Results for complexes

Comparison of results for complexes of tridentate amines R2N(CH2)2-NH(CH2)2NR2 show similar effects. With dien (R = H), rapid substitution of chloride in Pt(dien)Cl+ by bases occurs at room temperature however with Et4dien (R = Et) the reaction is considerably slowed, since the four ethyl groups crowd the metal above and below the plane of the molecule (Figure 3.82) making nucleophilic attack harder. Such a complex can be attacked more easily by a small nucleophile rather than a better nucleophile which happens to be larger [89],... 

The second problem involves the measurement of pKa values for carbonyl and thiocarbonyl derivatives. Grieg and Johnson (157) have pointed out that the measurement of pKa values for very weak bases (11) is an inaccurate and arbitrary process. Of particular difficulty for our purposes is the fact that different carbonyl derivatives may require different acidity functions. As a result of this situation, no attempt was made to make correlations of pKa data for carbonyl and thiocarbonyl derivatives with eq. (2). Because accurate pKa values can be measured for imines, these values were correlated with eq. (2), although the conformational problem remains. The imine sets were first studied by Charton and Charton (73), who correlated them with eq. (2). No correlations of data for carbonyl or thiocarbonyl derivatives with eq. (2) are extant in the literature. Bhaskar, Gosavi, and Rao (158) have reported that AG values for complex formation of substituted thioureas with iodine are a linear function of the Taft a values. Drago, Wenz, and Carlson (159) have reported similar results for complex formation between iodine and substituted amides. Oloffson (160) has reported a linear relationship between -AH for the complex of substituted N,N-dimethylamides with SbCls and the ffj constants. 

Table 23. A b initio results for complexes of anions with several water molecules... 

Particularly unreliable are chromatography results for complex environmental matrices where the retention time and peak resolution of individual target analytes are affected by matrix interferences from dozens of non-target compounds also present in the sample. For such samples, chromatographic identification and quantitation becomes questionable for the following reasons ... 

The GB/SA model also correlates quite well with experiment for the neutral solutes. As expected, the regression slope and intercept are also nearly ideal. Conversely, based on the four ions for which results have been reported, there seems to be a tendency to overestimate ionic solvation free energies, but definite conclusions cannot be drawn from so small a sampling. Whereas the available data span a larger range of functionality than do those from the SASA model, there is still a paucity of results for complex and polyfunctional solutes. It would be very interesting to see how robust the model is in such instances. 

The use of kinetic and thermodynamic approaches along with physicochemical and X-ray diffraction data, as well as their comparison with earlier results for complexes with synthetic macrocyclic ligands, have allowed one to make sufficiently well-grounded conclusions about the mechanisms of synthesis and decomposition of clathrochelates. 

Attempts at obtaining single crystals for X-ray structure determination have failed thus far. Low solubility of the complexes In solvents suitable for vapor pressure osmometry have made molecular weight determination difficult. One result for complex III, cls-Pta2Cl2/DHAQ, In acetone yielded a M.W. of 2270 gm/mole, vs a calculated M.W. from elemental analyses of 2006 gm/ mole. 

The results for complexes with HF presented in Table 17.7 support the latter statements. The H- C distances between H-atom of HF molecule and C-atoms of Lewis base are presented. For the CeHs- HF complex there are two distinctly shortest H- C distances of 2.505 and 2.503 A for C-atoms numbered as 4 and 5. The most negative charges are observed for these carbon atoms. In the other words the most important attractive electrostatic interactions exist for the shortest H- C contacts. This is very important that the bond path connecting two sub-units, HF and CeHe, links H-attractor with BCP lying on the bond path connecting 4 and 5 carbon attractors One can see that the bond path shows the preferable interaction [32],... 

However, in the normal growth pattern, the technology becomes progressively more complex. New catalysts, new multi-catalyst/multi-reactor processes, blending of various PO and additives result in complex structures, especially in terms of CCD, severely complicating their characterization. Certain combinations of POs may result in ambivalent results if only TREF or CRYSTAF is used. To obtain unequivocal results for complex PP or PE copolymer or blend, both TREF and CRYSTAF should be conducted. 

Table 2.11 Results for complexes based on ethanol and benzonitrile.

In Example 7 of the 429 patent a complex with the composition of MgjTi2Clj2( thyl acetate) exhibited an ethylene polymerization activity of 167,000 gPE/gTi at 10 atm ethylene, 3 atm hydrogen at 85°C and a 4 hr polymerization time, which was 50 times more active than the titanium-only complex TiCljiethyl acetate, demonstrating the importance of the magnesium compound in improving polymerization activity. Results for complexes based on ethanol and benzonitrile are shown in Table 2.11. 

Figure 1.2 (a) Results of 6-31G calculations for complexes of MVK and a water molecule. Six mtermolecular degrees of freedom were optimized. The two lowest-energy structures that were found are illustrated. AE is the binding energy for the complex relative to the separated molecules. (b) The 6-3IG results for complexes of the CPD-MVK transition state with a water molecule, as in (a). Reprinted with permission from reference [17]. Copyright 1994 American... 

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