Zinc complexes ammonia

Co-ordination of the ligand to the zinc activates it towards nucleophilic attack by ammonia and the product is the zinc complex of a conjugated dianionic tetraaza macrocycle (Fig. 8-35). This ligand is of some interest in forming a very stable lithium complex, derivatives of which have found some application in photoaddressable devices. 

The preparation of the hexaammine complexes of ruthenium(II) and ruthenium (III) salts are sketchily described in the literature. The preparation of hexaammineruthenium(II) by the reduction of ruthenium trichloride with zinc in ammonia is described briefly by Lever and Powell.1 Allen and Senoff2 carry out the reduction using hydrazine hydrate. The hexaammineruthe-nium(III) cation is obtained by oxidation of the ruthenium(II) complex,1 and pentaamminechlororuthenium(III) dichloride is obtained by treating the former compound with hydrochloric acid.1,3 This compound may also be obtained by treating the pentaammine molecular nitrogen complex of ruthenium(II) with hydrochloric acid.2,4... 

The catalytic effect of several alcohols in the preparation of dichlorotetrakis(pyridine)rhodium(III) cation has long been known.1 In recent years, a variety of reducing agents, present in catalytic quantities, have been used in the preparation, of several rhodium(III) complexes.2 In the absence of catalysts, these reactions are often laborious, and/or incomplete, by comparison with the catalyzed reaction, for example, the preparation of pentaamminechlororhodium(III) chloride (Claus salt) by the method of Lebedinsky.3 Conversion of [Rh(NII3)[,CI]Cl2 to the pentaamminehydridorhodium(III) salt [Rh(NII3) I 1JW()4 by treatment with zinc and ammonia is rapid, and the reaction is relatively clean.4 The formation of hydrido species by tetrahydroborate treatment6 is not a satisfactory preparative procedure. 

In Appendix 4, we find that the logarithms of the stepwise formation constants for the four zinc complexes with ammonia are 2.21,2.29, 2.36, and 2.03. Thus,... 

In the presence of the ammonium cation, zinc hydroxide cannot precipitate either with alkaline hydroxides or with ammonia because of the formation of soluble ammine zinc complexes such as the tetraamminezinc(II) cation [Zn(NH3)4] ". However, Zn + can be precipitated from these complexes by alkaline sulfides ... 

The well-known synthesis of the dmit ligand (40) was first reported in 1975 from carbon disulphide and sodium in dimethylformamide (DMF) [63]. The dmit ligand can be separated of the sodium trithiocarbonate (39) obtained in the reaction by precipitating the zinc complex (41), formed in aqueous ammonia, with methanol (Scheme 1.11). This procedure was later improved [64] and the dmit ligand better protected by converting the tetraalkylammonium zinc complex (41) into the benzoyl derivative (42) by reaction with benzoyl chloride. The dmit dianion (40) can be regenerated from the benzoyl derivative by treating with sodium methoxide. Fmfher treatment with the metal salt (M = Ni, Pd, Pt, Fe, Au, Cu, Rh) affords the dmit complex [61]. 

The aquo-complex [ZnlHjOlg] and the tetrahedral [ZnCU] have already been mentioned. Numerous hydroxo-complexes, foi example [ZnfOH) ], [Zn(OH)4] have been described. Additior. of excess ammonia to an aqueous Zn(II) solution produces the tetraamminozinc cation [Zn(N 113)4]-. Hence zinc tends to form 4-coordinate, tetrahedral or (less commonly) 6-coordinate octahedral complexes. 

Ammonia NH3 Corrosion of copper and zinc alloys by formation of complex soluble ion Cation exchange with hydrogen zeolite, chlorination, deaeration, mixed-bed demineralization... 

Cations of these metals invariably exist in aqueous solution as complex ions. Consider, for example, the zinc(II) cation. In a water solution ofZn(N03)2, the Zn(H20)42+ ion is present. Treatment with ammonia converts this to Zn(NH3)42+ addition of sodium hydroxide forms Zn(OH)42-. 

Ammonia and sodium hydroxide are commonly used to dissolve precipitates containing a cation that forms a stable complex with NH3 or OH- (Table 16.2). The reactions with zinc hydroxide are typical ... 

