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Donor Properties (donor + property)
Selected AbstractsReprogramming of a Malonic N-Heterocyclic Carbene: A Simple Backbone Modification with Dramatic Consequences on the Ligand's Donor PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2010Vincent César Abstract Reaction of N,N, -dimesitylformamidine with dimethylmalonyl dichloride in dichloromethane in the presence of an excess of triethylamine gives the 2-chloro-4,5-dioxohexahydropyrimidine 1. The corresponding diamidocarbene 3 is generated in situ by further deprotonation with KHMDS at ,40 °C and identified by trapping with S8 to give the fully characterized (including X-ray structure) sulfur adduct 4. It also reacts with [RhCl(cod)]2 to yield the NHC complex [RhCl(3)(cod)] (5) (characterized also by X-ray structure). The donor properties of 3 were evaluated against the established IR [,(CO)] scale from [RhCl(3)(CO)2] (6). The average value of ,(CO) = 2045 cm,1 indicates that the diamidocarbene 3 is much less nucleophilic than structurally relevant six-membered NHCs including the anionic diaminocarbenes previously reported in our group. [source] Preparation of kinase-biased compounds in the search for lead inhibitors of kinase targets,MEDICINAL RESEARCH REVIEWS, Issue 3 2005Justine Y.Q. Lai Abstract This work describes the preparation of approximately 13,000 compounds for rapid identification of hits in high-throughput screening (HTS). These compounds were designed as potential serine/threonine or tyrosine kinase inhibitors. The library consists of various scaffolds, e.g., purines, oxindoles, and imidazoles, whereby each core scaffold generally includes the hydrogen bond acceptor/donor properties known to be important for kinase binding. Several of these are based upon literature kinase templates, or adaptations of them to provide novelty. The routes to their preparation are outlined. A variety of automation techniques were used to prepare >500 compounds per scaffold. Where applicable, scavenger resins were employed to remove excess reagents and when necessary, preparative high performance liquid chromatography (HPLC) was used for purification. These compounds were screened against an ,in-house' kinase panel. The success rate in HTS was significantly higher than the corporate compound collection. © 2004 Wiley Periodicals, Inc. [source] Structure, Electrochemistry and Hydroformylation Catalytic Activity of the Bis(pyrazolylborato)rhodium(I) Complexes [RhBp(CO)P] [P = P(NC4H4)3, PPh3, PCy3, P(C6H4OMe-4)3]EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2004Anna M. Trzeciak Abstract Rhodium complexes of formula [RhBp(CO)P] [Bp = bis(pyrazolylborate), P = P(NC4H4)31, PPh32, PCy33, P(C6H4OMe-4)34] have been prepared by exchange of the acetylacetonate (acac,) ligand in [Rh(acac)(CO)P] complexes. The spectroscopic and electrochemical properties as well as X-ray data of [Rh(acac)(CO)P] and [RhBp(CO)P] complexes have been compared with the aim to estimate the relative donor properties of both anionic ligands (acac, and Bp,). The cyclic voltammetric results indicate that the Bp, ligand behaves as a much stronger electron donor than acac, and a value of the Lever EL ligand parameter identical to that of the pyrazolate ligand (,0.24 V vs. NHE for each coordinating arm) is proposed for the bis- and tris(pyrazolyl)borate ligands, whereas P(C6H4OMe-4)3 is also shown to have an identical EL value (0.69 V) to that of P(NC4H4)3. An improved linear relationship between the oxidation potential and the sum of the ligand EL values for square-planar RhI complexes is also obtained and adjusted values for the Lever SM and IM parameters for the RhI/RhII redox couple are given. The trans influence of phosphanes was not observed in crystals of complexes 2 and 3, in contrast to analogous acetylacetonato complexes in which the Rh,O bonds differ by ca. 0.04,0.06 Ĺ. Complexes 1,4 are very attractive precursors for hydroformylation catalysts and yields of aldehydes of 80,87% have been obtained with all complexes without extra phosphane as co-catalyst. During the hydroformylation reaction, however, small amounts of a catalytically inactive [RhBp(CO)2] complex were formed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Syntheses, structures, and supramolecular properties of giant ,-expanded macrocyclic oligothiophenesHETEROATOM CHEMISTRY, Issue 5 2007Masahiko Iyoda Fully conjugated ,-expanded macrocyclic oligothiophenes