Ru(O₂CCF₃)₂(PPh₃)₂ and ruthenium phosphine complexes bearing fluoroacetate ligands: synthesis, characterization and catalytic activity

Abstract

The dinuclear ruthenium(ii) phosphine complexes Ru2Cl(O2CCHxF3-x)3(PPh3)4(μ-H2O) (x = 0, 1, 2), containing fluoroacetate ligands, were prepared from RuCl2(PPh3)3 and NaO2CCHxF3-x in tBuOH. The X-ray characterization of these complexes reveals a bridging water molecule, stabilized by hydrogen bonds with the fluoroacetate ligands. The isolation of the complex Ru(O2CCF3)2(PPh3)2 is described, starting from RuCl2(PPh3)3 or Ru2Cl(O2CCF3)3(PPh3)4(μ-H2O) and TlO2CCF3, correcting the reported preparation in which Ru2Cl(O2CCF3)3(PPh3)4(μ-H2O) was obtained. Ru(O2CCF3)2(PPh3)2 easily reacts with CO, affording Ru(O2CCF3)2(CO)2(PPh3)2. The protonation of Ru(OAc)2(dppb) with trifluoroacetic acid in the presence of bidentate O and N donor ligands affords the complexes Ru(O2CCF3)2(dppb)(LL) (LL = ethyleneglycol, ethylenediamine), which are catalytically active in the transfer hydrogenation of ketones with 2-propanol. In the reduction of cyclohexanone, the glycol derivative displays a higher catalytic activity than the diamine complex, reaching a TOF of 22 000 h-1.