Carboxylation of (DPPF)-MCl2 [DPPF=1,1′-bis(diphenylphosphino)ferrocene; M=Pt or Pd] in aqueous and non-aqueous solution: Crystal and molecular structures of [Pt(C2O4)(DPPF)] and of [PtCl(NO3)(DPPF)]

Treatment of the complexes [MCl2(DPPF)] (M=Pt or Pd) {readily prepared in high yield from [MCl2(DMSO)2] (M=Pt (cis-) or Pd (trans-) and DPPF in CHCl3} with two molar proportions of AgNO3 in H2O did not give the expected cation [M(DPPF)(H2O)2]2+ in solution. Instead the unusual homobimetallic bridged complex [{M(μ-OH)(DPPF)}2](NO3)2 was formed as an insoluble solvolysis solid product. Hence, carboxylation by addition of carboxylate anions to the solution cannot be carried out by this method. In contrast, the complex [PtCl2(DPPF)] reacted readily with two molar proportions of AgOAc or one of Ag2{1,1′-(OOC)2fc} (fc=ferrocene-2H) in acetone to give the corresponding carboxylato complexes. Other carboxylato complexes were obtained from the reaction of the complexes [MCl2(DPPF)] and the K-salts of e.g. (COOH)2, CH2(COOH)2, and in H2O. With few exceptions, neither the K- nor the Ag-salts of the acids Me3CCOOH and C6H11COOH react completely with [MCl2(DPPF)] in aqueous or non-aqueous solutions. However, the required products were obtained by displacement of DMSO from the corresponding carboxylato complexes by DPPF in CHCl3. All of the new carboxylato complexes and the solvolysis products were characterized physicochemically and spectroscopically. The X-ray structures of [Pt{(OOC)2}(DPPF)] and of [PtCl(NO3)(DPPF)] were determined, to obtain some additional information on the coordination mode of the unsymmetrical DPPF ligand in this type of complexes.