CHIRAL PLATINUM(II) COMPLEXES WITH PHOSPHORUS DERIVATIVES OF THE AMINO-ACID L-PROLINE - NMR SPECTROSCOPIC AND X-RAY STRUCTURE INVESTIGATIONS OF THE CIS INFLUENCE OF TERTIARY PHOSPHORUS LIGANDS

The mononuclear complexes Pt(P-P')Cl-2 1-3, where P-P' are the chiral ligands nylphosphino-2-(diphenylphophinomethyl)pyrrolidine (S-promepho s), S')-1,1'-bis(diphenylphosphino)-2,2'-bipyrrolidine (S-bipyrphos) a nd phosphino-2-(diphenylphosphinoxymethyl)pyrrloidine (S-prolophos), w ere synthesized and investigated by NMR spectroscopy and X-ray structu re analysis. The cis influence on the platinum aminophosphine bond in 1-3 is characterized by the coupling constant (1)J(Pt-P-a) which is do minated by the Fermi contact term and varies mainly with the electron density in the platinum 6s valence orbital. The magnitude of the tis i nfluence is too small to be detected by X-ray analysis because Pt-P bo nd lengths vary only by about 1 pm. Complex 1 crystallizes in two diff erent molecular geometries, the six-membered chelate ring adopts eithe r a half-boat or a half-chair conformation. The seven-membered platinu m chelate 2 has a boat form. All conformations are fixed by the square planar platinum environment and the fused L-proline molecules. In bot h compounds the phenyl groups occupy isoclinal positions but not alter nating axial/edge and equatorial/face arrangements. (C) 1998 Elsevier Science B.V.