239076-83-6Relevant academic research and scientific papers
Impact of the novel Z-acceptor ligand bis{(ortho-diphenylphosphino)phenyl}zinc (ZnPhos) on the formation and reactivity of low-coordinate Ru(0) centers
Beck, Madeleine L.,Burnage, Arron L.,Farmer, James C. B.,Isaac, Connie J.,Macgregor, Stuart A.,Mahon, Mary F.,Miloserdov, Fedor M.,Whittlesey, Michael K.
, p. 15606 - 15619 (2020/11/20)
The preparation and reactivity with H2 of two Ru complexes of the novel ZnPhos ligand (ZnPhos = Zn(o-C6H4PPh2)2) are described. Ru(ZnPhos)(CO)3 (2) and Ru(ZnPhos)(IMe4)2 (4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) are formed directly from the reaction of Ru(PPh3)(C6H4PPh2)2(ZnMe)2 (1) or Ru(PPh3)3HCl/LiCH2TMS/ZnMe2 with CO and IMe4, respectively. Structural and electronic structure analyses characterize both 2 and 4 as Ru(0) species in which Ru donates to the Z-type Zn center of the ZnPhos ligand; in 2, Ru adopts an octahedral coordination, while 4 displays square-pyramidal coordination with Zn in the axial position. Under photolytic conditions, 2 loses CO to give Ru(ZnPhos)(CO)2 that then adds H2 over the Ru-Zn bond to form Ru(ZnPhos)(CO)2(μ-H)2 (3). In contrast, 4 reacts directly with H2 to set up an equilibrium with Ru(ZnPhos)(IMe4)2H2 (5), the product of oxidative addition at the Ru center. DFT calculations rationalize these different outcomes in terms of the energies of the square-pyramidal Ru(ZnPhos)L2 intermediates in which Zn sits in a basal site: for L = CO, this is readily accessed and allows H2 to add across the Ru-Zn bond, but for L = IMe4, this species is kinetically inaccessible and reaction can only occur at the Ru center. This difference is related to the strong π-acceptor ability of CO compared to IMe4. Steric effects associated with the larger IMe4 ligands are not significant. Species 4 can be considered as a Ru(0)L4 species that is stabilized by the Ru→Zn interaction. As such, it is a rare example of a stable Ru(0)L4 species devoid of strong π-acceptor ligands.
2,2,2-Trifluoroethanol-assisted imine hydrogenation by a Ru-monohydride
Scodeller, Ivan,Salvini, Antonella,Manca, Gabriele,Ienco, Andrea,Luconi, Lapo,Oberhauser, Werner
, p. 242 - 247 (2015/06/02)
The trans heterodiphosphane Ru-based compound of the formula [Ru(OAc)2(CO)2(PnBu3)(PPh3)] proved to be a suitable precatalyst for imine hydrogenation in 2,2,2-trifluoroethanol (TFE) without the addition of an external base. High-pressure (HP) NMR investigations combined with a DFT-study, carried out on a related model precatalyst, were indicating the formation of a cationic Ru-monohydride-2,2,2-trifluoroethanol (TFE) species that catalyzes the imine hydrogenation by a TFE-assisted outer-sphere reaction mechanism.
Bis(methimazolyl)silyl complexes of ruthenium
Hill, Anthony F.,Neumann, Horst,Wagler, Joerg
, p. 1026 - 1031 (2010/04/25)
The new bis(methimazolyl)silane PhSiH(mt)2 (mt = methimazolyl), obtained from methimazole (Hmt) and phenyldichlorosilane, reacts with [Ru(η4-C8H12)(η6-C 8H10)] in refiuxing tetra
Chemoselective hydrogenation of α,β-unsaturated ketones to allylic alcohols, catalyzed by a mononuclear ruthenium complex containing trans PnBu3 and PPh3 ligands
Micoli, Francesca,Oberhauser, Werner,Salvini, Antonella,Bianchini, Claudio
, p. 2334 - 2341 (2008/01/27)
The ruthenium(II) bis(acetate) complex Ru(CO)2(OAc)2(PnBu3) (PPh3) (OAc = acetate) containing two different trans phosphine ligands, has been employed as pre-catalyst for the chemoselective hydrogenation of α,β-unsaturated ketones to allylic alcohols. Analogous catalytic reactions with the homodiphosphine pre-catalysts Ru(CO)2(OAc)2(PnBu3) 2 and Ru(CO)2(OAc)2(PPh3)2 gave lower conversions and selectivities. Batch catalytic reactions and operando high-pressure NMR experiments have contributed to establish that the hydrogenation of the C{double bond, long}O group is performed by the heterodiphosphine monohydride RuH(CO)2(OAc)(PnBu3)(PPh3) generated in situ by hydrogenation of the bis(OAc) precursor. PPh3 unfastening from this monohydride complex is an essential condition for the occurrence of catalytic activity.
