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 quantitativ e yield was achieved by the reduction of Ru(acac)(3) (acac=acetylaceto nate) with activated Zn in the presence of S-2,2'-bis(diphenylphosphin o)-1,1'-binaphthyl (S-BINAP). The X-ray diffraction study revealed the presence of two independent molecules of Ru(acac)(2) (S-BINAP) as wel l 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 a toms 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 molecul ar structure has been compared with Ru(OCOR)(2)(BINAP) (OCOR=pivalate, tiglate) structures. Ru(acac)(2)(S-BINAP) was used to catalyze the as ymmetric hydrogenation of 2-(6'-methoxy-2'-naphthyl)acrylic acid to yi eld S-naproxen in high optical purity.