), boiler surfaces are directly attacked by electrolytic reduction. In strongly alkaline conditions the ferrous ion is present as ferrous hydroxide [Fe(OH)2] ... 

Cupric ammonia complex ion corrosion Resulting plated copper acts as cathode to surrounding anodic boiler steel, inducing corrosion. 

Animation Figure 15.4 Formation of a copper-ammonia complex... 

If the bonds are ionic or ion-dipole bonds, the magnetic moments are those of the isolated central ions, given in the first column of moments in Table III. If the complex involves electron-pair bonds formed from sp alone, such as four tetrahedral sp3 bonds, the magnetic moments are the same, for the five d eigenfunctions are still available for the remaining electrons. The hydrazine and ammonia complexes mentioned above come in this class. 

Metal cations in aqueous solution often form chemical bonds to anions or neutral molecules that have lone pairs of electrons. A silver cation, for example, can associate with two ammonia molecules to form a silver-ammonia complex ... 

Notice that square brackets are used in a new way for the silver-ammonia complex in the chemical reaction. Chemists use square brackets to identify a complex ion such as [Ag (NH3)2, because the species involved in... 

The stoichiometiy of a metal complex is described by its chemical formula. For example, each cation of the silver-ammonia complex contains one Ag cation bound to two neutral NH3 ligands and carries a net charge of -i-l, as shown in Figure 18-11. The formula of a complex ion is enclosed in square brackets, as in [ Ag (NH3)2. The... 

Because the two equilibrium constant expressions have similar magnitudes, a solution of the silver-ammonia complex generally has a significant concentration of each of the species that participate in the equilibria. The details of such calculations are beyond the scope of general chemistry. When the solution contains a large excess of ligand, however, each step in the complexation process proceeds nearly to completion. Under these conditions we can apply the standard seven-step approach to a single expression that describes the formation reaction of the complete complex. 

Chelating ligands bind much more tightly to their metal cations than do ligands that possess only one donor atom. A good example is the ethylenediamine complex with. The ethylenediamine complex is much more stable than the analogous ammonia complex ... 

Although 6 Is most prevalent, a coordination number of 4 Is also common, and several important complexes have a coordination number of 2. In addition, a few complexes display coordination numbers of 3, 5, and 7. Examples of coordination number 2 include the silver-ammonia complex and the gold-cyanide complex, both described in Chapter 18. To minimize ligand-ligand repulsions, a complex with a coordination number of 2 is invariably linear, as Figure 20-6 shows. 

Some molecular solvents (such as ammonia, aliphatic amines, hexamethyl-phosphortriamide) dissolve alkali metals solutions with molalities of more than 10 mol kg-1 are obtained. Ammonia complexes M(NH3)6 analogous... 

MNH3 is added with Cu2+(a ) + 4NH3(a ) Y [Cu(NH3)4]2+(t/<7) What happens depends on the relative values of Kc for the formation of Cu(OH)2(.v) and the Kc for the formation of [Cu(NH3)4]2+Uw/). If one value of Kc is much larger than the other, then that equilibrium will prevail. Since in this problem, we don t know what the Kc values are, we can simply guess that the formation of the copper-ammonia complex would decrease the concentration of Cu2+ in solution and that some or all of the Cu(OH)2(s) might dissolve. 

NH3 and Zn2+ have reacted together to give a very stable zinc-ammonia complex ... 

Some doubt is thrown on B strain as the sole explanation of the branching effect by the observation that the tri-te -butylboron-ammonia complex is actually less dissociated than the trimethylboron-ammonia complex.227 Since the products of the ionization of these highly branched compounds contain large amounts of rearranged material, another effect may be operating. As will be discussed in the next section, many ionization reactions produce directly an ion of structure different from that of the covalent parent compound. The transition state presumably resembles the new ion or a non-classical... 

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