'Product Blog'
Phosphine Ligands for Hydroformylation Chemistry
Teaching an old dog new tricks
Hydroformylation is one of the oldest and most successful examples of industrial uses of catalysts. Over the last 50 years, several exciting technologies have been developed using primarily cobalt and rhodium as the metal, with a variety of different ligands. These include the very simple like triphenylphosphine, to much more complex ligands, such as dppBz and derivatives of 4,8-Dimethyl-2-phosphabicyclo[3.3.1]nonane (CYTOP® 170, Strem Catalog: 15-7605).
The successful implementation of these chemistries is a marriage of exciting innovation work at the discovery stage, the right partners, and access to the key chemicals and engineering required to make a commercial unit.
Access to a variety of bulky phosphines remains critical to homogeneous catalyst development. CYTOP® 170 (4,8-dimethyl-2-phosphabicylo[3.3.1]nonane CAS 328952-85-8) represents a bulky cyclic phosphine ligand that can be derivatized to make a variety of mono- and bidentate ligands for homogeneous catalysis – and is available commercially. Based on the limonene molecule, this secondary phosphine acts as a bulky precursor for phosphine ligands for use in catalysis.
CYTOP® 170 is used to synthesize hindered tertiary phosphine ligands via the addition of an olefin using free radical initiators (1). The P-H bond is easily accessible for chemical modification and as such, the chemical alteration via radical or other methods, proceeds readily. The resulting bulky tertiary phosphine ligands have been used for cobalt-catalyzed hydroformylation (2). In these cases, long alkyl chains such as 1-octadecene can be added to form effective and unique hydroformylation phosphine ligands. Complexation of the derivatives to cobalt of the two resulting diastereomers did not result in radically different hydroformylation rates or selectivity.
Recently, exciting publications have demonstrated the viability of medium pressure hydroformylation with cationic cobalt catalysts using bidentate phosphine ligands (3). Bidentate phosphine ligands can be produced from diphenylphosphine with a variety of backbones (aryl or alkyl) to make appropriate catalytic systems.
These new cationic cobalt catalysts are exceptionally stable, highly reactive and lead to high linear to branched (L:B) ratios for internal olefins. This chemistry proves there is a path to medium pressure hydroformylation based on the cobalt metal, and with many of the precursors commercially available, this closes one gap towards a commercial process.
While hydroformylation is an “old reaction”, this chemistry and others demonstrate there are still “new tricks” to be learned and taken advantage of.
CYTOP® 170 and CYTOP® 186 are clear, colorless, air sensitive pyrophoric liquids. They are powerful reducing agents and must be handled under an inert atmosphere.
To learn more about other ligands for catalysis, please refer to the Solvay offering in the Strem Catalog or on the Solvay website.
References:
Featured Products:
15-7605 4,8-Dimethyl-2-phosphabicyclo[3.3.1]nonane, min. 90%, CYTOP® 170
15-1705 Diphenylphosphine (43-47%) in high purity trioctylphosphine, CYTOP® 186TOP (Please Inquire)
Related Products:
Phosphorus Ligands and Compounds Booklet
All products sold in collaboration with Solvay
