Synthesis, structure and hydroformylation activity of monomer rhodium and iridium pyrimidine thiolate complexes

The reaction of dinuclear [M(mu -Cl)(COD)](2) (M=Rh, Ir) with mercaptopyrimidine and its methylated derivatives affords monomeric complexes. Depending on the nature of the solvent used, the pyrimidine behaves as both a monodentate ligand, bonded to the metal directly through the sulfur atom, and as a bidentate ligand, bonded to the metal atom through both the sulfur and a nitrogen atom, acting as a chelating ligand. Reaction of these complexes with CO yields dicarbonyl complexes through displacement of the COD ligand. Displacement of one of the CO molecules occurs in the presence of PPh3. Both rhodium and iridium phosphinated complexes may accept a second PPh3 molecule within their coordination sphere, with no displacement of the remaining CO ligand. Thiolate rhodium complexes have proved to be good catalysts in the hydroformylation reaction of 1-heptene in the presence of PPh3. The donor capacity of mercaptopyrimidine ligands has been correlated with the activity of the catalysts tested. In the present work, an increase in ligand basicity gave rise to a faster reaction. However, no significant modifications in the distribution of the final products were observed.