Catalysts and Ligands

BINAP is the axially chiral bisphosphine that made asymmetric hydrogenation a production technology rather than a laboratory curiosity. It is sold as three separate products under three separate CAS numbers – racemic, (R) and (S) – and the three are physically indistinguishable on paper: same molecular formula, same molecular weight, same database identifier. That last

XPhos and SPhos are the two members of the Buchwald ligand family that most laboratories reach for first, they are usually quoted side by side, and they are routinely treated as near-substitutes. They are not. Look at the two structures and a single difference stands out: the groups attached directly to phosphorus are identical (dicyclohexyl

Phosphine ligand selection is usually taught as a list of names – XPhos for this, BINAP for that – which is why so many optimisation campaigns end up screening eight ligands and learning nothing. The ligands are not interchangeable brands. They differ along two axes that can be read off the structure before you run