Ammonia metal complexes

Of the other atomic complexes, such as the alkali metal and alkaline earth metal-ammonia complexes, Li(NH3)4,... 

Complex ions are any ions that are built up by the union of simpler ions, or of an ion and one or more neutral molecules. They are usually formed around metallic ions. They may be held together entirely by coordinate hnks, as in Cu(NH3)4 and the other metal-ammonia complexes, or they may be bound by a combination of coordinate links and normal covalent links, as in Hgl4 or Fe(CN)6 . They may even be held together by purely ionic or electrostatic forces, as is the case in FeFe this complex is shown by its large magnetic moment to contain a free ferric ion, yet it is extremely stable, since the small size of the fluoride ion allows for close approach and a strong electrostatic force between Fe" and F . 

See the general references in the Introduction, and more-specialized books [1-19], Some articles in journals include the prediction of formation constants of metal-ammonia complexes in water using density-functional theory [20] an introduction to a thematic issue on NO chemistry [21] the oxidation of diazane, N2H4, in water [22] dinitrogen complexes [23] open-chain polyphosphorus hydrides [24] per-oxynitrites [25] nitrogen fixation [26 and 27] NO on d-block metals [28] mechanisms of nitrogen-compound reactions [29] N2 fixation [30] and common Bi [31]. 

The product of this reaction is called a metal-ligand complex. In writing the equation for this reaction, we have shown ammonia as NH3 to emphasize the pair of electrons it donates to Cd +. In subsequent reactions we will omit this notation. 

Inorganic heavy metals are usually removed from aqueous waste streams by chemical precipitation in various forms (carbonates, hydroxides, sulfide) at different pH values. The solubiUty curves for various metal hydroxides, when they are present alone, are shown in Figure 7. The presence of other metals and complexing agents (ammonia, citric acid, EDTA, etc) strongly affects these solubiUty curves and requires careful evaluation to determine the residual concentration values after treatment (see Table 9) (38,39). 

The ahphatic alkyleneamines are strong bases exhibiting behavior typical of simple aUphatic amines. Additionally, dependent on the location of the primary or secondary amino groups iu the alkyleneamines, ring formation with various reactants can occur. This same feature allows for metal ion complexation or chelation (1). The alkyleneamines are somewhat weaker bases than ahphatic amines and much stronger bases than ammonia as the piC values iadicate (Table 2). 

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

By a suitable choice of conditions (metal hydrides or metal/ammonia) ketones at the 1-, 2-, 4-, 6-, 7-, 11-, 12- and 20-positions in 5a-H steroids can be reduced to give each of the possible epimeric alcohols in reasonable yield. Hov/ever, the 3- and 17-ketones are normally reduced to give predominantly their -(equatorial) alcohols. Use of an iridium complex as catalyst leads to a high yield of 3a-alcohol, but the 17a-ol still remains elusive by direct reduction. 

Scheme 12 Synthesis of metal polysulfido complexes using supercritical ammonia as a solvent...

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 ... 

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... 

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 a wide variety of metals were claimed as active catalysts for formaldehyde hydrophosphination, platinum salts were preferred. Similarly, Group 10 metal salts were used to catalyze acrylonitrile hydrophosphination. Russian workers showed that Ni(II) or Co(II) salts in the presence of ammonia or amines would also catalyze the addition of phosphine to formaldehyde [6]. More recently, academic and industrial interest in these reactions was sparked by a series of papers by Pringle, who investigated late metal phosphine complexes as hydrophosphination catalysts. These and related studies are arranged below by substrate. 

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... 

Armannsson [659] has described a procedure involving dithizone extraction and flame atomic absorption spectrometry for the determination of cadmium, zinc, lead, copper, nickel, cobalt, and silver in seawater. In this procedure 500 ml of seawater taken in a plastic container is exposed to a 1000 W mercury arc lamp for 5-15 h to break down metal organic complexes. The solution is adjusted to pH 8, and 10 ml of 0.2% dithizone in chloroform added. The 10 ml of chloroform is run off and after adjustment to pH 9.5 the aqueous phase is extracted with a further 10 ml of dithizone. The combined extracts are washed with 50 ml of dilute ammonia. To the organic phases is added 50 ml of 0.2 M-hydrochloric acid. The phases are separated and the aqueous portion washed with 5 ml of chloroform. The aqueous portion is evaporated to dryness and the residue dissolved in 5 ml of 2 M hydrochloric acid (solution A). Perchloric acid (3 ml) is added to the organic portion, evaporated to dryness, and a further 2 ml of 60% perchloric acid added to ensure that all organic matter has been... 

