CATALYSTS
C-C coupling reactions
Another tool in synthesis is the ability to form C-C bonds directly via a C-C coupling reaction . This was long considered the holy grail of organic chemistry and became possible through homogeneous catalysis with palladium complexes . For the discovery of this class of reactions , chemists Akira Suzuki , Richard F . Heck and Ei-ichi Negishi were awarded the Nobel Prize for Chemistry in 2010 .
The impact of C-C couplings on the synthesis of complex drug molecules can hardly be overstated . Instead of long , linear synthesis chains , convergent syntheses can be used , in which individual sub-molecules are first built up and then joined together by means of a C-C coupling . This bears advantages in the selection of starting materials and optimises the overall yield .
Palladium complexes with various phosphine ligands are predominantly used as C-C coupling catalysts . Heraeus offers a selection of monodentate and bidentate phosphines that have strengths depending on the substrate . Chiral phosphines can also be used to specifically produce enantiomers .
Recycling catalysts
Whether they are homogeneous or heterogeneous , the recycling of precious metal catalysts should be an integral planning component of any chemical process from
Figure 2 - Precious metals cycle from production to recycling & trading
the outset . Indispensable for economic considerations alone , recycled precious metals also have a 98 % lower carbon footprint than newly mined ones .
Heraeus , like some others , achieves recovery rates of 90-99 % with its recycling processes , making the use of precious metal catalysts in this particularly economical . Thus , with recurring use , only low recycling losses need to be replaced . In this process , the precious metals are recovered by pyro- or hydrometallurgical processes down to the atomic level to metals with at least 99.95 % purity .
In addition to the recovery rate , other important criteria for the selection of a partner are transparent and auditable processes , as well as sufficient capacities in the region of the company ’ s own production .
The cross-border transport of waste containing precious metals presents its own challenges due to environmental regulations and customs requirements .
Capacities are also important because they determine how quickly the precious metal is available again for new products . In addition , the partner must also be able to supply the replacement quantities of precious metal reliably and in line with market requirements and meet compliance criteria and the necessary certifications .
One-stop offer
The procurement strategy of many companies is aimed at diversifying their supply chains – and not just since the recent geopolitical crises . Nevertheless , when selecting individual partners at all supplier levels , care should be taken to ensure that they can cover the whole precious metal cycle of procurement , use and recovery ( Figure 2 ).
With a distinctive international footprint , strategic partnerships and redundant production sites , leading precious metals experts thus make a significant contribution to securing their customers ’ supply chains . ●
Dominik Sperzel
GLOBAL HEAD OF SALES
HERAEUS PRECIOUS METALS k + 49 6181 35 - 5802 J dominik . sperzel @ heraeus . com j www . heraeus-precious-metals . com
20 ESTABLISHED 1981