User:Msjlink/4.6.1 Dissociative mechanism

Dissociative mechanism is one of substitutional reactions metal complexes undergo to change their substituent ligands. Octahedral metal complexes with 18 electrons frequently go through dissociative mechanism to exchange their ligands as they are in the stable state having s,p and d orbitals filled with electrons. In order for an octahedral complex to coordinate a new ligand, one of its substituents has to be initially released. The 16 electron intermediate metal complex forms distorted trigonal bipyramid or square pyramid depending on characteristics of its other ligand substituents. Ligands that are strong ɑ donors or π accepters lead a metal complex to form a square pyramid geometry as they produce large Δo. On the other hand, ligands that are strong π donors create a distorted trigonal bipyramid to form due to small Δo. In the square pyramid metal complex, a new ligand is coordinated to the place where the initial ligand departed. Alternatively, a new ligand is introduced inversely to the departed ligand in the trigonal bipyramid. The rate law for the dissociative mechanism is shown below.