This colour change can be observed with the ions of Mg, Mn, Zn, Cd, Hg, Pb, Cu, Al, Fe, Ti, Co, Ni, and the Pt metals. To maintain the pH constant (ca 10) a buffer mixture is added, and most of the above metals must be kept in solution with the aid of a weak complexing reagent such as ammonia or tartrate. The cations of Cu, Co, Ni, Al, Fe(III), Ti(IV), and certain of the Pt metals form such stable indicator complexes that the dyestuff can no longer be liberated by adding EDTA direct titration of these ions using solochrome black as indicator is therefore impracticable, and the metallic ions are said to block the indicator. However, with Cu, Co, Ni, and Al a back-titration can be carried out, for the rate of reaction of their EDTA complexes with the indicator is extremely slow and it is possible to titrate the excess of EDTA with standard zinc or magnesium ion solution. 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

The precipitate is soluble in free mineral acids (even as little as is liberated by reaction in neutral solution), in solutions containing more than 50 per cent of ethanol by volume, in hot water (0.6 mg per 100 mL), and in concentrated ammoniacal solutions of cobalt salts, but is insoluble in dilute ammonia solution, in solutions of ammonium salts, and in dilute acetic (ethanoic) acid-sodium acetate solutions. Large amounts of aqueous ammonia and of cobalt, zinc, or copper retard the precipitation extra reagent must be added, for these elements consume dimethylglyoxime to form various soluble compounds. Better results are obtained in the presence of cobalt, manganese, or zinc by adding sodium or ammonium acetate to precipitate the complex iron(III), aluminium, and chromium(III) must, however, be absent. 

Copper and brasses in the systems are more resistant to corrosion because of a stable oxide film however, if ammonia is present together with oxygen, corrosion of copper and copper oxide rapidly occurs. The corrosion is an oxidation process and results in the formation of the ammonia-copper complex [Cu(NH3)42+], Corrosion of nickel and zinc components also may occur in like fashion. 

Amino peptidases zinc, 6,606 Amino sugars metal complexes geochemistry, 6, 867 Ammonia... 

In 0-level qualitative analysis, unknown cations are identified by reacting them with aqueous sodium hydroxide and/or aqueous ammonia. For example, zinc salt solutions react with aqueous sodium hydroxide to form a white precipitate, zinc hydroxide, which in turn will react with excess aqueous sodium hydroxide to form a colourless solution of sodium zincate, a complex salt. However, 25% of the 915 students thought that when sodium hydroxide solution was added to a solution of a zinc salt, a displacement reaction resulted leading to the formation of a precipitate... 

C18-0033. Zinc oxalate, Zn(C2 O4), is sparingly soluble in water (Zjp = 1.4 X 10 ). The Zn ion forms a tetrahedral-shaped complex with ammonia. The formation constant for the complex is 4.1 X 10. How many moles of zinc oxalate will dissolve in 1.0Lof0.200M aqueous ammonia ... 

The detailed mechanism dictating the regulation of the process depends on the specific nature of the system, i.e., on the particular compound to be deposited, complexing agent, solution pH, film thickness, potential, etc. For example, in the case of the Cd-Se system, electroreduction of selenosulfate occurs at more positive potentials for either EDTA-ammonia- or NTA-complexed cadmium [13], whereas for ZnSe, the potential required for the reduction of selenosulfate is already reducing for zinc, implying thus a different mechanism. The metal complex has to be adequately stable and should not interfere with selenosulfate reduction. In these terms. 

Picric acid, in common with several other polynitrophenols, is an explosive material in its own right and is usually stored as a water-wet paste. Several dust explosions of dry material have been reported [1]. It forms salts with many metals, some of which (lead, mercury, copper or zinc) are rather sensitive to heat, friction or impact. The salts with ammonia and amines, and the molecular complexes with aromatic hydrocarbons, etc. are, in general, not so sensitive [2], Contact of picric acid with concrete floors may form the friction-sensitive calcium salt [3], Contact of molten picric acid with metallic zinc or lead forms the metal picrates which can detonate the acid. Picrates of lead, iron, zinc, nickel, copper, etc. should be considered dangerously sensitive. Dry picric acid has little effect on these metals at ambient temperature. Picric acid of sufficient purity is of the same order of stability as TNT, and is not considered unduly hazardous in regard to sensitivity [4], Details of handling and disposal procedures have been collected and summarised [5],... 

The zinc ion cross-links with the polymer to create sufficient strength and cross-linking density for durability and resistance to abrasion and detergents. The floor finish is easily removed with ammonia cleansers to reform the stable complex with zinc. The action of pulling the zinc out of the polymer allows the polymer to dissolve in the stripping solution. 

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... 

In these procedures 1 litre of seawater was shaken with 60 mg charcoal for 15 min. Complexing agents were added in amounts of 1 mg, dissolved in 1 ml of acetone. The pH was 5.5, or it was adjusted to 8.5 by addition of 0.1 M ammonia. The charcoal was filtered off and irradiated. Results of three sets of experiments with charcoal alone, charcoal in the presence of dithizone, and charcoal in the presence of sodium diethyldithiocarbamate are compared. The following elements are adsorbed to an extent from 75 to 100% silver, gold, cerium, cadmium, cobalt, chromium, europium, iron, mercury, lanthanum, scandium, uranium, and zinc. The amount of sodium is reduced to about 10 6, bromine to about 10 5, and calcium to about 10 2. 

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