17 research outputs found
Chemistry of ruthenium(II) alkyl binap complexes : novel bonding, cyclometalation, and P-C bond splitting
No full textReactions of the bis-isopropyl and bis-cyclohexyl alkyl Binap ligands, 8 and 9, respectively, with [RuCl2(eta(6)-p-cymene)](2) afford new dinuclear chloro-bridged Ru compounds which contain the Binap ligands as six- rather than four-electron donors. A backbone double bond proximate to one of the P-donors complexes the metal atom. NMR details of the olefin bonding plus isomerization reactions involving loss of the olefin complexation are reported. Reactions of 8 or 9 with [Ru(OAc)(2)(eta(6)-p-cymene)] result in slow P-C bond cleavage and cyclometalation, instead of affording the anticipated [Ru(OAc)(2)(Binap)] complex. The new cyclometalated complexes, 15 and 16, contain the complexed R2P-O(C=O)CH3 ligand and arise (presumably) via acetate attack at phosphorus with the electrons in the P-C bond moving to the ruthenium atom. The solid-state structure of one of these, the cyclohexyl analogue, 16, is reported and represents a rare structural example of a molecule with three different chelate ligands. The complexed R2P-O(C=O)CH3 ligand is readily hydrolyzed in wet triflic acid to afford the R2P(OH) donor and an eta(6)-arene ligand (via Ru-C protonation)
Piano-stool inversion in arene complexes of Ru(II) : modelling the transition state
No full textIn the solid-state, the [RuH(arene)(Binap)]CF3SO3, complexes, 1, arene = eta(6)-benzene and 2, arene = eta(6)-toluene, distort markedly from a classical three-legged piano-stool structure with the former having the P-Ru-P plane approximately perpendicular to the plane of the arene; this structure for 1 is what one would expect for a transition state leading from one diastereomer to another via inversion at ruthenium
Phosphino-arene ruthenium complexes containing the phosphorus acid anion {P(=O)(OR)(2)} as P-donor
No full textThe cationic complex [Ru(OTf)(P(OH)Ph-2){Ph2P-(eta (6)-arene)}]OTf,2(2a=6'-diphenylphosphino-1'-naphthyl-eta (6)((1-6))-naphthalene, 2b = 6,6'-dimethoxy-2'-diphenylphosphino-eta (6)((1-6))-biphenyl), is shown to react with water/tert-butyl alcohol/THF mixtures to afford [Ru(P(=O)(OH)(2){Ph2P-(eta (6)-arene)}](2)(OTf)(2), 4. The solid-state structure of a derivative, [Ru{P(=O)(OH)(OMe)}{Ph2P-(naphthyl-eta (6)-naphthalene}](2)(OTf)(2), 6, is reported and found to possess extremely asymmetric eta (6)-arene bonding. Complexes 4 and 6, plus a mononuclear dimethoxy analogue, [Ru(P(=O)-(OMe)(2)(Ph2P-(naphthyl-eta (6)-naphthalene)](OTf), 8, represent the first examples of Ru-compounds that contain the phosphorus acid anion P(=O)(OR) 2 (R = H and/or Me) as an anionic P-donor ligand. PGSE diffusion measurements are shown to be helpful in distinguishing between dinuclear oxygen bridging species and their mononuclear analogues
Structural studies on novel Ru(II)-Binap complexes
No full textThe solid-state structures for two complexes, 7 and 8, are reported. Complex 7 was prepared by treating Ru(OAc)(2)(Binap) with two equivalents of HBArF in toluene solution, and represents only the second solid-state structure of a Binap, complex, in which the Binap is a 6e donor to the Ru(II). The bonding is maintained in solution as shown via C-13 NMR studies. The unusual cation 8, as an SbF6- salt, arises from prolonged reaction of Ru(OAc)(2)(Binap) with wet HBF4 (and, subsequently, added HSbF6) in 1,2-dichloroethane
Emerging Protein Targets for Anticancer Metallodrugs: Inhibition of Thioredoxin Reductase and Cathepsin B by Antitumor Ruthenium (II)-Arene Compounds
No full textA series of ruthenium(II)-arene (RAPTA) compounds were evaluated for their ability to inhibit thioredoxin reductase (either cytosolic or mitochondrial) and cathepsin B, two possible targets for anticancer metallodrugs. In In general, inhibition of the thioredoxin reductases was lower than that of cathepsin B, although selected compounds were excellent inhibitors of both classes of enzymes in comparison to other metal-based drugs. Some initial structure-activity relationships Could be established. On the basis of the obtained data, different mechanisms of binding/inhibition appear to be operative; remarkably the selectivity of the ruthenium compounds toward solid metastatic tumors also correlates to the observed trends. Notably, docking studies of the interactions of representative RAPTA compounds with cathepsin B were performed that provided realistic structures for the resulting protein-metallodrug adducts. Good agreement was generally found between the inhibiting potency of the RAPTA compounds and the computed stability of the corresponding cat B/RAPTA adducts
Polynomial slowdown in space-inhomogeneous branching Brownian motion