Mononuclear ruthenium complexes containing two different phosphines in trans position: II. Catalytic hydrogenation of C{double bond, long}C and C{double bond, long}O bonds
Salvi, Luca,Salvini, Antonella,Micoli, Francesca,Bianchini, Claudio,Oberhauser, Werner
, p. 1442 - 1450 (2007/10/03)
Bis(acetate) ruthenium(II) complexes of the general formula Ru(CO)2(OAc)2(PnBu3) [P(p-XC6H4)3] (OAc = acetate, X = CH3O, CH3, H, F or Cl), containing different phosphine ligands trans to PnBu3, have been employed as catalyst precursors for the hydrogenation of 1-hexene, acetophenone, 2-butanone and benzylideneacetone. For comparative purposes, analogous reactions have been performed using the homodiphosphine precursors Ru(CO)2(OAc)2(PnBu3)2 and Ru(CO)2(OAc)2(PPh3)2. The catalytic activity of the heterodiphosphine complexes depends on the basicity of the triarylphosphine trans to PnBu3 as this factor controls, inter alia, the rate of formation of hydride(acetate), Ru(CO)2(H)(OAc)(PnBu3)[P(p-XC6 H4)3], or dihydride, Ru(CO)2(H)2(PnBu3)[(p-XC 6H4)3], complexes, by hydrogenation of the bis(OAc) precursors. The catalytic hydrogenation of the C{double bond, long}C double bond is best accomplished by homodiphosphine dihydride catalysts, while heterodiphosphine monohydrides are more efficient catalysts than the homo- and heterodiphosphine dihydrides for the reduction of the keto C{double bond, long}O bond.
Catalytic activity of dihydride ruthenium complexes in the hydrogenation of nitrogen containing heterocycles
Frediani, Piero,Pistolesi, Valentina,Frediani, Marco,Rosi, Luca
, p. 917 - 925 (2008/10/09)
The catalytic activity of the dihydride ruthenium complexes, RuH 2(CO)2(PnBu3)2, RuH 2(CO)2(PPh3)2 and RuH 2(PPh3)4, in the hydrogenation of nitrogen containing heterocycles has been tested by analyzing the influence of reaction parameters such as temperature, hydrogen pressure, catalyst concentration, on the rate and regioselectivity of the reaction. RuH2(PPh 3)4 shows a better catalytic activity with an 86.7% conversion of quinoline after 24 h at 100°C under a hydrogen pressure of 25 bar, while RuH2(CO)2(PPh3)2 and RuH2(CO)2(PnBu3)2 in the same conditions give a conversion of 37.1% and 35.6%, respectively. These results are confirmed by the reaction rate of the hydrogenation of quinoline, since the Kc in the presence of RuH2(PPh3) 4 (1.46 × 10-5 s-1) is higher than others (6.37 × 10-6 s-1 for RuH2(CO) 2(PPh3)2 and 6.36 × 10-6 s-1 for RuH2(CO)2(PnBu 3)2). Noteworthy is the selectivity of these catalytic systems in the hydrogenation of quinoline: in all tests the three catalysts lead to 1,2,3,4-tetrahydroquinoline as the major product, furthermore this compound is the only formed in the presence of RuH2(CO)2(PPh 3)2. The selectivity is affected by the presence of an acid (CH3COOH) or a base (NnBu3) in the reaction media. The complex RuH2(PPh3)4 is catalytically active, even if in a minor extent, in the hydrogenation of isoquinoline, pyridine and 2-methylpyridine. The basicity of the substrate and steric hindrance around the nitrogen atom show a great influence on the conversion. The results obtained suggest that the catalytic system activates a heterocyclic ring through the coordination of the heteroatom to the metal centre of the complexes.
Hydrogenation of single and multiple N-N or N-O bonds by Ru(II) catalysts in homogeneous phase
Toti, Alessandro,Frediani, Piero,Salvini, Antonella,Rosi, Luca,Giolli, Carlo
, p. 3641 - 3651 (2007/10/03)
The ruthenium(II) complexes RuH2(CO)2(P nBu3)2, RuH2(CO) 2(PPh3)2, and RuH2(PPh 3)4 are catalytically active in the hydrogenation of organic substrates containing a NN, N(O)N or NO2 group. The reduction of the first two groups leads to hydrazine as intermediate and amine as the final product, while reducing a NO2 group the corresponding amine is selectively formed. A complete conversion was reached, depending on temperature, catalyst and substrate concentration. The catalysts are also active in the hydrogenolysis of an N-N group giving the corresponding amine with a 97.3% conversion using RuH2(PPh3)4 as catalyst. A first-order reaction rate with respect to substrate, catalyst or hydrogen pressure was detected in all cases. Finally, the activation parameters and the kinetic constants of these reactions were calculated. In the hydrogenation of azobenzene, the rate determining step involves an associative or a dissociative step depending on the catalyst employed while in the hydrogenation of all other substrates an associative rate determining step is always involved. A catalytic cycle is suggested for the hydrogenation of azobenzene, taking into account the intermediate complexes identified in the reaction medium.
