very high regioselectivities for a number of terminal alkenes bearing various functional groups. In one case, the enantiomeric excess of a chiral product, i.e. a 3,5-dimethylhexa-1,4-diene derivative, was determined by chiral RP-HPLC to be 78% ee. The application of cobalt catalysts to the hydrovinylation of unsymmetrical alkenes and 1,3-dienes was investigated using modular phosphine-phosphite ligands