Laboratoire de Chimie Moléculaire et Thioorganique

The development of recording media based on molecular spin‐transition (ST) materials is discussed and applications demonstrated for the first time. The figure shows a compound which exhibits an ST and which is based on Fe II and 1,2,4‐triazole units. The central Fe II ion undergoes an ST at around 210 K which is accompanied by a purple‐white color change. Requirements for future progress are reviewed. magnified image

Abstract Die von Richard F. Heck Ende der sechziger Jahre entdeckte Palladium‐katalysierte Kupplung von Aryl‐ und Alkenylhalogeniden mit Alkenen hat sich nach gelegentlichem Auf‐ und Abschwellen des darauf gerichteten Interesses in den letzten sechs Jahren nachhaltig gemausert. Durch geschickte Auswahl der Substrate und sorgfältige Anpassung der Reaktionsbedingungen gelingen beeindruckende Sequenzen auch unterschiedlicher Reaktionstypen nicht nur nacheinander, sondern vielfach in einem einzigen Verfahrensschritt. Die mittlerweile etablierte Heck‐Reaktion – und eine Reihe mit ihr mechanistisch verwandter Palladium‐katalysierter Umwandlungen an Aren‐, Alken‐ und Alkinderivaten – bietet ungezählte Möglichkeiten, elegant und hochkonvergent komplexe Moleküle aufzubauen; dabei bereiten Sauerstoff‐ und Stickstoffatome (mit Einschränkungen auch Schwefel‐ und Phosphoratome) in den Reaktionen keine Probleme. Das Spektrum der neueren Erfolge beginnt mit den chemo‐ und regioselektiven Einfachkupplungen hochfunktionalisierter Substrate mit unsymmetrisch mehrfach substituierten Reaktionspartnern. Es reicht allerdings viel weiter über Kaskadenreaktionen mit Knüpfung von drei, vier, fünf oder gar acht neuen CC‐Bindungen unter Bildung von oligofunktionellen und oligocyclischen Produkten von beeindruckender Molekülkomplexität bis hin zum enantioselektiven Aufbau von anspruchsvollen Naturstoffmolekülen mit quartären stereogenen Zentren, wie die Beispiele Crinan, Picrotoxinin, Morphin und viele mehr belegen. Zweifellos läßt sich schon heute die Heck‐Reaktion aus dem Methodenarsenal der präparativen Organischen Chemie nicht mehr wegdenken; abzuwarten bleibt lediglich, wann sie Einzug in ein industrielles Produktionsverfahren halten wird.

Environmental concerns have and will continue to have a significant role in determining how chemistry is carried out. Chemists will be challenged to develop new, efficient synthetic processes that have the fewest possible steps leading to a target molecule, the goal being to decrease the amount of waste generated and reduce energy use. Along this path, chemists will need to develop highly selective reactions with atom-economical pathways producing nontoxic byproduct. In this context, C-H bond activation and functionalization is an extremely attractive method. Indeed, for most organic transformations, the presence of a reactive functionality is required. In Total Synthesis, the "protection and deprotection" approach with such reactive groups limits the overall yield of the synthesis, involves the generation of significant chemical waste, costs energy, and in the end is not as green as one would hope. In turn, if a C-H bond functionalization were possible, instead of the use of a prefunctionalized version of the said C-H bond, the number of steps in a synthesis would obviously be reduced. In this case, the C-H bond can be viewed as a dormant functional group that can be activated when necessary during the synthetic strategy. One issue increasing the challenge of such a desired reaction is selectivity. The cleavage of a C-H bond (bond dissociation requires between 85 and 105 kcal/mol) necessitates a high-energy species, which could quickly become a drawback for the control of chemo-, regio-, and stereoselectivity. Transition metal catalysts are useful reagents for surmounting this problem; they can decrease the kinetic barrier of the reaction yet retain control over selectivity. Transition metal complexes also offer important versatility in having distinct pathways that can lead to activation of the C-H bond. An oxidative addition of the metal in the C-H bond, and a base-assisted metal-carbon bond formation in which the base can be coordinated (or not) to the metal complexes are possible. These different C-H bond activation modes provide chemists with several synthetic options. In this Account, we discuss recent discoveries involving the versatile NHC-gold(I) and NHC-copper(I) hydroxide complexes (where NHC is N-heterocyclic carbene) showing interesting Brønsted basic properties for C-H bond activation or C-H bond functionalization purposes. The simple and easy synthesis of these two complexes involves their halide-bearing relatives reacting with simple alkali metal hydroxides. These complexes can react cleanly with organic compounds bearing protons with compatible pK(a) values, producing only water as byproduct. It is a very simple protocol indeed and may be sold as a C-H bond activation, although the less flashy "metalation reaction" also accurately describes the process. The synthesis of these complexes has led us to develop new organometallic chemistry and catalysis involving C-H bond activation (metalation) and subsequent C-H bond functionalization. We further highlight applications with these reactions, in areas such as photoluminescence and biological activities of NHC-gold(I) and NHC-copper(I) complexes.

