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61.
Homoleptic Two‐Coordinate Silylamido Complexes of Chromium(I), Manganese(I), and Cobalt(I) 下载免费PDF全文
Dr. C. Gunnar Werncke Dr. Elizaveta Suturina Philip C. Bunting Dr. Laure Vendier Prof. Jeffrey R. Long Prof. Dr. Mihail Atanasov Prof. Dr. Frank Neese Dr. Sylviane Sabo‐Etienne Dr. Sébastien Bontemps 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1668-1674
Anionic two‐coordinate complexes of first‐row transition‐metal(I) centres are rare molecules that are expected to reveal new magnetic properties and reactivity. Recently, we demonstrated that a N(SiMe3)2? ligand set, which is unable to prevent dimerisation or extraneous ligand coordination at the +2 oxidation state of iron, was nonetheless able to stabilise anionic two‐coordinate FeI complexes even in the presence of a Lewis base. We now report analogous CrI and CoI complexes with exclusively this amido ligand and the isolation of a [MnI{N(SiMe3)2}2]22? dimer that features a Mn?Mn bond. Additionally, by increasing the steric hindrance of the ligand set, the two‐coordinate complex [MnI{N(Dipp)(SiMe3)}2]? was isolated (Dipp=2,6‐iPr2‐C6H3). Characterisation of these compounds by using X‐ray crystallography, NMR spectroscopy, and magnetic susceptibility measurements is provided along with ligand‐field analysis based on CASSCF/NEVPT2 ab initio calculations. 相似文献
62.
Grellier M Vendier L Chaudret B Albinati A Rizzato S Mason S Sabo-Etienne S 《Journal of the American Chemical Society》2005,127(50):17592-17593
Treatment of Ru(eta4-C8H12)(eta6-C8H10) with 3 bar H2 in the presence of 2 equiv of tricyclopentylphosphine (PCyp3) in pentane resulted in the isolation of the new bis(dihydrogen) complex RuH2(eta2-H2)2(PCyp3)2 (2), characterized by NMR and single-crystal X-ray and neutron diffraction. The single-crystal neutron diffraction study is the first carried out for a bis(dihydrogen) complex. The coordination geometry around the metal center is a distorted octahedron defined by the two phosphines in a trans configuration (making an angle of 168.9(1) degrees ), two cis dihydrogen ligands, and two hydrides trans to them, defining the equatorial plane. The H-H bond distances (0.825(8) and 0.835(8) A) are characteristic of two "unstretched" dihydrogen ligands. H/D exchange between the Ru-H and the C-D bonds of deuterated benzene is observed within 1 h, leading to the formation of various isotopomers RuHxD6-x(PCyp3)2 (with x = 0-6). 2 is a catalyst precursor for ethylene coupling (20 bar, 293 K) to a functionalized arene (Murai reaction). We found a 90% conversion of acetophenone to 2-ethylacetophenone within 35 min, whereas 10 h was needed in the same conditions using the analogous tricyclohexylphosphine complex, RuH2(eta2-H2)2(PCy3)2, the best catalyst precursor, at room temperature, prior to this work. 相似文献
63.
Immunoaffinity column cleanup with liquid chromatography for determination of aflatoxin M1 in liquid milk: collaborative study 总被引:4,自引:0,他引:4
A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatographic method for determination of aflatoxin M1 in milk at proposed European regulatory limits. The test portion of liquid milk was centrifuged, filtered, and applied to an immunoaffinity column. The column was washed with water, and aflatoxin was eluted with pure acetonitrile. Aflatoxin M1 was separated by reversed-phase liquid chromatography (LC) with fluorescence detection. Frozen liquid milk samples both naturally contaminated with aflatoxin M1 and blank samples for spiking, were sent to 12 collaborators in 12 different European countries. Test portions of samples were spiked at 0.05 ng aflatoxin M1 per mL. After removal of 2 noncompliant sets of results, the mean recovery of aflatoxin M1 was 74%. Based on results for spiked samples (blind pairs at 1 level) and naturally contaminated samples (blind pairs at 3 levels) the relative standard deviation for repeatability (RSDr) ranged from 8 to 18%. The relative standard deviation for reproducibility (RSDR) ranged from 21 to 31%. The method showed acceptable within- and between-laboratory precision data for liquid milk, as evidenced by HORRAT values at the low level of aflatoxin M1 contamination. 相似文献
64.
