At one time the synthetic chemist's last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been supported by the discovery of new elementary reactions that occur at metal-heteroatom bonds and by the identification of factors that control these reactions. Together, these findings have led to new synthetic processes that are in daily use and have formed a foundation for the development of processes that are likely to be central to synthetic chemistry in the future.Organometallic complexes contain organic groups attached to a central metal through metalcarbon (M-C) bonds. These complexes undergo a set of elementary reactions, many of which release products containing new C-C or C-H bonds. The linking of these reactions to generate catalytic processes that form C-C bonds has been a recent focus of synthetic chemistry research. Such organometallic catalysts are now used to form C-C bonds in commodity chemicals (cheap chemicals sold in bulk) and polymers that are produced on the scale of millions of tonnes per year. They are also used in tailor-made polymers that are produced in small quantities and in highly intricate pharmaceuticals and biologically active natural products (see page 323), which are typically produced in milligram quantities for biological testing.The backbone of many organic compounds is composed of C-C bonds, but the function of these molecules is often derived from the presence of heteroatoms, such as nitrogen, oxygen and sulphur, which are held in these molecules by C-heteroatom bonds. For example, pharmaceuticals and conductive polymers (plastics that conduct electricity) often contain amine C-N bonds, and almost all natural products contain ether, ketone or ester C-O bonds. Heterocyclic compounds in which C-N, C-O or C-S bonds are present in the ring structure are found in all applications of chemistry. Moreover, useful intermediates in synthesis often contain C-B or C-Si bonds that are later converted into C-C, C-O or C-N bonds in the final products.Amines, alkoxides, thiolates and related reagents are common nucleophiles in reactions that occur without a catalyst. However, these reagents do not react with the weak electrophiles that are useful for synthesis, such as aromatic halides, and they do not react with common electronrich reagents, such as alkenes. Thus, the ability to carry out catalytic reactions that form these Correspondence should be addressed to the author (jhartwig@uiuc.edu). Author Information Reprints and permissions information is available at www.nature.com/reprints. The author declares no competing financial interests.
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