Metal complexes play important roles as catalysts or other participants
in synthetic and biological reactions. Substrates and sometimes
attacking reagents also are activated through coordination with metal
atoms or ions. In these events the natures not only of the central
metals but also of ancillary ligands exert important influences on the
stability and reactivity of the coordinated substrates. A ligand in
general can adopt various coordination modes depending on its chemical
environment, thus functioning as a probe. The number of coordination
modes increases with increasing complexity of the ligand. In this book
it is shown that even the simplest mono- and diatomic ligands such as H,
CO, and N2 exhibit a variety of coordination modes, which are related to
their reactions. The thiocyanate anion is taken up as a representative
of the triatomic ambidentate ligands, and factors influencing the
preferences for N- und S-bonding are summarized. Coordination chemistry
of ß-dicarbonyl compounds is a highlight of this book. Acetylacetone,
one of the most familiar Werner ligands, is shown to favor -carbon and
n-allylic bonding in many instances. Its versatile behaviour in changing
coordination modes is revealed.