Dendritic polymers containing a dimethylsilyl linked dihydroxybenzyl alcohol backbone: divergent synthesis, aggregation, functionalization, and an evaluation of their applications in catalysis

Abstract

A divergent synthetic approach to the construction of dimethylsilyl linked dihydroxybenzyl alcohol based dendrimers via acid–base hydrolytic chemistry of bis(dimethylamino)dimethylsilane with 3,5-dihydroxybenzyl alcohol, is reported. The peripheral OH groups lead to significant aggregation that was studied using FT-IR and UV-Vis spectroscopies, light scattering and transmission electron microscopy. Different generations of dendrimers could be easily functionalized at the periphery with phosphorus donor groups that were subsequently bound to RhCl(1,5-C₈H₁₂). Such organometallic dendrimers were found to be active and recoverable catalysts for hydrogenation of decene. The catalytic efficiency was found to be dependent on the number of generations and reaction time. An uncontrolled reaction of Me₂Si(NMe₂)₂ with 3,5-dihydroxybenzyl alcohol in a multi-step addition process or one-pot reaction, led to the formation of hyperbranched polymers in which the build-up of the polymeric backbone was found to be dependent on the preferential reactivity and sterics at the benzylic center, as observed during dendrimer construction.