Substitution Reactions of Inert-Metal Complexes—Coordination Numbers 6 and Above: Other Inert Centers
The coverage and arrangement of this chapter are very much the same as in previous volumes of this series. Although activity in some areas has diminished, it has undergone a comparable increase in others. Thus classical kinetic studies of substitution at, e.g., rhodium(III) and platinum(IV) centers have been rather rare during the period covered by this report. On the other hand, there has been increasing activity in substitution at the lower oxidation states of osmium, thanks largely to Taube’s novel studies, at ruthenium(II), largely in a photochemical context, and at technetium in various oxidation states, wholly in relation to the medical uses of a variety of its complexes. Perhaps the biggest increase in activity in the field defined by the title of this chapter has been in studies of systems in which ligand engineering has resulted in the dramatic slowing of substitution at normally labile centers. Such studies have often been impelled by the needs of radiotherapy, where a nucleus with specific radiochemical properties is required to be delivered to the site of action. An appropriate ligand is needed to transport the nucleus to its intended site, and of course it is necessary that this ligand shall not be lost en route if the metal ion happens to be substitution-labile. Uncharacteristically inert behavior of such centers as copper(II) and lanthanides(III) will be discussed in the following paragraphs, before the customary systematic treatment of the usual set of inert elements.