Heraeus Precious Metals has announced a number of advances in catalysts in recent months . Andrew Warmington reports
CATALYSTS
Catalytic conversions
Heraeus Precious Metals has announced a number of advances in catalysts in recent months . Andrew Warmington reports
Heraeus Precious Metals , one of the global leaders in the field , used a recent webinar entitled ‘ Optimising precious metal catalysts for finechem and pharmaceutical applications ’ to make a number of key announcements . These included a new ligand and a new development process , with a further new catalyst following shortly afterwards .
New ligand
The company developed its new phosphine ligand SabPhos ( Figure 1 ) in partnership with Ludwig Maximilians University in Munich . This is targeted at C-N couplings that were not feasible before . It currently incorporates a palladium-dba complex , but the company is working on using other precious metal supports in it .
“ The special feature of SabPhos ,” said Dr Detlef Gaiser , technical sales manager for homogenous catalysts and precious metal salts , “ is that it contains not only a phosphine but also a silicon , which pushes the electrons to the phosphorus and influences the electronic surroundings of the precious metal , in this case a palladium-dba complex .”
The conditions of the reaction when using this new catalyst are much milder than with a conventional bulky phospine ligand . It achieves an 88 % yield at 60 ° C in two hours , or 19 % at room temperature in three , whereas the traditional ligand takes 24 hours to reach 5 %. SabPhos also does not require the use of toluene as solvent . Heraeus already offers a variety of palladium-phosphine complexes in powder for many different C-C coupling reactions , including the Suzuki , Stille , Sonogashira , Negishi ,
Figure 1 – SabPhos ligand
Hyama and Heck reactions , as well as the Buchwald-Hartwig reaction for direct C-N bond formation in heterocyclic compounds . All are available in kilogram volumes . The company supplies homogeneous catalysts based on the six different platinum group metals ( PGMs ) of platinum , palladium , rhodium , ruthenium , iridium and osmium . In addition , it has access to the full variety of inorganic salts that come from these metals , including chlorides , nitrates and ammonium chlorides , which it develops in-house . These are also the starting materials for its heterogeneous catalysts .
New process
Artur Gantarev , technical sales manager for heterogeneous catalysts , said that Heraeus also offers heterogeneous catalysts for similar applications to homogeneous catalysts . These include chemicals , agrochemicals and pharmaceuticals , as well as for gas purification and specialised applications ranging from analytical equipment to satellite propulsion .
Depending on how they are synthesised , these catalysts can be supplied in powder and bulk forms , and in coatings , with the precious metal sitting outside or inside the support material ( Figure 2 ). The choice of precious metal precursor largely controls the behaviour and performance of the catalysts . These materials can also be of many types , such as activated carbon , alumina , silica , alumino-silicate ,
TiO 2 and zeolites , and their physical characteristics vary considerably .
“ Recently we have been getting more and more requests from customers who have been buying powder catalysts from us but want to have the same catalyst for use in a continuous reactor ,” Gantarev said . However , when the process changes , the customer cannot know at first what the final catalyst will look like and Heraeus has to support it in this journey .
In response , Heraeus has gained exclusive access to a new , specialised support material based on carbon microspheres . With this , it has been able to produce robust and mechanically stable catalysts that can be used in batch and continuous flow processes in tubes , capillaries or micro-structured devices . The catalysts can be used in fast and exothermic reactions and offer good process control and rapid reaction optimisation , said Gantarev .
JAN / FEB 2024 SPECCHEMONLINE . COM
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