SYNTHESIS AND CHARACTERIZATION OF MONONUCLEAR AND TRINUCLEAR RUTHENIUM COMPLEXES OF 2,2'-BIS(DIPHENYLPHOSPHINO)-1,1'-BINAPHTHYL AND THEIR CATALYTIC ACTIVITY

The structures of ruthenium(II) complexes formed in solution from [RuX{(S)-binap}(arene)]Y (S)-3 (X, Y = halide and/or BF4-; binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; arene = benzene or p-cymene) depend on the solvent. In acetonitrile-methanol (1 : 1 dicationic complexes [Ru{(S)-binap}(MeCN)4]X(Y) (S)-4 (X = Y = Cl a; X = Cl, Y = BF4 b; X = Y = Br c; or X = Y = I d) are predominantly formed, while monocationic species [RuX{(S)-binap}(MeCN)3]X (S)-6 (X = Cl a, Br b or I c) were observed in acetonitrile. These mono- and di-cationic species could not be isolated pure, while [RuCl2{(S)-binap}(MeCN)2] (S)-5 was isolated from (S)-4a or (S)-6a upon concentration of the reaction mixture. In methanol without donor molecules such as acetonitrile, cationic trinuclear complexes [Ru3X5{(S)-binap}3]Y (S)-7 (X = Y = Cl a; X = Cl, Y = BF4 b or X = Y = Br c) were exclusively formed by heating at 60-degrees-C or UV irradiation of a solution of (S)-3. The structure of (S)-7 was characterized by spectral data and an X-ray crystallographic analysis of (S)-7b [orthorhombic, space group P2(1)2(1)2(1), a = 26.328(5), b = 18.140(3), c = 26.374(4), Z = 4, R' = 0.083]. The relationship between the structure of the Ru(II)(binap) complexes and their catalytic activities for asymmetric hydrogenation of methyl 3-oxobutanoate has been investigated.