The following is basically a copied and pasted slice from my first year PhD report introduction and will be added to and adapted at a later date.

Almost all of the chemical reactions and conversions that occur in the human body and the rest of nature are enzymatically catalysed. Catalysis also forms the backbone of the chemical industry with almost every product requiring a catalyst at some stage in it’s manufacture. Catalytic processes allow more efficient production than stoichiometric processes. By maximising the use of feedstocks and other reagents, processes are made more economically viable and more environmentally friendly. With a world wide market worth trillions of dollars, chemical catalysis is of the upmost importance to industry. The definition of a catalyst as proposed by Wilhelm Ostwald in c.1895 states that:

"A catalyst is a substance that increases the rate of approach to equilibrium of a chemical reaction without being substantially consumed in the reaction."

Catalysis by Transition Metals.

The chemical properties of transition metal complexes make them ideal for catalysis and are wildly exploited by industry.4-8 The lability of ligands or the use of coordinatively unsaturated complexes provide vacant sites on metals at which substrates can bind (e.g. olefins, CO). Transition metals also have a range of stable oxidation states between which transitions are relatively easily made. These properties combine to allow transition metals to bind and activate substrates (e.g. by oxidative addition of molecules such as H2, alkyl halides), to facilitate their chemical conversion and then eliminate products (e.g. via reductive elimination), cycling between stable oxidation states.

Transition metals are used throughout industry in many processes in both heterogeneous systems (e.g. particle of elemental metal dispersed on alumina or other inert support) and homogeneous systems (soluble transition metal complexes reacting with substrates in solution).

Homogeneous Catalysis versus Heterogeneous Catalysis.

Both types of catalysis have their advantages and disadvantages and which type is used is dependant on the nature and conditions of the process. Heterogeneous catalysts have two main advantages over homogeneous catalysts.2 The operational lifetime of heterogeneous catalysts are generally quite long whereas homogeneous catalyst can have quite variable lifetimes before catalyst replacement is required. The economics of catalyst recycling and retrieval is also much cheaper for heterogeneous processes as a solid supported catalyst can simply be filtered from the reaction mixture. Removal of a homogeneous catalyst from the reaction mixture can be difficult and expensive.

Homogeneous catalysts have many advantages over heterogeneous systems however. They tend to have much higher activity (with respect to the metal) and higher selectivity in comparison to heterogeneous systems whose performance can be quite variable. They also operate under much milder conditions and have a much lower sensitivity to catalyst poisoning. Diffusion of substrate through the catalyst to available reactive sites can be a problem for supported catalyst, but not for a soluble catalyst. One of the major advantages of homogeneous systems is the ability to probe the catalytic cycle to gain a detailed mechanistic understanding of the process, something more or less impossible for heterogeneous systems. From this, careful choice of ligands allows the electronic and steric properties of the metal centre to be tuned, maximising the efficiency of the process.

Probable topics to be covered:

• Homgenous catalysis
  • Acid/Base catalysis
  • By Transition metal complexes
  • Industrial applications
• Hetergeneous catalysis
  • Haber process
  • Polymer supported catalysts
  • liquid-liquid biphasic catalysis