Influence of the rac–meso isomerization of seven-membered cyclic bisphosphines on the predominant formation of chelate complexes

The seven-membered cyclic bisphosphines 3–5 were synthesized by a Mannich-like condensation reaction of 1,2-bis(phenylphosphino)ethane, formaldehyde and primary amines (tert-butylamine, 1,1-(diphenyl)methylamine, (2R)-tetrahydro-2-furanylmethylamine) as a mixture of RPRP/SPSP (rac, 3a–5a) and RPSP (meso, 3b–5b) stereoisomers. The structures of the rac stereoisomers 3a–5a were investigated by X-ray crystal structure analyses. The RR/SS to RS isomerization of 3–5 and oxidation processes of 4 in solution were studied. Platinum(II) P,P-chelate complexes are formed exclusively from rac/meso mixtures of 3–5.

Novel seven-membered cyclic bisphosphines have been synthesized by Mannich-like condensation as a mixture of rac and meso stereoisomers. Potentially catalytic active P,P-chelate complex is exclusively formed by slow addition of metal to the isomeric mixture of ligand.Figure optionsDownload as PowerPoint slide