Asymmetric synthesis of trans-4,5-disubstituted γ-butyrolactones involving a key allylboration step. First access to (-)-nicotlactone B and (-)-galbacin.

An efficient asymmetric synthesis of trans-4,5-disubstituted γ-butyrolactones from aldehydes and enantioenriched γ-carbamate alkenylboronates is reported. The cornerstone of this strategy is the implementation of sequential [3,3]-allyl cyanate rearrangement/allylboration/nucleophilic addition/cyclisation reactions. Diverse γ-butyrolactones such as the flavouring compounds, (+)-trans-whiskey lactone and (+)-trans-cognac lactone, as well as an advanced intermediate towards the first synthesis of natural products, (-)-nicotlactone B and (-)-galbacin, have thus been obtained.

Thermal and near-infrared light induced spin crossover in a mononuclear iron(ii) complex with a tetrathiafulvalene-fused dipyridophenazine ligand.

A mononuclear Fe(ii) complex involving a tetrathiafulvalene-based ligand exhibits thermal spin-crossover (around 143 K) with pronounced hysteresis behaviour (48 K). The chromophoric and π-extended ligand allows Near-Infrared (NIR) sensitization for the light-induced excited spin-state trapping (LIESST) with T(LIESST) = 90 K.

Neutral copper(I) complexes featuring phosphinesulfonate chelates.

The reaction of diphenylphosphinobenzenesulfonic acid with copper(i) oxide resulted in the formation of the new neutral dimeric copper(i) complex {Cu2(DPPBS)2·(MeOH)2}. X-ray diffraction studies revealed that the complex has a dimeric structure and a pyramidal trigonal geometry around the copper atom which contains coordinated methanol molecules at the copper centers. Cleavage of the dimer by reaction with various bipyrimidines enabled the preparation of the corresponding well-defined heterotopic mononuclear [Cu(P^O)(N^N)] and dinuclear {(P^O)Cu(N^N)Cu(P^O)} complexes. X-ray crystal structure determination shows these to have distorted tetrahedral geometries. Their absorption and emission properties were investigated experimentally and photophysical data were also confirmed by DFT and TD-DFT calculations. Owing to the methanol molecules, the neutral crystalline dimer {Cu2(DPPBS)2·(MeOH)2} displays green reversible photoluminescence upon UV irradiation in the solid state with an absolute luminescence quantum yield of 0.51.

Analysis of the electrostatics in Dy(III) single-molecule magnets: the case study of Dy(Murex)3.

A Dy(III)-based single-molecule magnet is reported. Ab initio calculations highlight that molecular symmetry plays a predominant role over site symmetry in determining the shape and orientation of Dy(III) magnetic anisotropy. Moreover the dipolar component of the electrostatic potential created by the surrounding ligands is shown to be the driving force of its magnetic behaviour.

Ethylene oligomerization promoted by chromium complexes bearing pyrrolide-imine-amine/ether tridentate ligands.

Chromium(iii) complexes [CrCl2(L)(THF)] based on monoanionic tridentate ligands [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}; , L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4OPh}] have been prepared. Complexes and were converted into the monomeric acetonitrile adducts [CrCl2(L)(NCMe)] [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}] by reaction with acetonitrile at room temperature. All Cr complexes were characterized by IR spectroscopy, elemental analysis, magnetochemistry for , and by X-ray crystallography for and . Upon activation with methylaluminoxane (MAO), chromium precatalysts and showed good activity in ethylene oligomerization (TOF = 47.0-57.0 × 10(3) (mol ethylene)(mol Cr)(-1) h(-1) at 80 °C), producing mostly oligomers (93.0-95.6 wt% of total products). On the other hand, under identical oligomerization conditions, /MAO behaved as a polymerization catalyst generating predominantly polyethylene (73.0 wt%). However, the catalytic behavior of the precatalyst can be adjusted by varying the MAO-to-Cr ratio. Thus, the use of 500 equiv. causes a dramatic shift from polymerization to ethylene oligomerization, eventually producing mainly lighter α-olefin fractions [α-C4 (68.7 wt%) and α-C6 (19.2 wt%)]. A further increase in the amount of MAO (1000 equiv.) leads to a more balanced distribution of oligomers, with a drastic decrease in the α-C4 and increase in the α-C8 fractions.

Efficient routes towards a series of 5,5'-bithiazolidinylidenes as π-electron acceptors.

Different approaches have been studied in order to prepare efficiently the sulfur rich electron acceptor, DEBTTT. Among the various routes used, the one going through the synthesis of a bicyclic derivative, where the thiazole-2-chalcogenone is fused with a 1,3-dithiole-2-one, leads to the target molecule under milder conditions and better yield. Thus, this approach has been explored for the synthesis of a series of acceptors either by modifying the substituent on the thiazole core or by changing the exocyclic chalcogen atoms. All these sulfur rich electron acceptors exhibit short intra- and intermolecular SS contacts in the solid state. Electrochemical investigations show that the nature of the exocyclic chalcogen atom of the thiazole ring has a significant influence on the accepting ability as a cathodic shift of about 220 mV is observed just by changing sulfur for oxygen. This structural modification enables the tuning of the redox properties.

Dinuclear vs. mononuclear complexes: accelerated, metal-dependent ring-opening polymerization of lactide.

