With Complex Formation

The excess Gibbs free energies are positive for these systems, indicating positive deviations from Raoult s law as these polar and nonpolar molecules are mixed. But H is negative over most of the concentration range for the first of these systems and over the entire concentration range for the second, indicating 

The negative support this conclusion, since one would expect the formation of a complex to shrink the volume of the system. Temperature should have a significant effect on the formation of the complex by shifting the point of equilibrium in the reaction. Thus H and Sjj should be very temperature-dependent. This is verified by the large positive for the (dioxane+- 

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Metal carbonyls react with diazirines with complex formation at one or both N atoms (75JOM(94)75). The 1 2 complex (187) is converted to (188) by N —N cleavage in acidic media. 

Figure 34. Dissolution of metal through a metal oxide layer with complex formation.

Figure 35. Amplitude factor of the symmetrical fluctuation for anodic dissolution through a metal oxide layer with complex formation. Dm = 1.0 x 10-9 m2 s-1, Jt = 1.0 x 10"5 nr s-1 mol-1, m = 2, m = 2 1.Curves 1,2, and 3 correspond to the surface concentrations of the anion, (C (jr, yt 0)) = 10, 50, and 100 mol m-J, respectively.

The adsorption of ligands (anions and weak acids) on metal oxide (and silicate) surfaces can also be compared with complex formation reactions in solution, e.g.,... 

The temperature dependency of 1,2 content shown in Table II is also consistent with complex formation between polybutadienyl-lithium and the oxygen atom in the lithium morpholinide moleculre. One can visualize an equilibrium between noncom-plexed and complexed molecules which would be influenced by temperature. Higher temperatures would favor dissociation of the complex and, therefore, the 1,2 content of the polymer would be lower than that from the low temperature polymerization. This explanation is supported by the polymerization of butadiene with lithium diethylamide, in which the microstructure of the polybutadiene remains constant regardless of the polymerization temperature (Table IV). This is presumably due to the fact that trialkylamines are known to be poor... 

Other physical phenomena that may be associated, at least partially, with complex formation are the effect of a salt on the viscosity of aqueous solutions of a sugar and the effect of carbohydrates on the electrical conductivity of aqueous solutions of electrolytes. Measurements have been made of the increase in viscosity of aqueous sucrose solutions caused by the presence of potassium acetate, potassium chloride, potassium oxalate, and the potassium and calcium salt of 5-oxo-2-pyrrolidinecarboxylic acid.81 Potassium acetate has a greater effect than potassium chloride, and calcium ion is more effective than potassium ion. Conductivities of 0.01-0.05 N aqueous solutions of potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, sodium carbonate, potassium bicarbonate, potassium hydroxide, and sodium hydroxide, ammonium hydroxide, and calcium sulfate, in both the presence and absence of sucrose, have been determined by Selix.88 At a sucrose concentration of 15° Brix (15.9 g. of sucrose/100 ml. of solution), an increase of 1° Brix in sucrose causes a 4% decrease in conductivity. Landt and Bodea88 studied dilute aqueous solutions of potassium chloride, sodium chloride, barium chloride, and tetra-... 

In Section III, A the catalytic action of A1C13 and BBr3 on the thermal decomposition of thiatriazoles was mentioned. This effect is evidently connected with complex formation between a thiatriazole and a Lewis acid since the catalytic activity is lost on addition of compounds that complex more effectively with the Lewis acid.19 It is remarkable that titanium tetrachloride, in contrast to this, does not catalyze decomposition, but instead forms a thermally stable, orange 1 1 complex with 5-phenylthiatriazole.19 The complex is sensitive to atmospheric moisture and is hydrolyzed in high yield to the starting thiatriazole on addition of water. 

Stability constants associated with complex formation correspond to two successive steps as shown in Scheme 6.190 The constants for the formation of 1 1 and 2 1 complexes of the smaller alkali cations are comparable to those of the lone macrocycles [1.1] for complexes of (52). Very stable complexes are formed by the alkaline earth cations with this ligand (log 7 in H20).,9° The larger macrocycles of (53a-d) form alkali metal and alkaline earth complexes in which the stabilities of the 1 1 complexes are similar to those of the model V-methylated monocycle. The stabilities and selectivities of the 2 1 complexes are also similar to those of the 1 1 complexes. In fact, KS2 for incorporation of a second Ba2+ into (44a) is as high as KS] for the same ligand.190 Such findings indicate two essentially independent macrocyclic units. 

