PREPARATION AND STRUCTURAL CHARACTERIZATION OF BIS(ACETYLACETONATO)RUTHENIUM(II)-BINAP - AN EFFICIENT ROUTE TO AN EFFECTIVE ASYMMETRIC HYDROGENATION CATALYST PRECURSOR

A simple one-pot synthesis of Ru(acac)(2)(S-BINAP) in near quantitative yield was achieved by the reduction of Ru(acac)(3) (acac=acetylacetonate) with activated Zn in the presence of S-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (S-BINAP). The X-ray diffraction study revealed the presence of two independent molecules of Ru(acac)(2) (S-BINAP) as well as three acetone molecules (solvent of crystallization) in the unit cell (monodinic, space group P2(1) with a = 15.681(5), b = 12.765(4), c =25.607(9) Angstrom, beta=98.16(3)degrees V=5074(3) Angstrom(3), Z=2, R=0.059 and R(w)=0.067). Each ruthenium(II) complex has a distorted octahedral geometry involving two phosphorus atoms of BINAP and four atoms of oxygen from two eta(2)-acac ligands. Although the conformation of the BINAP-containing seven-membered ring is delta in each molecule, both Lambda and Delta metal configurations are observed. The molecular structure has been compared with Ru(OCOR)(2)(BINAP) (OCOR=pivalate, tiglate) structures. Ru(acac)(2)(S-BINAP) was used to catalyze the asymmetric hydrogenation of 2-(6'-methoxy-2'-naphthyl)acrylic acid to yield S-naproxen in high optical purity.