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A carbon nanotube–Co–MgO composite powder is prepared by reducing a Mg0.9Co0.1O solid solution in H2–CH4 atmosphere. The oxide matrix and part of the Co catalyst are dissolved by acid treatment without damage to the nanotubes. More than 80% of the carbon nanotubes have either one or two walls. The diameters of the nanotubes are in the range 0.5–5 nm. The utilized method may be a real improvement in the low-cost, large-scale synthesis of single- and double-walled carbon nanotubes.

The traditional homogeneous access to aromatic amine derivatives is a nucleophilic aromatic substitution of the corresponding aryl halides. The halogen atom is usually relatively inert to amination reaction unless it is activated by the presence of electron withdrawing groups. Consequently, there has been particular emphasis over the past decade on the synthesis of metal complexes that are active catalysts for the preparation of aromatic amines. This tutorial review focuses on the use of metal-based complexes for the direct amination of aryl halides with ammonia.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTOverview of the Chemistry of 2-ThiazolinesAnnie-Claude Gaumont*, Mihaela Gulea*, and Jocelyne LevillainView Author Information Laboratoire de Chimie Moléculaire et Thioorganique, UMR CNRS 6507, INC3M, FR 3038, ENSICAEN & Université de Caen, 14050 Caen, France* To whom correspondence should be addressed. Phone: 33-231452873/33-231452898. Fax: 33-231452877. E-mail: [email protected], [email protected]Cite this: Chem. Rev. 2009, 109, 3, 1371–1401Publication Date (Web):January 20, 2009Publication History Received26 February 2008Published online20 January 2009Published inissue 11 March 2009https://doi.org/10.1021/cr800189zCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views9008Altmetric-Citations133LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (956 KB) Get e-AlertsSUBJECTS:Alcohols,Cyclization,Ligands,Reaction products,Reagents Get e-Alerts

An innovative concept of activation of electrode materials for Li-ion batteries is proposed through the preparation of carbon-phosphorus (P/C) composites. Carbon-encapsulated phosphorus composites can be successfully prepared via a simple route by the vaporization–condensation of red phosphorus onto mesoporous carbon. Surface area measurements and Raman spectroscopy were used for the characterization of the P/C composites, which were then tested as anode materials in Li-ion batteries showing enhanced electrochemical properties. In contrast to what is observed for pure unsupported phosphorus, Li storage in P/C composite occurs through the reversible formation of Li3P during the discharge process, as clearly evidenced by in situ XRD, leading to capacities greater than 900 mAh g−1 after 20 cycles.

An aminated series: A well-defined iron-catalyzed reductive amination reaction of aldehydes and ketones with aliphatic amines using molecular hydrogen is presented. Under mild conditions, good yields for a broad range of alkyl ketones as well as aldehydes were achieved. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The synthesis, structural characterization, and magnetic properties of a new Prussian blue analogue, the molecule-based ferrimagnet (VIVO)[CrIII(CN)6]2/3·10/3H2O (1) (TC = 115 K), are presented. The crystal structure is determined from the powder X-ray diffraction diagram using the Rietveld method. The system is cubic, space group Fm3m with cell parameter a = 10.490(4) Å. The value of the exchange coupling parameter J (−48 cm-1) between CrIII and VIVO is estimated from the molecular field parameter W, obtained by fitting the |χM-1| = f(T) data in the paramagnetic phase of the compound. The dependence of the TC value is analyzed in relation with the connectivity of the molecular precursor, the stoichiometry of the three-dimensional material, and the nature of the constituting metal ions. The TC value of 1 is compared to that of the high-TC ferrimagnet (315 K) V[Cr(CN)6]0.86·2.8H2O (2); the values of the J parameters are almost the same. This allows us to estimate the TC values for other possible vanadium−chromium ferrimagnets.

