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991.
Gualco P Amgoune A Miqueu K Ladeira S Bourissou D 《Journal of the American Chemical Society》2011,133(12):4257-4259
Over the last decades, our understanding of σ-bond activation at transition metals has progressed considerably from both fundamental and synthetic points of view thanks to the preparation and characterization of a variety of σ complexes. Here we report the synthesis and structural analysis of the first σ complex involving a coinage metal. The copper(I) complex 2 derived from the diphosphine-disilane [Ph(2)P(C(6)H(4))Me(2)Si-SiMe(2)(C(6)H(4))PPh(2)] (1) has been isolated and crystallographically characterized. The coordination of the Si-Si σ bond to copper was thoroughly analyzed by quantum-chemical methods. 相似文献
992.
993.
Fettaka M Issaadi R Moulai-Mostefa N Dez I Le Cerf D Picton L 《Journal of colloid and interface science》2011,357(2):372-378
Thermal behaviors of thermo sensitive hydroxypropyl cellulose (HPC), methyl cellulose (MC) and methyl hydroxypropyl cellulose (MHPC) solutions have been investigated in dilute regime of concentration (C相似文献
994.
Morgan Durand Alexander Stoppa Valérie Molinier Didier Touraud Jean-Marie Aubry 《Journal of solution chemistry》2012,41(3):555-565
Solubility enhancement has been achieved by facilitated hydrotropy for the dimethyl isosorbide (DMI) / benzyl alcohol / water
system. Facilitated hydrotropy has been studied via three different approaches: the solubilization in water of a hydrophobic
dye, the evolution of the surface tension and dynamic light scattering, all as a function of the benzyl alcohol concentration.
The facilitated hydrotropy has been rationalized from the solubilization properties of the system according to the ratio between
the insoluble hydrotrope (here benzyl alcohol, a preservative used in parenteral injections) and the bio-sourced co-solvant
(here the dimethyl isosorbide ether, DMI, a solvent used in pharmaceutical formulation). The presence of self-associated nanostructures
has been detected by dynamic light scattering (DLS). It appears that the cosolvent, DMI, has an antagonistic action: DMI increases
the facilitated hydrotrope (benzyl alcohol) solubility in the aqueous solution (favoring solute solubilization) but simultaneously
decreases the hydrotropic efficiency of benzyl alcohol. 相似文献
995.
Dr. Pierre Brignou Dr. Sophie M. Guillaume Dr. Thierry Roisnel Dr. Didier Bourissou Prof. Jean‐François Carpentier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9360-9370
We describe herein an original approach for the efficient immortal ring‐opening polymerization (iROP) of trimethylene carbonate (TMC) under mild conditions using dual‐catalyst systems combining a discrete cationic metal complex with a tertiary amine. A series of new zinc and magnesium cationic complexes of the type [{NNO}M]+[anion]? ({NNO}?=2,4‐di‐tert‐butyl‐6‐{[(2′‐dimethylaminoethyl)methylamino]methyl}phenolate; M=Zn, [anion]?=[B(C6F5)4]? ( 2 ), [H2N‐ {B(C6F5)3}2]? ( 3 ), and [EtB(C6F5)3]? ( 4 ); M=Mg, [anion]?=[H2N{B(C6F5)3}2]? ( 7 )) have been prepared from the corresponding neutral compounds [{NNO}ZnEt] ( 1 ) and [{NNO}‐ Mg(nBu)] ( 6 ). Compounds 2 – 4 and 7 exist as free ion pairs, as revealed by 1H, 13C, 19F, and 11B NMR spectroscopy in THF solution, and an X‐ray crystallographic analysis of the bis(THF) adduct of compound 7 , 7? (THF)2. The neutral complexes 1 and 6 , in combination with one equivalent or an excess of benzyl alcohol (BnOH), initiate the rapid iROP of TMC, in bulk or in toluene solution, at 45–60 °C (turnover frequency, TOF, up to 25–30 000 mol(TMC)?mol(Zn)?h?1 for 1 and 220–240 000 mol(TMC)?mol(Mg)?h?1 for 6 ), to afford H‐PTMC‐OBn with controlled macromolecular features. ROP reactions mediated by the cationic systems 2 /BnOH and 7 /BnOH proceeded much more slowly (TOF up to 500 and 3 000 mol(TMC)?mol(Zn or Mg)?h?1 at 110 °C) than those based on the parent neutral compounds 1 /BnOH and 6 /BnOH, respectively. Use of original dual organic/organometallic catalyst systems, obtained by adding 0.2–5 equiv of a tertiary amine such as NEt3 to zinc cationic complexes [{NNO}Zn]+[anion]? ( 2 – 4 ), promoted high activities (TOF up to 18 300 mol(TMC)?mol(Zn)?h?1 at 45 °C) giving H‐PTMC‐OBn with good control over the Mn and Mw/Mn values. Variation of the nature of the anion in 2 – 4 did not significantly affect the performance of these catalyst systems. On the other hand, the dual magnesium‐based catalyst system 7 /NEt3 proved to be poorly effective. 相似文献
996.
