Synthesis and characterization of mono- and tri-nuclear ruthenium complexes of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl and their catalytic activity

Abstract

The structures of ruthenium(l1) complexes formed in solution from [RuX{(S)-binap}(arene)]Y (S) -3 (X, Y = halide and/or BF,-; binap = 2,2'-bis(diphenylphosphino)-l,l '-binaphthyl; arene = benzene or p-cymene) depend on the solvent. In acetonitrile-methanol (1 :predominantly formed, while monocationic species [RuX{(S)-binap}(MeCN)JX ( S ) -6 (X = CI a, Br b or I c ) were observed in acetonitrile. These mono-and di-cationic species could not be isolated pure, while [RuCI,{(S)-binap}(MeCN),] (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 [Ru,X,{(S)-binap},JY (S)-7 (X = Y = CI a; X = CI, Y = BF, b or X = Y = Br c ) were exclusively formed by heating at 60 "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 P2,2,2,, a = 26.328(5), b = 18.1 40(3), c = 26.374(4), Z = 4, R' = 0.0831. The relationship between the structure of the Ru"( binap) complexes and their catalytic activities for asymmetric hydrogenation of methyl 3-28 Kyoto Program Package for X-Ray Crystal Structure Analysis, 233.

Continuous‐Flow Asymmetric Hydrogenation of the β‐Keto Ester Methyl Propionylacetate in Ionic Liquid–Supercritical Carbon Dioxide Biphasic Systems

“…Halide‐free complexes D 18 and E 19 were twice to ten times more active than complex B , respectively. Unfortunately, both complexes resulted in very low enantioselectivities and in the case of complex E even reversed enantioselectivity was achieved, again underlining the pivotal role of the halide co‐ligands for the catalyst performance 17b…”

Routes to dicationic ruthenium(II) nitrile complexes containing chelating diphosphine ligands: X-ray analyses of Ru(dppb)(MeCN)42+ 2PF6−(dppb = Ph2P(CH2)4PPh2) and trans-RuCl2(MeCN)4

“…Even the shorter Ru-N bonds, however, are slightly longer than -2.0 A, the sum of the estimated single covalent radii (17), implying little Ru(II)+N, d~-~T T backbonding. Where such backbonding is significant, shorter Ru-N bonds are observed, as, for example, in Ru(I1)-N, complexes: although the accuracy of crystallographic data for dinitrogen complexes is sometimes low, the more reliable Ru-N bond lengths of 1.822 (13) A (18) and 1.894 (9) A (19) in Ru-porphyrin and -bis(ethylenediamine) species, respectively, are significantly shorter than those in the Ru(I1)-nitriles. The C-N bond lengths in the four nitrile complexes range from 1.12 to 1.14 A, being slightly shorter than the value of 1.157 A calculated for MeCN in the gas phase (20), as commonly observed in both transition metal (21) and main group (22) complexes of nitriles.…”

“…2 We now report that the "extra" 3 1~ signal, in the case of the dppb system, results from the presence of Ru(dppb)-(M~cN),,', which is isolated and structurally characterized as the PF6 salt 3; the benzonitrile analogue (4) is also isolated, and structural details of 3 are compared with those determined also for trans-RuCl,(MeCN), (5), a previously known complex (7,8). It should be noted that the AB quartet assigned to a species of type 2 in the binap work (6) is not due to ~u ( b i n a~) (~h~~) ; + (see below); a ,'P singlet is expected for the latter complex (9).…”

Mechanistic Insights into Transition Metal‐Catalysed Oxidation of a Hydroxamic Acid with in situ Diels–Alder Trapping of the Acyl Nitroso Derivative

“…Upon the addition of BINAP to this suspension, the concentration of nitrosopyridine 21 dramatically decreased, while the concentration of the disproportionation product 26 appeared to increase. Nitroso species are known to be good oxidants [14] and, under the experimental conditions, nitrosopyridine 21 appears to be similar to molecular oxygen in its ability to carry out oxidations, which implies that Cu(I) is oxidised to Cu(II) under these reaction conditions. Furthermore, the natural tendency of nitrosopyridine 21 to disproportionate can be further enhanced by the presence of Cu(I).…”

“…Prompted by Yamamotos report that Cu(I)-BINAP complexes produced high ee in nitroso-Diels-Alder reactions [13] we have also decided to include in this study complexes 18 and 19 with analogous [14] and another ruthenium complex 17 containing a ligand with chiral phosphorus. [15] All of these complexes 12-20 were screened in the reaction and compared to the catalysts 4 at room temperature and at À78 8C.…”