The thermodynamic parameters were calculated and are summarized in Table III. Both enthalpy and entropy decrease considerably with complex formation. Such a large decrease in enthalpy and entropy has not been found in other complex formation systems. For example, the change in enthalpy with the complex formation because of hydrophobic interactions generally is not so large and change in entropy is positive (23,24) and change in enthalpy with the complex formation in enzymatic hydrolysis of cellulose is slightly positive (25). These unusual decreases in enthalpy and entropy are inferred to be characteristics of the present complex formation system. 

Mixtures With Complex Formation In some instances, mixing of two liquids causes the formation of a chemically bonded complex in the mixture. One would expect that the formation of the complex should result in a significant lowering in energy and hence, a large negative HExamples are shown in Figure 17.1018 for mixtures of tetrachloromethane with N,N-dimethylformamide (DMF) and with 1,4-dioxane. 

Chrome dyes (see Section 3.11.2) are selected acid dyes that form complexes with chromium ions. With complex formation a strong bathochromic shift of shade occurs. In addition, as a result of the superposition of several excited states, a marked dulling of the hue is observed. 

The Sn—C bond frequencies are rather less sensitive to electronic effects in methyltin halides and depend weakly on either the number or the nature of the halogens. The increases associated with complex formation are also insignificant. Vibrational spectroscopy is a good tool not only for studying the spatial arrangement and ionicities of Sn—X bonds but also for measur-... 

No activation (energy) barrier separates the donor and the acceptor from the ET products (and vice versa). The electron transfer in Scheme 18 is not a kinetic process, but is dependent on the thermodynamics, whereby electron redistribution is concurrent with complex formation. Accordingly, the rate-limiting activation barrier is simply given by the sum of the energy gain from complex formation and the driving force for electron transfer, i.e. ... 

All anions which bind to the Cu(II) in galactose oxidase lower the gzz and Azz values (22). This is consistent with (but not required for) a blue shift in the d-d transitions (32, 33, 34). Fe(CN)63" is the only anion among the limited ones we have studied which produces a red shift in the optical bands (Figure 4). At 1 1, 5 1, or 100 1 molar ratios of Fe(CN)63" to enzyme the same difference absorbance spectrum is obtained, and it is consistent with complex formation between galactose oxidase and the anion. Namely, the positive difference peaks at 455, 830,... 

Several observations indicate the formation of starch-protein complexes. For instance, starch precipitates serum proteins of rabbit, horse, sheep, and chicken.962 This observation seemingly indicates that the complexation has a rather universal character. On the other hand, the type of bonding of proteins from Triticum durum and Triticum sativum is specific for each of these varieties.963 The observed effects may not be associated with complex formation, but they can instead be attributed to the destruction of micelles by dehydration, followed by agglomeration.964 As in the case of starch complexes with sugars, the effect of proteins and cellulose derivatives on starch gelation can be assumed to be the result of the competition for water in solution. As a consequence, swelling is perturbed.965-968... 

Consider complex ion formation in the CdClj-KCl system, and let it be assumed for the moment that a CdCl complex ion is formed. If such complex ions were formed in an aqueous solution of CdClj and KCl, they would exist as little islands separated from other ions by large expanses of water. In fused salts, there are no oceans of solvent separating the ions. Thus, a Cd " ion would constantly be coming into contact on all sides with chloride ions, and yet one singles out three of these CP ions and says that they are part of (or belong to) a CdCIJ complex ion (Fig. 5.54). It appears that in the absence of the separateness possible in aqueous solutions, the concept of complex ions in molten salts is suspect As will be argued later, however, what is dubious turns out to be not the concept but the comparison of complex formation in fused salts with complex formation in aqueous solutions. 

Concerning the interactions between olefins and hydrogen halides, we must first refer to the reports dealing with complex formation. Among these, we will recall the classical work of Cook et on the freezing-point diagrams of mixtures of HCl... 

Complex formation and hydrolysis of complexes. In acidic solutions, hydrolysis of group 5 elements is competing with complex formation. For group 5 complexes, it is described by the following equilibrium ... 

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