The biodegradation of the fuel oil hydrocarbons contained in drilling cuttings was studied in soil microcosms during a 270-day experiment. Concentration and chemical composition of residual hydrocarbons were periodically monitored by quantitative capillary gas chromatography. The decrease in hydrocarbon concentration was logarithmic with time. At the end of the experiment, the fuel oil was 75% degraded. In the saturated fraction, normal and branched alkanes were almost totally eliminated in 16 days ; 22% of the cycloalkanes were not assimilated. The aromatic fraction was 71% degraded ; some polycyclic aromatics were persistent. The resin fraction (10% of the initial weight) was completely refractory to biodegradation. The inorganic part of drilling cuttings had no influence on the biodegradation rates of hydrocarbons. Biogenic hydrocarbons and traces of degradable fuel oil hydrocarbons were protected from microbial activity by the soil and cuttings matrix. Enumerations of total heterotrophic bacteria and hydrocarbon-utilizing bacteria showed a strong stimulation in both populations. Hydrocarbon-degrading strains of bacteria and fungi were isolated and identified at the generic or specific level.

This paper reports the experimental and theoretical investigations of two trigonal bipyramidal Ni(II) complexes, [Ni(Me(6)tren)Cl](ClO(4)) (1) and [Ni(Me(6)tren)Br](Br) (2). High-field, high-frequency electron paramagnetic resonance spectroscopy performed on a single crystal of 1 shows a giant uniaxial magnetic anisotropy with an experimental D(expt) value (energy difference between the M(s) = ± 1 and M(s) = 0 components of the ground spin state S = 1) estimated to be between -120 and -180 cm(-1). The theoretical study shows that, for an ideally trigonal Ni(II) complex, the orbital degeneracy leads to a first-order spin-orbit coupling that results in a splitting of the M(s) = ± 1 and M(s) = 0 components of approximately -600 cm(-1). Despite the Jahn-Teller distortion that removes the ground term degeneracy and reduces the effects of the first-order spin-orbit interaction, the D value remains very large. A good agreement between theoretical and experimental results (theoretical D(theor) between -100 and -200 cm(-1)) is obtained.

Fluoride-based materials have regained interest within the field of Li-ion batteries largely due to the advent of nanosizing which has transformed the insulating insertion compounds into attractive electrode materials. Herein we demonstrate the effectiveness of ionothermal synthesis in the preparation of nanometric LiFePO4F and LiTiPO4F phases with structures isotopic to tavorite LiFePO4(OH) at temperatures of only 260 °C, while temperatures of 600−700 °C are required to obtain coarse powders via the ceramic method. However, the redox-active phases, which are obtained in a high state of division, have lower redox voltages than LiFePO4 despite the presence of fluorine. Additionally, LiTiPO4F shows staircase charge/discharge profiles with Ti2/3+ and Ti3/4+ couples. Though quite unusual in lithium intercalation oxides, a hint of a Li-driven Fe3/4+ transition has been detected in LiFePO4F.

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We consider a quantum system strongly driven by forces that are periodic in time. The theorem concerns the probability $P(e)$ of observing a given energy change $e$ after a number of cycles. If the system is thermostated by a (quantum) thermal bath, $e$ is the total amount of energy transferred to the bath, while for an isolated system $e$ is the increase in energy of the system itself. Then, we show that $P(e)/P(-e)=e^{βe}$, a parameter-free, model-independent relation.

An efficient method has been developed for direct amide bond synthesis between carboxylic acids and amines via (2-(thiophen-2-ylmethyl)phenyl)boronic acid as a highly active bench-stable catalyst. This catalyst was found to be very effective at room temperature for a large range of substrates with slightly higher temperatures required for challenging ones. This methodology can be applied to aliphatic, α-hydroxyl, aromatic, and heteroaromatic acids as well as primary, secondary, heterocyclic, and even functionalized amines. Notably, N-Boc-protected amino acids were successfully coupled in good yields with very little racemization. An example of catalytic dipeptide synthesis is reported.

Following a bottom-up approach to nanomaterials, we present a rational synthetic route from hexacyanometalates [M(CN)(6)](3-) (M=Cr(III), Co(III)) cores to well-defined heptanuclear complexes. By changing the nature of the metallic cations and using a localised orbital model it is possible to control and to tune the ground state spin value. Thus, with M=Cr(III), d(3), S=3/2, three heptanuclear species were built and characterised by mass spectrometry in solution, by single-crystal X-ray diffraction and by powder magnetic susceptibility measurements, [Cr(III)(CNbondM'L(n))(6)](9+) (M'=Cu(II), Ni(II), Mn(II), L(n)=polydentate ligand), showing spin ground states S(G)=9/2 [Cu(II)], with ferromagnetic interactions J(Cr,Cu)=+45 cm(-1), S(G)=15/2 [Ni(II)] and J(Cr,Ni)=+17.3 cm(-1), S(G)=27/2 [Mn(II)], with an antiferromagnetic interaction J(Cr,Mn)=-9 cm(-1), (interaction Hamiltonian H=-J(Cr,M) [S(Cr)Sigma(i)S(M)(i)], i=1-6). With M=Co(III), d(6), S=0, the heptanuclear analogues [Co(III)(CN-M'L(n))(6)](9+) (M'=Cu(II), Ni(II), Mn(II)) were similarly synthesised and studied. They present a singlet ground state and allow us to evaluate the weak antiferromagnetic coupling constant between two next-nearest neighbours M'-Co-M'.

