Synthesis, Structural Characterization and Catalytic Activity of Indenyl Complexes of Ruthenium Bearing Fluorinated Phosphine Ligands

The synthesis, characterization and  catalytic activity  of new  ruthenium  complexes of fluorinated triarylphosphines is described. The new ruthenium complexes [RuCl(ind)(PPh 3 ){P( p -C 6 H 4 CF 3 ) 3 }] and [RuCl(ind)(PPh 3 ){P(3,5-C 6 H 3 (CF 3 ) 2 ) 3 }] were synthesized in 57% and 24% isolated yield, respectively, by thermal ligand exchange of [RuCl(ind)(PPh 3 ) 2 ], where ind = indenyl ligand η 5 -C 9 H 7− . The electronic and steric properties of the new complexes were studied through analysis of the X-ray structures and through  cyclic voltammetry . The new complexes [RuCl(ind)(PPh 3 ){P( p -C 6 H 4 CF 3 ) 3 }] and [RuCl(ind)(PPh 3 ){P(3,5-C 6 H 3 (CF 3 ) 2 ) 3 }] and the known complex [RuCl(ind)(PPh 3 ) 2 }] differed only slightly in their steric properties, as seen from comparison of  bond lengths and angles  associated with the ruthenium center. As determined by cyclic voltammetry, the  redox potentials  of [RuCl(ind)(PPh 3 ){P( p -C 6 H 4 CF 3 ) 3 }] and [RuCl(ind)(PPh 3 ){P(3,5-C 6 H 3 (CF 3 ) 2 ) 3 }] are +0.173 and + 0.370 V vs. Cp 2 Fe 0/+ , respectively, which are substantially higher than that of [RuCl(ind)(PPh 3 ) 2 ] (−0.023 V). After activation through  chloride  abstraction, the new complexes are catalytically active in the  etherification  of propargylic alcohols (8–24 h at 90 °C in  toluene , 1–2 mol% catalyst loading, 29–61% isolated yields). As demonstrated by a comparative study for a test reaction, the three precursor complexes [RuCl(ind)(PPh 3 ){P( p -C 6 H 4 CF 3 ) 3 }], [RuCl(ind)(PPh 3 ){P(3,5-C 6 H 3 (CF 3 ) 2 ) 3 }] and [RuCl(ind)(PPh 3 ) 2 }] differed only slightly in catalytic activity.