Convenient synthesis of anionic dinuclear ruthenium(II) complexes [NR2H2][{RuCl(diphosphine)}2(μ-Cl)3] [diphosphine=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, 2,2′-bis(di(p-tolyl)phosphino)-1,1′-binaphthyl, and 1,2-bis(diphenylphosphino)benzene]:: crystal structure of [NEt2H2][{RuCl(1,2-bis(diphenylphosphino)benzene)}2(μ-Cl)3]

We report a practical one-pot synthesis of dialkylammonium salts of anionic dinuclear ruthenium complexes having chelating diphosphine ligands, BINAPs and DPB, with formula of [NEt2H2][{RuCl(diphosphine)}(2)(mu-Cl)(3)] [2a: diphosphine = 2.2'-bis(diphenylphosphino)-1,1'-binaphthyl; 6a: 2.2'-bis(di(p-tolyl)phosphino)-1,1'-binaphthyl; 8a: 1,2-bis(diphenylphosphino)benzene]. Treatment of cationic ruthenium complexes, [RuCl(eta(6)-p-cymene)(diphosphine)]Cl (4) with a slight excess of NEt2H2Cl (5a) afforded 2a, 6a, and 8a in quantitative yields. Similar reactions with various dialkylammonium salts 5b-f gave the corresponding salts, [NR2H2][{RuCl(diphosphine)}(2)(mu-Cl)(3)]. A one-pot mixture of BINAP or its derivative, [RuCl2(eta(6)-arene)](2), and NR2H2Cl produced salts of the anionic dinuclear complexes which can be applied as catalysts for the asymmetric hydrogenation of ketonic substrates such as acetol and methyl acetoacetate with high activity and high enantioselectivity. The anionic face-sharing bioctahedral structure of these complexes was confirmed by the X-ray analysis of 8a, which has two hydrogen bonds between two NH of the diethylammonium cation and two terminal chloro-ligands. (C) 2000 Elsevier Science S.A. All rights reserved.