PHOSPHINSUBSTITUIERTE CHELATLIGANDEN XXI. REVERSIBEL SUBSTITUTION VON TETRACARBONYL(PHOSPHINOTHIOFORMAMID)-KOMPLEXEN,(CO)4M (M = Cr, Mo, W), MIT TRIORGANOPHOSPHINEN, -ARSINEN UND -STIBINEN

Article abstract of DOI:10.1016/0022-328X(86)80281-9

To investigate the substitution of octahedral, neutral P,S-chelate complexes, the tetracarbonyl(phosphinothioformamide) compounds (M = Cr, (1), Mo (2), W (3); R¹ = Me, R² = H (A), R¹ = Ph, R² = H (B) and R¹ = R² = Me (C)) were treated with the ligands PPh3 (a), AsPh3 (b), SbPh3 (c), PEt3 (d) and P(OMe)3 (e).Unlike the corresponding phosphinothioformamidate 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 unidentate 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.