The usage of aldehydes as basic building blocks is elementary for the chemical industry of most polymers. The annual production reaches scales of up to 10 million tons and is based on the conversion of olefins with CO and H2 (so called synthesis gas). Current methods either rely on the use of cobalt catalysts for longer-chained aldehydes as parts of the catalyst remain in the product and are therefore lost, or ligand-modified rhodium catalysts, which are separated easier from the product and therefore better recycled but only applicable for shorter-chained aldehydes.
Technical Description
The invention presented here tackles these problems by presenting a novel kind of general catalyst without classical ligands such as phosphines. His special feature is the introduction of a ligand comprising of N hetero cyclic silylenes coordinated at the rhodium central atom. These ligands possess a free pair of electrons at the silicium atom, modifiing the electronic properties of the metal site. The monosilylene ligands can be linked by spacers to give even bidentate ligands. Polydentate ligands offer a wide variaty of benefits like the formation of more stable complexes and thus more stable and active catalysts as well as the generation of a free coordination site at rhodium to capture and activate the olefine substrate. The large variaty of usable substituents which can be present in the bis-silylene ligands offer a wide range of adjustments of the catalyst for regioselective hydroformylation.
