Novel diazaphospholidine terminated polyhedral oligomeric silsesquioxanes in styrene and vinyl acetate hydroformylation: Synthesis and molecular dynamics studies

New diazaphospholidine POSS macromolecules have been synthesised and tested in styrene and vinyl acetate hydroformylation. Whilst some of them have shown activity, others precipitated upon mixing with the rhodium precursor preventing its efficient use. Molecular dynamics has been used to help understand these observations. Rigid and compact dendritic structures with phosphine groups engineered to have low mobility but high probability of sitting at distances favouring bidentate coordination with the rhodium precursors are necessary for the macromolecular ligands to be active. More flexible structures having lower probability of phosphine separations suitable for bidentate complex formation are more prone to form oligomeric dendritic species and hence to crosslink the macromolecules and precipitate.