Montiel-Palma V Lumbierres M Donnadieu B Sabo-Etienne S Chaudret B 《Journal of the American Chemical Society》2002,124(20):5624-5625
Room temperature reaction of the bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1) with excess pinacol borane (HBpin) generates the novel complex RuH[(mu-H)(2)Bpin](sigma-HBpin)(PCy(3))(2) (2) by loss of dihydrogen. Complex 2 was characterized spectroscopically and by X-ray crystallography. It contains two pinacolborane moieties coordinated in a different fashion, one as a dihydroborate (B-H distances : 1.58(3) and 1.47(3) A) and the other as a sigma-borane (B-H distance: 1.35(3) A). In addition, reaction of 1 with one equiv of HBpin yields total conversion to a new complex tentatively formulated as RuH[(mu-H)(2)Bpin](H(2))(PCy(3))(2) (3) on the basis of NMR data. In the presence of excess HBpin, 3 is converted to 2. Furthermore, under an atmosphere of dihydrogen, a C(7)D(8) solution of 2 rapidly converts to 3 and finally regenerates 1 over a much longer period. Thus, complex 3 is an intermediate in the formation of 2 from 1. In these processes the borane is eliminated as HBpin later hydrolyzed to BpinOBpin. Selective hydroboration of ethylene (3 bar) into C(2)H(5)Bpin is achieved using 1 or 2 as catalyst precursors in toluene, whereas in THF, competitive formation of the vinylborane C(2)H(3)Bpin (56% under 20 bar of C(2)H(4)) can be favored. 相似文献
65.
Khaled Essalah Jean-Claude Barthelat Virginia Montiel Sbastien Lachaize Bruno Donnadieu Bruno Chaudret Sylviane Sabo-Etienne 《Journal of organometallic chemistry》2003,680(1-2):182-187
Reaction of the bis(dihydrogen) ruthenium complex RuH2(H2)2(PCy3)2 (1) with an excess of 9-borabicyclononane yields Ru[(μ-H)2BC8H14]2(PCy3) (6) and the phosphine adduct PCy3·HBC8H14. The new complex is characterized by NMR spectroscopy and X-ray diffraction. New X-ray data on 9-BBN dimer, from a measurement at 180 K, are also reported. DFT calculations (B3LYP) on Ru[(μ-H)2BC8H14]2(PMe3) (7), the PMe3 analogue of 6, confirm the ruthenium (II) formulation with two dihydroborate ligands. The data obtained using PH3 or PMe3 as models for PCy3 in PR3·HBC8H14 are also discussed. 相似文献
66.
Two new docetaxel analogues have been prepared starting from 10-deacetylbaccatin III. Both derivatives lack the oxetane D-ring but possess the 4alpha-acetoxy group, which is important for biological activity. The influence of a more or less constrained C-ring was evaluated by adding, or not adding, a double bond in this ring. Both compounds were found to be equally less active than docetaxel in biological assays. [reaction: see text] 相似文献
67.
