LIGAND EFFECT ON THE INSERTION OF SNCL2 IN DICHLOROPLATINUM(II) COMPLEXES OF SYMMETRICAL AND MIXED AMINO(DO)PHOSPHINE-PHOSPHINITE CHELATES - X-RAY CRYSTAL-STRUCTURE OF PTCL2((S)-PH,CY-PRONOP)

The investigation of the structure of PtCl(SnCl3){AMPP}-type complexes resulting from the reaction in solution of SnCl2 with PtCl2{AMPP} com plexes (2a-h) (AMPP = aminophosphine-phosphinite chelates derived from (S)-(2-hydroxymethyl)pyrrolidine (1a-d), (S)-(2-hydroxymethyl)-5-pyrr olidinone (1e-g), and (1R,2S)-ephedrine (1h)) has been carried out by P-31 NMR spectroscopy. The formation of two isomeric complexes in whic h the trichlorostannato ligand is located trans to either the P(N) (3) or P(O) (4) moiety was observed. The relative ratio of complexes 3 an d 4 in the final reaction mixtures varied from 100/0 to 55/45 dependin g on the nature of the substituents on the P(N) and P(O) moieties of t he chelating phosphorus ligand. The results are analyzed in terms of t he relative P(N)/P(O) electron density and are connected to the cataly tic activities obtained previously in the asymmetric hydroformylation of styrene. The influence of steric factors is also discussed through the structural characterization by X-ray diffraction or PtCl2{(S)-Ph,C y-ProNOP}, the first platinum complex to contain a chiral chelating ph osphorus ligand bearing different aryl and alkyl substituents on its t wo phosphorus atoms.