Rhodium (Rh) complexes have high reactivity and selectivity and could be used in the hydroformylation of long chain alkenes to form aldehydes – an important industrial process. However, due to their difficult and costly recovery this particular use of Rh has been restricted.

Now, researchers at the University of St. Andrews, Scotland, have successfully used diphenylphosphine functionalised polyhedral oligomeric silsesquioxane (POSS) dendrimers (with 16 or 48 diphenylphosphine end groups) as ligands for the Rh catalysed hydroformylation of oct-1-ene (L. Ropartz, K. J. Haxton, D. F. Foster, R. E. Morris, A. M. Z. Slawin and D. J. Cole-Hamilton, J. Chem. Soc., Dalton Trans., 2002, (23), 4323–4334).

Unexpectedly high regioselectivity to the linear aldehyde (86%) was obtained with a POSS dendritic ligand (with a spacer of five atoms between the P atoms, and C-Si linkage). Small molecule analogues and other dendritic ligands had lower selectivity.