Dr. Noel Nebra Sonia Ladeira Prof. Laurent Maron Prof. Blanca Martin‐Vaca Dr. Didier Bourissou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(27):8474-8481
In the course of our investigations on polymetallic complexes derived from 1,3‐bis(thiophosphinoyl)indene (Ind(Ph2P?S)2), we observed original fluxional behavior and report herein a joint experimental/computational study of this dynamic process. Starting from the indenylidene chloropalladate species [Pd{Ind(Ph2P?S)2}Cl]? ( 1 ), the new PdII???RhI hetero‐bimetallic pincer complex [PdCl{Ind(Ph2P?S)2}Rh(nbd)] ( 2 ; nbd=2,5‐norbornadiene) was prepared. X‐ray crystallography and DFT calculations substantiate the presence of a d8???d8 interaction. According to multinuclear variable‐temperature NMR spectroscopic experiments, the pendant {Rh(nbd)} fragment of 2 readily shifts in solution at room temperature between the two edges of the SCS tridentate ligand. To assess the role of the pincer‐based polymetallic structure on this fluxional behavior, the related monometallic Rh complex [Rh{IndH(Ph2P?S)2}(nbd)] ( 3 ) was prepared. No evidence for a metal shift was observed in that case, even at high temperature, thus indicating that inplane pincer coordination to the Pd center plays a crucial role. The previously described PdII???IrI bimetallic complex 4 exhibited fluxional behavior in solution, but with a significantly higher activation barrier than 2 . This finding demonstrates the generality of this metal‐shift process and the strong influence of the involved metal centers on the associated activation barrier. DFT calculations were performed to shed light onto the mechanism of such metal‐shift processes and to identify the factors that influence the associated activation barriers. Significantly different pathways were found for bimetallic complexes 2 and 4 on one hand and the monometallic complex 3 on the other hand. The corresponding activation barriers predicted computationally are in very good agreement with the experimental observations. 相似文献
997.
Brignou P Guillaume SM Roisnel T Bourissou D Carpentier JF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(30):9360-9370
We describe herein an original approach for the efficient immortal ring-opening polymerization (iROP) of trimethylene carbonate (TMC) under mild conditions using dual-catalyst systems combining a discrete cationic metal complex with a tertiary amine. A series of new zinc and magnesium cationic complexes of the type [{NNO}M](+) [anion](-) ({NNO}(-) = 2,4-di-tert-butyl-6-{[(2'-dimethylaminoethyl)methylamino]methyl}phenolate; M = Zn, [anion](-) = [B(C(6)F(5))(4)](-) (2), [H(2)N-{B(C(6)F(5))(3)}(2)](-) (3), and [EtB(C(6)F(5))(3)](-) (4); M = Mg, [anion](-) = [H(2)N{B(C(6)F(5))(3)}(2)](-) (7)) have been prepared from the corresponding neutral compounds [{NNO}ZnEt] (1) and [{NNO}-Mg(nBu)] (6). Compounds 2-4 and 7 exist as free ion pairs, as revealed by (1)H, (13)C, (19)F, and (11) B?NMR spectroscopy in THF solution, and an X-ray crystallographic analysis of the bis(THF) adduct of compound 7, 7?(THF)(2). The neutral complexes 1 and 6, in combination with one equivalent or an excess of benzyl alcohol (BnOH), initiate the rapid iROP of TMC, in bulk or in toluene solution, at 45-60?°C (turnover frequency, TOF, up to 25-30,000?mol(TMC)?mol(Zn)?h(-1) for 1 and 220-240,000?mol(TMC)?mol(Mg)?h(-1) for 6), to afford H-PTMC-OBn with controlled macromolecular features. ROP reactions mediated by the cationic systems 2/BnOH and 7/BnOH proceeded much more slowly (TOF up to 500 and 3000?mol(TMC)?mol(Zn or Mg)?h(-1) at 110?°C) than those based on the parent neutral compounds 1/BnOH and 6/BnOH, respectively. Use of original dual organic/organometallic catalyst systems, obtained by adding 0.2-5?equiv of a tertiary amine such as NEt(3) to zinc cationic complexes [{NNO}Zn](+) [anion](-) (2-4), promoted high activities (TOF up to 18,300?mol(TMC)?mol(Zn)?h(-1) at 45?°C) giving H-PTMC-OBn with good control over the M(n) and M(w)/M(n) values. Variation of the nature of the anion in 2-4 did not significantly affect the performance of these catalyst systems. On the other hand, the dual magnesium-based catalyst system 7/NEt(3) proved to be poorly effective. 相似文献
998.
999.
The Friedel-Crafts reaction of (η(4)-tetraphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt with acid chlorides/aluminum chloride resulted exclusively in para-phenyl acylation. Both monoacylated (1.1 equiv of RCOCl/AlCl(3)) and tetraacylated products (>4 equiv of RCOCl/AlCl(3)) were synthesized. Reaction of PhCC(o-RC(6)H(4)) (R = Me, i-Pr) with Na(C(5)H(4)CO(2)Me) and CoCl(PPh(3))(3) gave predominantly (η(4)-1,3-diaryl-2,4-diphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt metallocenes (1,3-[trans] vs 1,2-[cis] selectivity up to 6:1). Conformational control of Friedel-Crafts reactions on the major isomers gave exclusively para-acylation of the unsubstituted phenyl groups. 相似文献
1000.
The C-ON bond homolysis in alkoxyamine 2a can be chemically triggered by the protonation of the 4-pyridylalkyl fragment. The resulting 15-fold increase in k(d) (Chem. Commun. 2011, 47, 4291-4293) was investigated experimentally and theoretically by quaternization of the pyridyl moiety using methylating (MeOTs), acylating (AcCl), and benzylating (PhCH(2)Br) agents as well as by oxidation of the pyridyl moiety into N-oxide and by the formation of a dative bond with BH(3) as a Lewis acid. 相似文献