Transition Metal Catalysts
The transition metals are the group of metals in the middle section of the periodic table. They are divided into three groups - the first row transition metals, the second row transition metals and, guess what, the third row transition metals. Many of the transition metals behave as catalysts, either as the metal itself or as a compound. Below are some of the common reactionscatalysed by transition metals.
The important thing about catalysts is that they are recovered at the end of the reaction in their entirety, they are not used up during the reaction. They often undergo a temporary change during the reaction, but are turned back into the original chemical at the end of the reaction.
Catalysts change the rate of a reaction, but do not alter the position of equilibrium.
Although the yield within a short time seems more, the overall yield from the slow reaction would eventually be the same, but as it can take ages to get that far we usually don't wait that long.
Transition metal catalysts are either homogeneous catalysts or heterogeneous catalysts.
Homogeneous catalysts are those in the same physical phase as the other reactants e.g. all in solution together in the same solvent, or all are gases.
Heterogeneous catalysts are those in a different physical phase to the rest of the reactants. E.G. two different liquids in contact with catalysis occurring at the interface between them, or more commonly a solid catalyst and a solution, or a solid and gases
the transition metals and their compounds take part in the reaction as cata lysts as they can be obtained at the end of the reaction in the original state. The most important reason transition metals are good catalysts is that they can lend electrons or withdraw electrons from the reagent, depending on the nature of the reaction. The ability of transition metals to be in a variety of oxidation states, the ability to interchange between the oxidation states and the ability to form complexes with the reagents and be a good source for electrons make transition metals good catalysts.
Chemists believe that the catalytic activity of transition metals depends on their ability to exist in different oxidation states or co- ordination states.