Complex metal-chloro

Galena, sphalerite and chalcopyrite precipitate also due to increase of pH due to the breakdown of base metal chloro complexes accompanied by the boiling by the... 

Table 4.5 Extraction of metal chloro complexes into diethyl ether... 

Under typical freshwater conditions, at pH 7-9 and in presence of millimolar concentrations of carbonate, most transition metals in solution (Cu(II), Zn(II), Ni(II), Co(II), Cd(II), Fe(TII), etc.) occur predominantly as hydroxo or carbo-nato complexes. For a few metals, chloro complexes may be predominant (Ag(I), Hg(II)), if chloride is in the range 10-4—10-3 mol dm-3 or higher. Alkali and alkali-earth cations occur predominantly as free aquo metal ions [29], At lower pH values, the fraction of free aquo metal ions generally increases. Strong sulfide complexes of several transition metals have recently been shown to occur even under oxic conditions [32,33]. 

An even more serious problem can arise when dissolved species expected to predominate at high temperatures are undetectable at 25°C or are only present at concentrations which are too low for them to be adequately characterized thermodynamically. Examples are certain transition metal chloro-complexes (9,10) and mixed complexes of such metals with hydroxide and another ligand (11,12). Thus it seems that chloride complexing so alters the aqueous chemistry of copper and gold that supposedly inert gold components in autoclaves are reversibly oxidized by Cull (10) and it is likely that mixed oxine and hydroxy complexes of Fell contribute considerably to the gross under-estimation (by a factor of up to 10 ) of magnetite solubility in oxine (12,14). 

Immobilization of Organorare-Earth Metal Chloro Complexes... 

The existence of the PGM and gold in the form of complex anions in chloride media has been used to advantage in the design of several solvent-extraction processes. Thus, metal-chloro complexes of the type MCI/- can be extracted by, for example, salts of secondary amines ... 

TABLE 13.3 Redox Potentials for H2(C18TPP) and for Its Metal/Chloro Complexes in H2CC12... 

The details of the cupric salt reaction with the palladium adduct are not clear. Exchange to form a cupric alkyl is one possibility or complex formation,"probably with chloride bridges between the palladium adduct and cupric chloride, may occur with subsequent anion shift from palladium to carbon or perhaps an Sn2 displacement of the complex metal group by an anion may occur. Rearrangements producing 1,3 and 1,4 substituted products from linear olefins have also been observed. For example, 1-butene produced several percent of 1,3- and 1,4-chloro acetates and diacetates under the reaction conditions used 16>. "Hydrido-palladium acetate or chloride" -complexes would seem to be likely intermediates in these arrangements. 

Decomposition of complex metal organic molecules are t3 ically endothermic reactions performed in furnace reactors. An example of a furnace decomposition is the thermal decomposition of dimethyl— chloro-silane to give silicon caihide [6] ... 

Susak, N. J. (1981). Spectra, Thermodynamics and Molecular Chemistry of Some Divalent Transition Metal Chloro-Complexes in Hydrothermal Solution at 30(PC, Ph.D. Thesis. Princeton, New Jersey Princeton University. 

The solubility of PbS and ZnS in waters containing dissolved chloride is enhanced by the formation of metal-chloro complexes MeCl, MeCl , MeClJ, and MeCl4. Most fluids that have concentrations of dissolved lead and dissolved zinc exceeding 1 mg also have chlor-... 

Anion exchangers such as the IonPac AS5 are also suited for the analysis of com-plexed transition metals and heavy metals, which opens another field of application for ion chromatography. Examples of respective chromatograms for the separation of metal-EDTA complexes as well as for metal-chloro complexes are displayed in Figs. 3-78 and 3-79. 

Fig. 3-79. Separation of various metal-chloro complexes. - Separator column IonPac AS5 eluent 0.2 mol/L NaC104 + 0.2 mol/L HC1 flow rate 2 mL/min detection UV (215 nm) injection volume 50 pL solute concentrations 0.2 ppm Pt, 2 ppm Pb, 5 ppm Au, and Fe.

One area that utilises the strengths of INS is that of transition metal chloro complexes. Most of the transition metals form chloro complexes and a wide variety of geometries is known. The most common are tetrahedral, square planar and octahedral. These have been extensively studied by infrared and Raman spectroscopies [4] and largely assigned. However, both Oh octahedral and D4h square planar complexes have an internal mode that is infrared and Raman inactive (vg Tau and V5 5au respectively). There are also inactive lattice modes. 

Table 5. Metal centred reduction potentials of Fe(III), Mn(III) and Cu(II) complexes of chloro (N-substituted 5,10,15,20-tetraphenylporphyrin). (The numbers in parentheses are AEpa Pc in volts)...

Figure 40. Is NEXAFS spectra of in transition metal-chloro complexes, (a) Cl NEXAFS spectrum of a transition metal-chloro complex showing the pre-edge and the main edge region (modified from Shadle et al. 1994). The energy of the main absorption edge is very close to that of uncomplexed aqueous . (b) and (c) shows the Cl NEXAFS spectra of different transition metal chlorides (A) Fe(III), (B) Fe(II), (C) Co(II), (D) Ni(II), (E) Cu(II) (modified with permission from Shadle et al. 1995. American Chemical Society).

Hybrid catalysts derived from cocondensation of Group 8 metal-chloro complexes with Si(OEt)4 via a sol-gel process were highly active for the synthesis of A/,iV-dimethyIformamide from CO2, H2 and dimethylamine under supercritical conditions, affording turnover numbers up to 100800 at 100% selectivity [61]. The activity of the catalysts, containing methylphosphine ligands, decreased in the order Ru>Ir>Pt,Pd>Rh. It seemed that the high activity of silica matrix stabilized ruthenium complexes was due to the formation of an active hydride intermediate by hydrogenolysis of the Ru-Cl bond. 

Direct detection has gained great significance in determination of nitrite and nitrate,as well as bromide and iodide in the presence of high chloride concentrations. Moreover, chromate, sulfide, thiocyanate, thiosulfate, and selected metal chloro- and cyano-complexes can be determined by means of this method. 

---