Ligand values

Figure 6.2. A comparison of the stabilities of the Cu(n) complexes of open-chain and macrocyclic ligands values are for water at 25 °C with / = 0.1 or 0.5 mol dm-3.

The i>c=0 of the complexes of PA with lanthanides occurs at 1662 cm-1 and does not show a shift from the free ligand value in the solid state (59). The small shift in i>c=o 1S due to the fact that the C=0 group of the free ligand is involved in hydrogen bonding in the solid state. However, in acetonitrile solution, the hydrogen bonds break and the i>c==0 °f the pure ligand appears at 1690 1. This value indicates a shift of 30 cm-1 in the vc=o of the complexes. 

In the case of complexes of lanthanide nitrates with CP (239), the infrared spectra exhibit two uCz=Q vibrations apart from a single pP=0- The J>p=o and one of the c=o vibrations occur at frequencies lower than the corresponding ligand frequencies But the second r>c=0 1S not much shifted from the free ligand value. These observations have been interpreted in terms of Structure VIII containing both coordinated... 

Sometimes 3(d — n ) and k ) states are said to be derived from delocalized orbitals and d—d) state from localized orbitals. The shift of the chelate emission from that of the free ligand increases in the sequence Rh(III) < Ir(III) < Ru(II) and reflects increasing cf-orbital participation in the emission orbital. The decrease in the chelate emission lifetime from the free ligand values also reflect the contamination of the molecular orbitals with d-character. The role of metal complexes as quenchers of excited states of it-electrons in organic compounds can be rationalized from such considerations. Emission from Cr8+ is the basis of one of the most important solid state laser system, the Ruby laser (Figure 10.14). 

The oxidative addition reaction of I2 with (> -Cp )2Ln (Ln = Sm °" , Eu ° , Ybio.ii) j,ggj3 utilized as a thermodynamic anchor to determine absolute Ln-X bond disruption energies, D(Ln-X), in solution. Suitable thermodynamic cycles can be set up in which the ability to estimate an accurate value for >(Ln-I) is crucial to the accurate calculation of D(Ln-X) for various carbon- and silicon-donor ligands . Values for D(Ln-I) are obtained from reactions such as the one for Sm, where n (probably) equals 2 or 3 ° ... 

Figures in parentheses are the complex-free ligand values,...

Attention was also drawn to the net increase in shielding for phosphite complexes of Cu , Ag, Ni" and Hg as the formal positive charge became larger (see Table XIX), whereas the corresponding zerovalent nickel complex [NiPJ (P = phosphite) showed a downfield shift from the free ligand value. Since Ni , Cu , Ag and Hg" all have electronic... 

O.OOSA) is indeed very similar to the free ligand value. On the other hand, the nickel-phosphorus distance (2.099 O.OOSA) is very much shorter than the values reported in other phosphine-nickel complexes, which suggests that the metal-phosphorus bond in Ni(PF3)4 may indeed have significant -character. A u-bond order of one has been estimated from the magnitude of the Co- P coupling constant in the [Co(PF3)4] ion (191). ... 

The P-F bond length is very similar to the free ligand value, and the nickel-phosphorus bond length is very short indeed since the normally accepted covalent radius of phosphorus is 1.1 OA and that of atomic... 

Figure 10.10. Analogs of spirosulfonamide and other P450 2D6 ligands. values were estimated by spectral...

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