Complexation anionic

They are prepared by the action of HNO2 on aromatic amines. The amine is dissolved in excess of mineral acid and sodium nitrite is added slowly until a slight excess of HNO2 is present. The reaction is usually carried out in ice-cold solution. The solution then contains the diazonium salt of the mineral acid used, anhydrous diazonium salts of unpredictable stability may be precipitated with complex anions like PF , SnCl6 BF4 . 

Complexes. These derivatives contain complex anions which may be considered as derived from co-ordination of an H" ion to a metal or non-metal. Examples are the BH4" and ReHg " ions. 

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

If the coordination entity is negatively charged, the cations paired with the complex anion (with -ate ending) are listed first. If the entity is positively charged, the anions paired with the complex cation are listed immediately afterward. 

Aqueous solutions of caustic soda aie highly alkaline. Hence caustic soda is ptimatily used in neutralization reactions to form sodium salts (79). Sodium hydroxide reacts with amphotoric metals (Al, Zn, Sn) and their oxides to form complex anions such as AlO, ZnO. SnO ", and (or H2O with oxides). Reaction of AI2O2 with NaOH is the primary step during the extraction of alumina from bauxite (see Aluminum compounds) ... 

These compounds perform a dual function in synthesis procedures. The introduction of a complex anion assists in the stabilization of the desired product and the generation of unique intermediates by chloride displacement, eg, silver hexafluorophosphate, AgPF, forms adducts with neutral diamagnetic organometaHics which can act as controUed sources of highly reactive cations (29). Silver hexafluoroantimonate, AgSbF, is an electrophilic... 

Iron hahdes react with haHde salts to afford anionic haHde complexes. Because kon(III) is a hard acid, the complexes that it forms are most stable with F and decrease ki both coordination number and stabiHty with heavier haHdes. No stable F complexes are known. [FeF (H20)] is the predominant kon fluoride species ki aqueous solution. The [FeF ] ion can be prepared ki fused salts. Whereas six-coordinate [FeCy is known, four-coordinate complexes are favored for chloride. Salts of tetrahedral [FeCfy] can be isolated if large cations such as tetraphenfyarsonium or tetra alkylammonium are used. [FeBrJ is known but is thermally unstable and disproportionates to kon(II) and bromine. Complex anions of kon(II) hahdes are less common. [FeCfy] has been obtained from FeCfy by reaction with alkaH metal chlorides ki the melt or with tetraethyl ammonium chloride ki deoxygenated ethanol. 

Kinetics. Details of the kinetics of polymerization of THF have been reviewed (6,148). There are five main conclusions. (/) Macroions are the principal propagating species in all systems. (2) With stable complex anions, such as PF , SbF , and AsF , the polymerization is living under normal polymerization conditions. When initia tion is fast, kinetics of polymerizations in bulk can be closely approximated by equation 2, where/ is the specific rate constant of propagation /is time [I q is the initiator concentration at t = 0 and [M q, [M and [M are the monomer concentrations at t = 0, at equiHbrium, and at time /, respectively. 

Alkali sihcates are used as components, rather than reactants, in many appHcations. In many cases they only contribute partially to overall performance. Utility factors are generally not as easy to identify. Their benefit usually depends on the surface and solution chemical properties of the wide range of highly hydrophilic polymeric siUcate ions deUverable from soluble sihcate products or their proprietary modifications. In most cases, however, one or two of the many possible induences of these complex anions cleady express themselves in final product performance at a level sufficient to justify their use (102). Estimates of the 1995 U.S. consumption of sodium sihcates are shown in Table 6. 

After preparing a homogeneous solution of the precursors, powder precipitation is accompHshed through the addition of at least one complexing ion. For PLZT, frequently OH in the form of ammonium hydroxide is added as the complexing anion, which results in the formation of an amorphous, insoluble PLZT-hydroxide. Other complexing species that are commonly used are carbonate and oxalate anions. CO2 gas is used to form carbonates. Irrespective of the complexing anion, the precipitated powders are eventually converted to the desired crystalline oxide phase by low temperature heat treatment. 

In this work, the results of study of zinc thiocyanate complexes anion-exchange extraction by non-symmetric QASes in toluene ai e discussed. The non-symmetric QASes have the common formula [(C,3H g03)N(CH3) (C,H Q3 J-X-, where C,3H3 03 - highly lipophilic substituent, (2, 3, 4-tn. s-dodecyloxy)benzyl. It was found that exchange... 

Other finite-complex anions occur in the oxyfluorides. For example the hydrated salts K2[- S2F]q0].H20 and Rb2[As2F]oO].H20... 

Figure 13.12 Schematic representation of the structure of the complex anion LSbjCIiiO] " showing the two different coordination geometries about Sb and the unique quadruply bridging Cl atom.

In all the cluster compounds discussed above there are sufficient electrons to form 2-centre 2-electron bonds between each pair of adjacent atoms. Such is not the case, however, for the cationic bismuth species now to be discussed and these must be considered as electron deficient . The unparalleled ability of Bi/BiCb to form numerous low oxidation-state compounds in the presence of suitable complex anions has already been mentioned (p. 564) and the cationic species shown in Table 13.12 have been unequivocally identified. 

The complex anion [ScFe] " has already been mentioned and, while there is a fairly extensive series of halo complexes with a... 

All the tetrahalides, but especially the chlorides and bromides, behave as Lewis acids dissolving in polar solvents to give rise to series of addition compounds they also form complex anions with halides. They are all hygroscopic and hydrolysis follows the same pattern as complex formation, with the chlorides and bromides being more vulnerable than the fluorides and iodides. TiCU fumes in and is completely hydrolysed by... 

There is also clear evidence of a change from predominantly class-a to class-b metal charactristics (p. 909) in passing down this group. Whereas cobalt(III) forms few complexes with the heavier donor atoms of Groups 15 and 16, rhodium(III), and more especially iridium (III), coordinate readily with P-, As- and S-donor ligands. Compounds with Se- and even Te- are also known. Thus infrared. X-ray and nmr studies show that, in complexes such as [Co(NH3)4(NCS)2]" ", the NCS acts as an A -donor ligand, whereas in [M(SCN)6] (M = Rh, Ir) it is an 5-donor. Likewise in the hexahalogeno complex anions, [MX ] ", cobalt forms only that with fluoride, whereas rhodium forms them with all the halides except iodide, and iridium forms them with all except fluoride. 

The coordination chemistry of Zn" and Cd", although much less extensive than for preceding transition metals, is still appreciable. Neither element forms stable fluoro complexes but, with the other halides, they form the complex anions [MX3] and [MX4] , those of Cd" being moderately stable in aqueous solution. "" By using the large cation [Co(NH3)6] + it is also possible to isolate the trigonal bipyramidal [CdCls] "... 

With both these pseudo halides, an excess produces complex anions [HgX3] and the tetrahedral [HgX4]2-. 

Several carboxylates, both simple salts and complex anions, have been prepared often as a means of precipitating the An ion from solution or, as in the case of simple oxalates, in order to prepare the dioxides by thermal decomposition. In K4[Th(C204)4].4Fl20 the anion is known to have a 10-coordinate, bicapped square antipris-matic structure (Fig. 31.8b). -diketonates are precipitated from aqueous solutions of An and the ligand by addition of alkali, and nearly all are sublimable under vacuum. [An(acac)4], (An = Th, U, Np, Pu) are apparently dimorphic but both structures are based on an 8-coordinate, distorted square antiprism. 

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