Substitutions on square-planar complexes

Square-planar complexes are very important for the metal ions Ni, Pd , Pt , Ir , and Au . By far the largest number of mechanistic studies have been done on Pt square-planar complexes, because they are very numerous and their substitution reactions proceed at rates that are easy to follow. 

Square-planar complexes are often formed when a metal has 8 electrons in d orbitals, as is the case with Pt , Pd , Au , Rh and Ir . Such square complexes are always spin paired (diamagnetic). The reactions of Rh and IP are very fast and have been therefore much less studied. On the other hand, the mechanistic information collected in reactions of the platinum(II) complexes can be in most cases applied to the square-planar complexes of other metals. 

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