Angelov B Angelova A Garamus VM Lebas G Lesieur S Ollivon M Funari SS Willumeit R Couvreur P 《Journal of the American Chemical Society》2007,129(44):13474-13479
The structural evolution of a diamond-type bicontinuous lipid cubic phase upon application of thermal and chemical (hydration agent) stimuli is investigated by means of small-angle neutron (SANS) and X-ray scattering (SAXS). The soft-matter cubic architecture responds by dramatic swelling (DLarge cubic structure) upon incorporation of a hydration-enhancing guest component (octyl glucoside) at low and ambient temperatures, the aqueous channel diameter increasing twice to approximately 7 nm. DLarge appears to be built up from an assembly of cubosomic domains, which may coexist with an amphiphilic lamellae domain at low temperatures. The chemical stimulus concentration can be selected as to tune the hydration of the nanochannels in the DLarge phase and its transformation into a DNormal phase at temperatures above the body temperature. Two-dimensional SANS images recorded upon heating scan reveal growth of spontaneously oriented domains of single-crystal cubic nature. Phase separation and squeezing out the guest-hydrating agent from the higher-curvature regions of the amphiphilic bilayer suggest a possible mechanism for the established transformations. The order-order structural transition, cubic DLarge-cubic DNormal, is found to be reversible upon cooling. The obtained results put forward a structure-based concept for release of encapsulated guest molecules from stimuli-responsive and self-regulated cubosomic nanocarriers. 相似文献
68.
Montiel-Palma V Muñoz-Hernández MA Ayed T Barthelat JC Grellier M Vendier L Sabo-Etienne S 《Chemical communications (Cambridge, England)》2007,(38):3963-3965
Reaction of a phosphinobenzylsilane compound with ruthenium complexes leads to C-H and/or Si-H activation. The new complex Ru{eta(2)-H-SiMe2CH(o-C(6)H(4))PPh2}2 (5) was isolated and X-ray, NMR and DFT studies reveal that 5 displays two agostic Si-H interactions and two carbon-metallated bonds. 相似文献
69.
NMR has played a major role in the characterization of dihydrogen complexes and a number of polyhydrides have been reformulated as dihydrogen complexes on the basis of NMR data. If dihydrogen complexes remain the most widely studied class of σ-complexes, silane compounds are also well recognized as an important family of σ-complexes and more recently a few σ-borane compounds have been isolated. One important problem is the discrimination between a σ-formulation and the corresponding hydrido(silyl) or hydrido(boryl) oxidative addition product. In this review we will discuss key literature data on silane and borane complexes to illustrate the benefit gained by using multinuclear NMR spectroscopy to better define the structures and bonding modes. Our goal is also to help the reader to appreciate the limits of the method and to provide valuable insights into the problem of secondary interactions. 相似文献
70.
Angelova A Fajolles C Hocquelet C Djedaïni-Pilard F Lesieur S Bonnet V Perly B Lebas G Mauclaire L 《Journal of colloid and interface science》2008,322(1):304-314
A new class of amphiphilic peptidolipidyl-cyclodextrins is reported. The derivatives are chiral due to the presence of an L-leucine in the spacer arm that links a saccharide moiety and a grafted, saturated hydrocarbon chain. Self-assembly properties of the peptidolipidyl-cyclodextrins are characterized by quasi-elastic light scattering, turbidity and UV-visible absorption measurements. NMR experiments give insight into the intermolecular dipolar interactions as a function of temperature and concentration. N-dodecyl-N alpha-(6 I-amidosuccinyl-6 1-deoxy-cyclomaltoheptaose)-L-leucine (1) is poorly soluble in aqueous media. N-dodecyl-N(alpha)-(6 I-amidosuccinyl-6 I-deoxy-2 I,3 I-di-O-methyl-hexakis-(2 II-VII,3 II-VII,6 II-VII-tri-O-methyl)-cyclomaltoheptaose)-L-leucine (2) is found to be more soluble and self-assembles into stable supramolecular colloidal aggregates with nanometric dimensions above a critical aggregation concentration (CAC). It has a propensity for solubilization of hydrophobic species revealing a micellar-like behavior, which is compared to that of the non-ionic detergent octyl glucoside. On the contrary, compound 1 precipitates in a crystalline phase beyond its water solubility limit, and it does not display any solubilizing capacity. The observed behavior corroborates at the molecular level with the NMR results. 相似文献