The active site of [Fe-Fe]-hydrogenases is composed of a di-iron complex, where the two metal atoms are bridged together by a putative di(thiomethyl)amine molecule and are also ligated by di-nuclear ligands, namely carbon monoxide and cyanide. Biosynthesis of this metal site is thought to require specific protein machinery coded by the hydE, hydF, and hydG genes. The HydF protein has been cloned from the thermophilic organism Thermotoga maritima, purified, and characterized. The enzyme possesses specific amino acid signatures for GTP binding and is able to hydrolyze GTP. The anaerobically reconstituted TmHydF protein binds a [4Fe-4S] cluster with peculiar EPR characteristics: an S = 1/2 signal presenting a high field shifted g-value together with a S = 3/2 signal, similar to those observed for [4Fe-4S] clusters ligated by only three cysteines. HYSCORE spectroscopy experiments were carried out to determine the nature of the fourth ligand of the cluster, and its exchangeability was demonstrated with the formation of a [4Fe-4S]-imidazole complex.

Since the discovery of the first air stable NHC, this class of compounds has been intensively studied and applied in organometallic chemistry and homogeneous catalysis due to the stability brought to the metal centre. Alternatively, phosphorus based family ligands have already a very long history in these fields of chemistry. It was naturally obvious that the NHC and the phosphorus ligands had to be mixed for the best of organometallic chemistry and homogeneous catalysis. This perspective will highlight the new synthetic routes for NHC bearing a phosphorus moiety such as NHC-phosphenium salt, N-phosphorylated-imidazolium salt, 4-phosphino or 4,5-diphosphino-imidazolium salt and tethered phosphino-imidazolium salt. Then, the recent applications in organometallic chemistry and homogeneous catalysis will be presented.

Abstract Ein Therapieverfahren, das Tumorzellen in Gegenwart gesunder Zellen selektiv zerstört, ist das große Ziel der Onkologen und würde möglicherweise die Rettung für Krebspatienten bedeuten, die an einer der derzeit noch unheilbaren Krebsformen wie Hirntumor und malignes Melanom erkrankt sind. Eine selektive Zellzerstörung ist prinzipiell mit einer Therapie möglich, die auf der Reaktion des 10 B‐Kerns mit einem Neutron geringer kinetischer Energie (thermisches Neutron) beruht. Diese Kernreaktion liefert als Produkte 4 He 2+ ‐ und 7 Li 3+ ‐Io‐nen, etwa 2.4 MeV kinetische Energie sowie etwas γ‐Strahlung. Da die energiereichen und cytotoxischen Produkt‐Ionen im Gewebe nur eine freie Weglänge von etwa einem Zelldurchmesser haben, könnte man den zu zerstörenden Zelltyp dadurch kennzeichnen, daß man nur an oder in ihn 10 B‐Kerne plaziert. In dieser Übersicht beschreibe ich den derzeitigen Stand der chemischen Forschung zu diesem Therapieverfahren (Bor‐Neutroneneinfangtherapie, BNCT), dessen multidisziplinärer Charakter natürlich nicht nur den Einsatz von Chemie, sondern auch den von Biologie, Kernphysik, Medizin und verwandten Spezialgebieten erfordert. Methoden, die entwickelt wurden, um 10 B‐Kerne in Krebszellen zu plazieren, werden in Beziehung gesetzt zu allgemeinen Zellstrukturen und zu den verschiedenen Zellkompartimenten, in denen sich die Borverbindungen befinden können. Es werden sowohl die Methoden zur Synthese von borhaltigen Biomolekülen und Medikamenten als auch repräsentative Befunde zu deren Effektivität bei der gezielten Anreicherung in Krebszellen vorgestellt. Die Aussichten für eine wirkungsvolle BNCT sind dank rascher Entwicklung z. B. auf den Gebieten bioorganische Chemie, Mikrobiologie, Immunologie und Kernchemie sehr gut. Es konnten effektive Borliefersysteme identifiziert werden, die durch die Zusammenarbeit von Chemie und Biologie sicherlich noch weiter verbessert werden können.