Homogeneous catalysis is the success story of organometallic chemistry. Otto Roelen's initial discovery of hydroformylation in 1938 not only entailed large-capacity production plants but was later followed by systematic research into the catalytic chemistry of the ever-growing class of organometallic compounds. Further developments in industrial chemistry towards clean, low-temperature, low-pressure, and economic processes - in feedstock or in the fine chemicals and polymer area - clearly depend on improved catalysts. Molecularly defined, tailor-made structures are the safest prerequisites for chemical selectivity; hence, organometallic compounds with their overwhelming variety of compositions and structures offer the most promising approach. Wilkinson's catalysts [HRh(CO){P(C6H5)3}3] and [ClRh{P(C6H5)3}3] are outstanding ex-amples. On the other hand, process technology has to be considered also (for example catalyst-product separation and heat-exchange problems). The following review attempts to critically assess the future trends and present demands in the applied area of organometallic catalysis - a "gentle art" that is far from being a mature field.
