Phosphinsubstituierte chelatliganden: XXI. Reversibel substitution von tetracarbonyl(phosphinothioformamid)-komplexen, (CO) 4M( ) M  Cr, Mo, W), mit triorganophosphinen, -arsinen und -stibinen

Abstract

To investigate the substitution of octahedral, neutral P,S-chelate complexes, the tetracarbonyl(phosphinothioformamide) compounds (CO) 4 MSC(NR 1R 2)P Ph 2 (M  Cr ( 1), Mo ( 2), W ( 3); R 1  Me, R 2  H ( A), R 1  Ph, R 2  H ( B) and R 1  R 2  Me ( C)) were treated with the ligands PPh 3 ( a), AsPh 3 ( b), SbPhP 3 ( b), ( c), PEt 3 ( d) and P(OMe) 3 ( e)_. Unlike the corresponding phosphinothioformimidate complexes with an anionic chelate ligand, no CO substitution occurs, but a nucleophilic cleavage of the metalsulfur bond under formation of the cis, trans-isomeric complexes with unindentage ligands. The position of the equilibrium depends on steric and kinetic factors. A further equilibrium of the cis-substituted complex and the previous chelate complex is established resulting from the reversible substitution process with increasing kinetic lability from tungsten to chromium. A dissociative mechanism of the chromium complexes starting from the trans form is also discussed. The tungsten complex 3aC shows ideal reversible conditions with complete re-chelation unaffected by isomerisation.