Ligand indicator

The IR stretching frequencies o(SN) and o(SF) occur at higher wave numbers and the S-N and S-F distances are significantly shorter in the octahedral cations [M(NSF)6] than those in the free ligand, indicating an increase in S-N and S-F bond strength upon coordination. 

The difference between the two extremes is essentially that, in the former, the Re retains its valence electrons in its d orbitals whereas in the latter it loses 6 of them to delocalized ligand orbitals. In either case paramagnetism is anticipated since rhenium has an odd number of valence electrons. The magnetic moment of 1.79 BM corresponding to 1 unpaired electron, and esr evidence showing that this electron is situated predominantly on the ligands, indicates that an intermediate oxidation state is involved... 

Scheme 1 Six main coordination modes (a-f) of the amino acid ligands indicated by the Harris notation, [63] where M is the transition metal ion...

Mapping of the ligand indices Z= 1... m of permutation isomers onto their skeletal indices s = l,. .., m) indicates which ligand occupies which skeletal site. The standard mapping with matching pairs of indices... 

In the representation of configurations by a mapping of ligand indices one must take into account the fact that in ligand sets containg indistin-... 

Pi upon the ligand indices. Thus, Pi and Ps are equivalent as permutation descriptor of configurations. 

Normally, the stereochemical features of the reaction type and the starting materials determine the stereochemical features of the products. Accordingly one can derive the operator T from E and R, and thus the transformation C - C. Such a representation requires a correlation of the ligand indices of the stereochemical representation used and the indices of the atoms that enter the representation of the constitution. 

These considerations lead, for example, to the assignment of a predominantly outer sphere character to Cl, Br, F, CIO3, NO3, sulfonate, and trichloro-acetate complexes and an inner sphere character to F", IO3, SO, and acetate complexes of trivalent actinides and lanthanides. The variation in AH° and AS° of complexation of related ligands indicates that those whose pA), values are <2 form predominantly outer sphere complexes, while those for whom > 2 form predominantly inner sphere complexes with the trivalent lanthanides and actinides. As the pK increases above 2, increasing predominance of inner sphere complexation is expected for these metals. 

The kinetics of removal of iron(III) from its complexes with the aminocarboxylate-anthraquinone analytical reagent calcein and with the antitumor anthracycline doxorubicin by l,2-dimethyl-3-hydroxy-4-pyridinone (LI, (251) with R = R = Me) have been monitored. Rate constants for metal removal are almost independent of the concentration of the replacing ligand, indicating dissociative mechanisms they are approximately 1 x 10 s for displacement from doxorubin and between 12 x 10 s and 2 x 10 s from calcein. 

The same effect is noted for the dimer in Figure 12c and 12d, but it is attenuated because the ipio-carbon is only coupled to two lithium cations. The Uneshape of the TMEDA ligand indicates that, again, a dynamic process occurs. This complex was included in the investigation of dynamic processes previously alluded to and discussed below in Section n.E . 

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