Polycationic complexes tend to form ion pairs with anions and these ion pairs often undergo reactions via the I pathway. The electrostatically held nucleophile can exchange positions with a ligand in the first coordination sphere, resulting in net substitution.  An illustrative process comes from the "anation" (reaction with an anion) of chromium(III) hexaaquo complex:
::[Cr(HO)]  +  SCN    {[Cr(HO)], NCS}
::{[Cr(HO)], NCS}     [Cr(HO)NCS]  +  HO