Dinuclear complexes of aluminum and indium with a bis(phenoxy-imine) platform have been synthesized and used in the polymerization of lactide. Kinetic studies demonstrate that the dialuminum precursor provides a more favorable reaction pathway in terms of activation free energy than that of directly related monoaluminum systems. No similar trend is observed with the corresponding diindium-monoindium systems, which is attributed to a dissimilar ROP mechanism.

Antiferromagnetic Ordering of Magnetic Clusters Units in Nb(6)F(15).

We have studied the magnetic cluster compound Nb(6)F(15) which has an odd number of 15 valence electrons per (Nb(6)F(12))(3+) cluster core, as a function of temperature using nuclear magnetic resonance, magnetic susceptibility, electron magnetic resonance and neutron powder diffraction. Nuclear magnetic resonance of the (19)F nuclei shows two lines corresponding to the apical F(a-a) nucleus, and to the inner F(i) nuclei. The temperature dependence of the signal from the F(i) nuclei reveals an antiferromagnetic ordering at T < 5 K, with a hyperfine field of ~2 mT. Magnetic susceptibility exhibits a Curie-Weiss behavior with T(N) ~5 K, and µ(eff) ~1.57 µ(B) close to the expected theoretical value for one unpaired electron (1.73 µ(B)). Electron magnetic resonance linewidth shows a transition at 5 K. Upon cooling from 10 to 1.4 K, the neutron diffraction shows a decrease in the intensity of the low-angle diffuse scattering below Q ~0.27 Å(-1). This decrease is consistent with emergence of magnetic order of large magnetic objects (clusters). This study shows that Nb(6)F(15) is paramagnetic at RT and undergoes a transition to antiferromagnetic order at 5 K. This unique antiferromagnetic ordering results from the interaction between magnetic spins delocalized over each entire (Nb(6)F(12) (i))(3+) cluster core, rather than the common magnetic ordering.

Crystal structure and physical properties of a novel Kondo antiferromagnet: U(3)Ru(4)Al(12).

A novel ternary compound U(3)Ru(4)Al(12) has been identified in the U-Ru-Al ternary diagram. Single-crystal x-ray diffraction indicates a hexagonal Gd(3)Ru(4)Al(12)-type structure for this uranium-based intermetallic. While this structure type usually induces geometrically a spin-glass behaviour, an antiferromagnetic ordering is observed at T(N) = 8.4 K in the present case. The reduced effective magnetic moment of U atoms (µ(eff) = 2.6 µ(B)) can be explained by Kondo-like interactions and crystal field effects that have been identified by a logarithmic temperature dependence of the electrical resistivity, negative values of the magnetoresistivity and particular shape of the Seebeck coefficient.

Down to the quantum limit at the neutral-to-ionic phase transition of (BEDT-TTF)-(ClMe-TCNQ): symmetry analysis and phase diagram.

We report on the neutral-to-ionic (N-I) phase transition in the one-dimensional organic complex (BEDT-TTF)-(ClMeTCNQ). The X-ray studies at room temperature show that the neutral phase of (BEDT-TTF)-(ClMeTCNQ) is already characterized by a polar long-range ordering, at variance with other charge-transfer compounds comprising noncentrosymmetric molecules. From a detailed neutron diffraction study of this complex under high pressure, we present the phase diagram of the N-I transition down to the quantum limit. We discuss the symmetry breaking associated with the transition and the evolution of its first-order character under pressure.

Polynuclear lanthanide hydroxo complexes: new chemical precursors for coordination polymers.

The synthesis of hexanuclear lanthanide hydroxo complexes by controlled hydrolysis led to polymorphic compounds. The hexanuclear entities crystallize in four different ways that depend on the extent of their hydration. The four structures can be described as hexanuclear lanthanide entities with formula [Ln(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](2+). Two additional NO(3)(-) ions intercalate between the hexanuclear entities in order to ensure the electroneutrality of the crystal structure. Some crystallization water molecules fill the intermolecular space. The three first families of compounds (1-3) exhibit crystal structures that have previously been reported. The fourth family of compounds (4) is described here for the first time. Its chemical formula is [Ln(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))(2).2H(2)O (Ln = Gd, Er, and Y). In this paper, the chemical and thermal stabilities of the hexanuclear lanthanide compounds are reported together with the magnetic properties of the Gd(III)-containing species. To use these entities as precursors for new materials, the substitution of the nitrato groups by chloride ions has been studied. Two byproduct compounds have so been obtained: The first (compound 5) is a nitrato/chloride hexanuclear compound of chemical formula [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))Cl.2H(2)O. The second one (compound 6) is a polymeric compound in which the hexanuclear entities are linked by an unexpected and original N(2)O(4) bridge. Its chemical formula is [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(4)(H(2)O)(11)(OH)(ONONO(2))]Cl(3).2H(2)O. Its crystal structure can be described as the juxtaposition of chainlike molecular motifs. To the best of our knowledge, this is the first example of a coordination polymer synthesized from an isolated polylanthanide hydroxo complex.

Bis

The geometry about the Ru atom in the title compound, [Ru(C(9)H(9)N)(2)(C(92)H(108)N(4)O(24))], is approximately tetragonal and the porphyrin ring is nearly planar, while the C-N-R angles [169.3 (3) and 163.9 (3) degrees ] of the isocyanide ligands in the complex are different from the value of 180 degrees expected in the free ligand.