The production of low molecular weight oxygenates from carbon monoxide and ethene

Transition metal catalysed reactions of CO and ethene can lead to a variety of products ranging from small molecules to perfectly alternating long chain polyketones. In this review, we discuss the formation of small molecules with chain lengths up to 12 C atoms. Palladium based complexes of monodentate tertiary phosphines tend to give methyl propanoate under most conditions, but the selectivity can be varied by altering the electron donating power of the ligand or the nature of added acid co-catalysts. In addition to methyl propanoate, the major products can be co-oligomers, 3-pentanone or propanal. Using rhodium catalysts, the same products can be obtained, but the different selectivities depend upon the electron donating power of the ligand and the potential for chelate binding. In some cases, the extra H atoms required for the formation of 3-pentanone or oligoketones can be abstracted from the solvent, whereas in others they come from hydrogen formed by the water-gas shift reaction. The different reaction selectivities are discussed in terms of the reaction mechanisms operating. (C) 2002 Elsevier Science B.V. All rights reserved.