A combined parahydrogen and theoretical study of H2 activation by 16-electron d8 ruthenium(0) complexes and their subsequent catalytic behaviour
Dunne, John P.,Blazina, Damir,Aiken, Stuart,Carteret, Hilary A.,Duckett, Simon B.,Jones, Jonathan A.,Poli, Rinaldo,Whitwood, Adrian C.
, p. 3616 - 3628 (2007/10/03)
The photochemical reaction of Ru(CO)3(L)2, where L = PPh3, PMe3, PCy3 and P(p-tolyl)3 with parahydrogen (p-H2) has been studied by in-situ NMR spectroscopy and shown to result in two competing processes. The first of these involves loss of CO and results in the formation of the cis-cis-trans-L isomer of Ru(CO)2(L)2(H)2, while in the second, a single photon induces loss of both CO and L and leads to the formation of cis-cis-cis Ru(CO)2(L)2(H)2 and Ru(CO)2(L) (solvent)(H)2 where solvent = toluene, THF and pyridine (py). In the case of L = PPh3, cis-cis-trans-L Ru(CO)2(L) 2(H)2 is shown to be an effective hydrogenation catalyst with rate limiting phosphine dissociation proceeding at a rate of 2.2 s -1 in pyridine at 355 K. Theoretical calculations and experimental observations show that H2 addition to the Ru(CO)2(L) 2 proceeds to form cis-cis-trans-L Ru(CO)2(L) 2(H)2 as the major product via addition over the π-accepting OC-Ru-CO axis.
Isomerization of olefins by phosphine-substituted ruthenium complexes and influence of an 'additional gas' on the reaction rate
Salvini, Antonella,Piacenti, Franco,Frediani, Piero,Devescovi, Andrea,Caporali, Maria
, p. 255 - 267 (2007/10/03)
Phosphine-substituted ruthenium carbonyls have often been used as catalytic precursors in reactions such as the hydrogenation or the hydroformylation of olefins. To collect evidence on the coordination of the olefin as a preliminary step of these reactions we have investigated the isomerization of hex-1-ene, in hydrocarbon solvent, in the presence of the phosphine-substituted ruthenium carbonyls Ru(CO)3(PR3)2, Ru3(CO)9(PR3)3 and Ru(CO)2(OAc)2(PR3)2 [R=Bu, Ph]. When using Ru(CO)3(PPh3)2 the rate of the reaction shows a partial first order with respect to the concentration of the catalyst and of the substrate. The activation parameters were also evaluated and the activation entropy is negative. A reaction scheme involving the displacement of a carbonyl ligand with formation of a π-olefin-ruthenium complex is suggested. The rate of the reaction significantly changes if an alcohol is used as solvent. This behaviour is attributed to a modification of the catalytic precursor with formation of a ruthenium hydride. This hypothesis is confirmed by the identification of an alkoxy ruthenium hydride. The isomerization of olefins by phosphine-substituted ruthenium carbonyls is retarded by the presence of an 'additional gas' such as dinitrogen. This influence is more evident than the analogous one reported in the hydroformylation reaction: the same pressure of the 'additional gas' present in the reaction vessel reduces the rate of the isomerization to a larger extent, i.e. the presence of 1000 bar of nitrogen decreases in otherwise identical experiments the isomerization conversion of hex-1-ene from 95.6% to 25.8%. An analogous effect is also caused by the presence of argon and xenon. Helium, on the other hand, does not display any influence. These data are an indication of an interaction between the 'additional gas' and a catalytically active transition metal complex.
NMR detection of thermal and photochemical dihydrogen addition products of mono- and tri-nuclear ruthenium complexes containing carbonyl and triphenylphosphine ligands through para-hydrogen induced polarisation
Sleigh, Christopher J.,Duckett, Simon B.,Mawby, Roger J.,Lowe, John P.
, p. 1223 - 1224 (2007/10/03)
Enhancement of NMR signals by para-hydrogen induced polarisation is shown to facilitate the detection of isomers of Ru(CO)2(H)2(PPh3)2 and Ru(CO)3(H)2(PPh3) which contain inequiv
