Radical additions of diethyl- and diphenylphosphine have been used to prepare 1st and 2nd generation dendrimers based on polyhedral oligosilsesquioxane cores by a divergent synthetic method. The 1st generation dendrimer is built on either 16 and 24 vinyl or allyl arms formed by successive hydrosilation and vinylation or allylation of vinyl-functionalised polyhedral silsesquioxanes. Successive hydrosilation/allylation followed by hydrosilation/vinylation and addition of phosphine produce the 2nd generation dendrimer. The dendrimers have been used as ligands for the hydrofornlylation of oct-1-ene catalysed by [Rh(acac)(CO)(2)]. Using the alkylphosphine-containing dendrimers as ligands, alcohols (nonan-1-ol and 2-methyloctanol) are obtained, whilst the diphenylphosphine counterparts lead to the formation of aldehydes (nonan-1-al and 2-methyloctanal). Linear to branched ratios of 3/1 are obtained for the diethylphosphine compounds while ratios of 12 to 14/1 are given by the diphenylphosphine dendritic molecules. (C) 2002 Published by Elsevier Science B.V.