No full textWe consider a branching Brownian motion in in which particles independently diffuse as standard Brownian motions and branch at an inhomogeneous rate which depends only on the angle of the particle. We assume that is maximal when , which is the preferred direction for breeding. Furthermore we assume that b(\theta) = 1 - \beta \abs{\theta}^\alpha + O(\theta^2), as , for and \beta>0. We show that if is the maximum distance to the origin at time , then is tight whereand is explicit in terms of the first eigenvalue of a certain operator
Polynomial slowdown in space-inhomogeneous branching Brownian motion
No full textWe consider a branching Brownian motion in in which particles independently diffuse as standard Brownian motions and branch at an inhomogeneous rate which depends only on the angle of the particle. We assume that is maximal when , which is the preferred direction for breeding. Furthermore we assume that b(\theta) = 1 - \beta \abs{\theta}^\alpha + O(\theta^2), as , for and \beta>0. We show that if is the maximum distance to the origin at time , then is tight whereand is explicit in terms of the first eigenvalue of a certain operator
Metal catalysed reactions in ionic liquids
No full textThis book represents first non-edited book on the subject of metal catalysed reactions in ionic liquids and covers the literature from its origins until early 2005. Following a general introduction to the field of biphasic/mutliphasic catalysis, the synthesis, functionalisation and fundamental properties of ionic liquids relevant to catalysis are described. In the ensuing chapters catalysed reactions are discussed according to their type, encompassing hydrogenation, hydroformylation, oxidation, C-C coupling reactions, metathesis, dimerisation, polymerisation and more. Trends, generalisations, advantages and disadvantages of ionic liquids for specific reaction types are discussed. Specific processes such as supported ionic liquid phase catalysis, continuous processes using CO2 extraction and nanoparticle catalysis are covered. The book should be of interest to all those working in catalysis/green chemistry, in particular, to advanced level undergraduate and graduate students and all those researching or contemplating research in bi- or multiphasic catalysis using ionic liquids.LCO
Synthesis of novel room temperature chiral ionic liquids. application as reaction media for the heck arylation of aza-endocyclic acrylates.
No full textNew achiral and chiral RTILs were prepared using novel and/or optimized synthetic routes. These new series of imidazolinium, imidazolium, pyridinium and nicotine-derived ionic liquids were fully characterized including differential scanning calorimetry (DSC) analysis. The performance of these achiral and chiral room temperature ionic liquids (RTILs) was demonstrated by means of the Heck arylation of endocyclic acrylates employing arenediazonium salts and aryl iodides. The Heck arylations performed in the presence of these ionic entities, either as a solvent or as an additive, were effective leading to complete conversion of the substrate and good to excellent yield of the Heck adduct. In spite of the good performances, no asymmetric induction was observed in any of the cases studied. Two new diastereoisomeric NHC-palladium complexes were prepared in good yields from a chiral imidazolium salt and their structure characterized by X-ray diffraction. Overall, the Heck arylations employing arenediazonium tetrafluoroborates in RTILs were more effective than the traditional protocols employing aryl iodides in terms of reactivity and yields
Hydrogenation reactions in ionic liquids: Finding solutions for tomorrow's world
No full textIonic liquids are excellent solvents for conducting biphasic hydrogenation reactions offering many advantages over both related homogeneous processes and biphasic reactions in other alternative solvents. The relevant physicochemical properties of ionic liquids that lend themselves to hydrogenation catalysis are summarised and key hydrogenation reactions/protocols conducted using ionic liquids are discussed. Two new heterogeneous catalyst systems for the hydrogenation of benzene are described. One employs a well known rhodium nanoparticle catalysts, and compared to its use in molecular solvents, reaction rates, ease of use and recyclability, are all improved. The other comprises a new simple platinum-chloroaluminate catalyst system. The preparation of the chloroaluminate ionic liquid on a moderate scale is described together with the chloride salt precursor and the tetrafluoroborate salt. Potentially these ionic liquids (and others) could be prepared by Lonza on a 100 ton scale.LCO