with 60,-, 90,-, 120,-, 150,-, and 180,-electron systems (1,5) were synthesized using modified McMurry coupling reaction as a key step. Compound 1 was converted into macrocyclic oligo(2,5-thienylene-ethynylene) 6 using bromination-dehydrobromination procedure. X-ray analysis of 1 revealed a unique molecular and packing structure, reflecting a round, planar shape with nanoscale inner cavity. Interestingly, 2 and 3 self-aggregate in the solid state to form nanowires. The structure of fibrous aggregates was established by scanning electron microscopic and atomic force microscopic analyses. Compounds 1,6 exhibit multi-step reversible redox behavior with fairly low first oxidation potentials, reflecting their cyclic conjugation. Doping of 1,3 with iodine gives semiconductors owing to their ,-donor properties and ,,, stacking ability. © 2007 Wiley Periodicals, Inc. 18:460,466, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20337 [source] Synthesis, characterization and hydroformylation activity of 7-azaindolate-bridged dinuclear rhodium(I)phosphines with pendant polar-groupsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2009Chandra Sekhar Vasam Abstract New dinuclear Rh(I),Phosphines of the types [Rh(µ-azi)(CO)(L)]2 (1,3,7) and [Rh(µ-azi)(L)]2 (8) with pendant polar groups, and a chealated mononuclear compound [Rh(azi-H)(CO)(L)] (2) (where azi = 7-azaindolate, L = polar phosphine) were isolated from the reaction of [Rh(µ-Cl)(CO)2]2 with 7-azaindolate followed by some polar mono - and bis -phosphines (L1,L8). A relationship between ,,31P-NMR and ,(CO) values was considered to define the impact of polar-groups on ,-donor properties of the phosphines. These compounds were evaluated as catalyst precursors in the hydroformylation of 1-hexene and 1-dodecene both in mono- and biphasic aqueous organic systems. While the biphasic hydroformylations (water + toluene) gave exclusively the aldehydes, the monophasic one (aqueous ethanol) showed propensity to form both aldehydes and alcohols. The influence of bimetallic cooperative effects, and ,-donor and hydrophilic properties of the phosphines with pendant polar-groups in enhancing the yields and selectivity of hydroformylation products was emphasized. In addition, when strong ,-donor phosphine was used, the ,-acceptor nature of pyridine ring of 7-azaindolate spacer was found to be a considerable factor in facilitating the facile cleavage of CO group during hydroformylation and in supplementing the cooperative effects. Copyright © 2009 John Wiley & Sons, Ltd. [source] Oxidative Electrochemical Switching in Dithienylcyclopentenes, Part 1: Effect of Electronic Perturbation on the Efficiency and Direction of Molecular Switching,CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2005Wesley R. Browne Dr. Abstract The electro- and spectroelectrochemical properties of dithienylhexahydro- and dithienyhexafluorocyclopentenes are reported. The large effect of variation in the central cyclopentene moieties on the redox properties of the dithienylcyclopentenes is in striking contrast to the minor effect on their photochemical properties. The electronic properties of the oxidised compounds in the +1 and +2 oxidation state are reported, and the possibility of electrochemical cyclisation and cycloreversion were explored by UV/Vis spectroelectrochemistry. The efficiency of electrochemical switching is found to be dependent both on the central cyclopentene unit and on the nature of the substituents at C5 of the thienyl rings. For the hexahydrocyclopentene-based compounds oxidative ring closure of the ring-open form is observed, while for the hexafluorocyclopentene-based compounds oxidative ring opening of the ring-closed form is observed. However, the introduction of electroactive groups such as methoxyphenyl allows oxidative ring closure to occur in the hexafluoro compounds. The effect of electrolyte, solvent and temperature on the spectroelectrochemical properties were examined, and the switching process was found to be sensitive to the donor properties of the solvent/electrolyte system employed. In addition, thermally activated reversible isomerisation of the dicationic closed form was observed. The driving force for electrochemical ring opening and closure appears to be dependent on the relative stabilisation of the dicationic ring-open and ring-closed states. This study provides insight into the factors which determine the direction of cyclisation. [source] | ||||||||||