CHAPTER 19 - Structure and Bonding in Coordination Compounds

Abstract

The chemistry of coordination compounds is a broad area of inorganic chemistry that has as its central theme the formation of coordinate bonds. A coordinate bond is one in which both of the electrons used to form the bond come from one of the atoms, rather than each atom contributing an electron to the bonding pair, particularly between metal atoms or ions and electron pair donors. Electron pair donation and acceptance result in the formation of a coordinate bond according to the Lewis acid-base theory (see Chapter 5 ). However, compounds such as H 3 N:BCl 3 will not be considered as coordination compounds, even though a coordinate bond is present. The term molecular compound or adduct is appropriately used to describe these “complexes” that are formed by interaction of molecular Lewis acids and bases. The generally accepted use of the term coordination compound or coordination complex refers to the assembly that results when a metal ion or atom accepts pairs of electrons from a certain number of molecules or ions. Such assemblies commonly involve a transition metal, but there is no reason to restrict the term in that way because nontransition metals (Al 3+ , Be 2+ , etc.) also form coordination compounds.