Asymmetric Synthesis of Coordination Compounds: Back to the Roots. Diastereoselective Synthesis of Simple Platinum(IV) Complexes

A publication by Alexander P. Smirnoff in Helvetica Chimica Acta in 1920 [6] describes the first synthesis of a coordination species, i.e., of tris(propane‐1,2‐diamine‐κN1,κN2)platinum(4+) ([PtIV(pn)3]4+), where it was shown that the configuration of a chiral center in the ligand can influence the configuration at the metal. The present investigation of [PtIV(pn)3]4+ was carried out by NMR spectroscopy, where all nuclei in the metal complex were used as sources of information, i.e., 1H, 13C, 15N, and 195Pt. 13C‐NMR and 15N‐NMR spectroscopy (of isotopically enriched complex) were especially informative for the analysis of isomer distribution. Stereoselectivity in the formation reaction of the complexes is rather modest, whereas Δ‐, and Λ‐isomers can be separated efficiently by crystallization. A mixture of [Pt{(S)‐pn}3]4+ and [Pt{(R)‐pn}3]4+ shows no scrambling of the enantiomeric ligands, thus proving the inertness of the complexes.