A catalyst increases the rate of a chemical reaction without itself being permanently changed by the reaction. The emphasis on permanently changed is important when discussing homogeneous catalysis because the catalyst does undergo chemical change in providing an alternative reaction pathway of lower energy. The ability to change oxidation state for transition metals makes them suitable as homogenous catalysts. A new activated complex is formed with the catalyst because transition metals can form stable compounds in more than one oxidation state and the transition metal ions can therefore readily move between oxidation states. During the catalysed reaction the transition metal (TM) ion is oxidised by one reactant to a higher oxidation state. This is then reduced back to the original form by reaction with the other reactant. The reactants are therefore converted to the same products as are formed without the catalyst. The only difference is that the reactants are converted into products more quickly.