Rhodium catalyzed hydroformylation: Adventures in heterogeneous and recyclable systems

The synthesis of dendritic ligands supported on silica gel and polymers, and their use in the rhodium catalyzed hydroformylation reaction is presented in this thesis. In building a softer, more organic moiety on the surface of a heterogeneous support, the potential of uniting the advantages of heterogeneous catalysis with that of homogeneous systems is explored.; The synthesis of polyamidoamine (PAMAM) dendrimers anchored on silica, via the iterative additions of methylacrylate and ethylenediamine to aminopropyl silica, is carried out. A series of C4, C6 and C12 diamines were also used to construct PAMAM dendrimers with longer diamine linkers. Phosphanylation of the various PAMAM dendrimers on silica was accomplished and the supported bis-(diphenylphosphanylmethylated) ligands were complexed to rhodium.; The heterogeneous complexes were found to be effective catalysts for the hydroformylation of various aryl olefins and vinyl esters, showing good to excellent regio-selectivity for the branched aldehydes. Aliphatic olefins were also easily converted into the corresponding aldehydes, however, only a slight excess of the linear product was observed.; Rhodium complexes of bis-(diphenylphosphanylmethylated) pseudopeptide based ligands immobilized on resin were prepared and studied in the hydroformylation of various olefins. The effect of relocating the metal centers from the periphery to the interior of the dendrimer was also examined.; The recyclability of the aforementioned heterogeneous catalysts was investigated, however, leaching of the metal from the support and the accompanying loss of activity is observed.; The synthesis of PAMAM and polyarylether ligand supported on PEG was attempted. The preparation of a soluble triphenylphosphite supported on PEG was also attempted and the crude system was evaluated as a recyclable ligand for the hydroformylation of 1-octene. Preliminary investigations into the activity of the zwitterionic (eta6-C6H5BPh 3)-Rh+(1,5-cyclooctadiene) complex with phosphite under mild hydroformylation conditions resulted in a surprising regioselective outcome where the industrially more important linear aldehyde of 1-octene was favoured with high selectivity.