As a simple proof that a complex-like structure forms on the surface of metals immersed in a mixture of nitrogen and hydrogen gases, try immersing a piece of red-hot bronze in an atmosphere of ammonia. The surface of the metal soon forms a tough, impervious layer of bronze-ammonia complex, which imparts a dark-brown colour to the metal. The brown complex reacts readily with moisture if the metal is iron and is impermanent, but the complex on bronze persists, thereby allowing the colour to remain. 

The fact that complex 38 does not react further - that is, it does not oxidatively add the N—H bond - is due to the comparatively low electron density present on the Ir center. However, in the presence of more electron-rich phosphines an adduct similar to 38 may be observed in situ by NMR (see Section 6.5.3 see also below), but then readily activates N—H or C—H bonds. Amine coordination to an electron-rich Ir(I) center further augments its electron density and thus its propensity to oxidative addition reactions. Not only accessible N—H bonds are therefore readily activated but also C—H bonds [32] (cf. cyclo-metallations in Equation 6.14 and Scheme 6.10 below). This latter activation is a possible side reaction and mode of catalyst deactivation in OHA reactions that follow the CMM mechanism. Phosphine-free cationic Ir(I)-amine complexes were also shown to be quite reactive towards C—H bonds [30aj. The stable Ir-ammonia complex 39, which was isolated and structurally characterized by Hartwig and coworkers (Figure 6.7) [33], is accessible either by thermally induced reductive elimination of the corresponding Ir(III)-amido-hydrido precursor or by an acid-base reaction between the 14-electron Ir(I) intermediate 53 and ammonia (see Scheme 6.9). 

The reaction of aqneons green Np, or its bine ammonia complex, with colorless dimethylglyoxime (DMG) to form a vibrantly red precipitate of a 1 2 metaLDMG complex demonstrates an example of precise stereochemistry and oxime deprotonation in what is perhaps the archetypal analytical metal dioxime reaction (equation 1). This transformation certainly intrigued both authors early in their education. It is interesting to note that DMG is an excellent example of highly specific reagent because under the same reaction conditions only yellow palladium chelate is also precipitated. 

Forms a number of coordination compounds (ammonia complex) with several metals adds to AgCl forming soluble complex [Ag(NH3)2]Cl forms tetraamine complex [Cu(NH3)4]S04 with CUSO4 and forms many hexaamine complexes with cobalt, chromium, palladium, platinum and other metals. 

The effects of other contaminants in the feed stream was tested using ammonia and ethylene-diaminetetraacetic acid (EDTA). While ammonia had little effect on the effectiveness, EDTA affected efficiency significantly. When the metals were complexed with EDTA, they broke through almost immediately, making the capacity of the media to remove metals not significant... 

They based this modification on the known adsorbance of OH on glass and on the common occurrence of transition metal mixed water-ammonia complexes with coordination number of 4. Parallel stractural studies of the deposited CdS showed textured growth, supporting a mechanism whereby alternate Cd and S species were involved, in an ion-by-ion process. Such a growth suggests adsorption of a molecular hydroxy-ammine species rather than a cluster. In fact, the mechanism of Ortega-Borges and Lincot also does not differentiate between a hydroxide cluster and molecule. 

ZnO films for use as buffer layers in photovoltaic cells (see Chap. 9) have been chemically deposited from aqueous solutions of ZnS04 and ammonia [57]. The solution was heated to 65°C, and adherent, compact Zn(OH)2 + ZnO films were formed after one hour. Low-temperature annealing converted the hydroxide to oxide. The solution composition will be important in this deposition. On one hand, increased ammonia concentration will increase the pH and therefore the homogeneous Zn(OH)2 precipitation in solution. However, further increase in ammonia concentration will redissolve the hydroxide as the ammine complex. There will clearly be an optimum ammonia (and zinc) concentration where Zn(OH)2 does form, but slowly enough to prevent massive homogeneous precipitation. The use of ammonia in (hydr)oxide deposition derives, in part at least, from its gradual loss by evaporation if the system is not closed [58], Any open solution of an ammonia-complexed metal ion (which forms an insoluble hydroxide or hydrated oxide) should eventually precipitate the (hydr)oxide for this reason alone. 

Using ammonia-complexed metal iodides and thiourea at pH 10, films were formed whose properties depended on the temperature-time regime of the depo-... 

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