When a transition metal-coordinated ligand, considered as donating two electrons (a 2e donor ligand, see Section 2.4.2), dissociates from the metal, the ligand itself does not change (e.g. neutral molecules such as NH₃ and CO). For such a ligand, dissociation and replacement by another 2e donor ligand are typical reactions in coordination chemistry. In contrast, for organometallic compounds, there are several characteristic reactions and most of them involve 1e donor ligand(s). Understanding these reactions is very important to master organometallic chemistry. This chapter will explain several basic reactions among many characteristic reactions of organometallic complexes.

Oxidative addition refers to the reaction in which a compound (A–B) having a covalent bond between A and B reacts with a transition metal fragment described as L_nM (L generally stands for a supporting ligand) to give L_nM(A)(B) with two ligands A and B. The general formula is expressed by eqn (6.1). Since this reaction is formally reversible, it may be written as an equilibrium. The reverse reaction is referred to as reductive elimination and will be discussed in Section 6.3.