Although bimetallic compounds such as the mercury(1) halides
have been known for many years, it has been only in the last two decades
that chemists have become aware of the general importance of metalmetal
interactions in transition metal chemistry. Recently, however, it
has become apparent that the direct overlap of transition metal cation
d or d-hybrid orbitals in complexes often leads to the formation of
strong covalent bonds between the metal atoms, and it is the purpose
of this survey to review and enlarge upon current knowledge of and
opinions on this relatively new field of inorganic chemistry. Although
several reviews have appeared in recent years (1-3), these have either
dealt only with certain aspects of the field, or are outdated.