Synthesis of Ruthenium Carbonyl Complexes with Phosphine or Substituted Cp Ligands, and Their Activity in the Catalytic Deoxygenation of 1,2-Propanediol

A ruthenium hydride with a bulky tetra-substituted Cp ligand, (CpiPr4)Ru(CO)2H (CpiPr4 = C5(i-C3H7)4H) was prepared from the reaction of Ru3(CO)12 with 1,2,3,4-tetraisopropylcyclopentadiene. The molecular structure of (CpiPr4)Ru(CO)2H was determined by X-ray crystallography. The ruthenium hydride complex (C5Bz5)Ru(CO)2H (Bz = CH2Ph) was similarly prepared. The Ru−Ru bonded dimer, [(1,2,3-trimethylindenyl)Ru(CO)2]2, was produced from the reaction of 1,2,3-trimethylindene with Ru3(CO)12, and protonation of this dimer with HOTf gives {[(1,2,3-trimethylindenyl)Ru(CO)2]2-(μ-H)}+OTf −. A series of ruthenium hydride complexes CpRu(CO)(L)H [L = P(OPh)3, PCy3, PMe3, P(p-C6H4F)3] were prepared by reaction of Cp(CO)2RuH with added L. Protonation of (CpiPr4)Ru(CO)2H, Cp*Ru(CO)2H, or CpRu(CO)[P-(OPh)3]H by HOTf at −80 °C led to equilibria with the cationic dihydrogen complexes, but H2 was released at higher temperatures. Protonation of CpRu[P(OPh)3]2H with HOTf gave an observable dihydrogen complex, {CpRu[P-(OPh)3]2(η2-H2)}+OTf − that was converted at −20 °C to the dihydride complex {CpRu[P(OPh)3]2(H)2}+OTf −. These Ru complexes serve as catalyst precursors for the catalytic deoxygenation of 1,2-propanediol to give n-propanol. The catalytic reactions were carried out in sulfolane solvent with added HOTf under H2 (750 psi) at 110 °C.