Angeles Monge

Synthesis, Characterization, Molecular Structure and Theoretical Studies of Axially Fluoro-Substituted Subazaporphyrins

A new and general synthetic method for the preparation of fluoro-substituted subazaporphyrins is reported that involves the treatment of the corresponding chloro- or aryloxy-substituted subazaporphyrins (SubAPs) with BF(3).OEt(2). The strategy has been applied to both subphthalocyanines (SubPcs) and subporphyrazines (SubPzs). The yields were high for the latter, although low yields were obtained for the benzo derivatives. In contrast to the corresponding chloro derivatives, fluorosubazaporphyrins are quite robust towards hydrolysis. All of the new compounds were characterized by several spectroscopic techniques, which included (1)H, (13)C, (19)F, (15)N, and (11)B NMR spectroscopy, IR spectroscopy, UV/Vis spectrophotometry, and mass spectrometry (both high and low resolution). In addition, DFT calculations provided theoretical NMR spectroscopy values that are in good agreement with the experimental ones. The high dipole moments exhibited by the fluorosubazaporphyrins as a result of the presence of a fluorine atom in an axial position are responsible for the spontaneous and singular supramolecular aggregation of the macrocycles in the crystalline state. The molecular and crystal structures of two one-dimensional fluorine SubAPs, namely, a SubPc and a SubPz, are discussed. Molecules of the same class stack in alternating configurations along the c axis, which gives rise to columns that contain large numbers of monomers. SubPz 3 c forms aggregates with the macrocycles arranged in a parallel fashion with the B-F bonds perfectly aligned within a column, whereas with SubPc 3 b the neighboring columns cause a commensurate sinusoidal distortion along the columns in the c direction, which prevents the alignment of the B-F bonds. However, the most remarkable feature, common to both crystalline architectures, is the extremely short and unusual intermolecular F...N distances of the contiguous molecules, which are shorter than the sum of the corresponding van der Waals radii. Theoretical calculations have shown that these short distances can be explained by the existence of a cooperativity effect as the number of monomers included in the cluster increases.

One teflon®-like channelled nanoporous polymer with a chiral and new uninodal 4-connected net: sorption and catalytic properties

Zn(C17H8F6O4) is the first example of a fluoro-lined nanotube organo-inorganic 3D polymeric chiral structure, which possesses two different types of isolated channels, one of them being laid out with a double spiral of CF3-groups from the ligand molecule; the structure is a new uninodal 4-connected net that only exists when bent ligands connect the centres, and the compound exhibits selective sorption and catalytic chiral recognition properties.

C−H Bond Activation of Benzene and Cyclic Ethers by TpIrIII Species

An unusual Fischer carbene derivative that, in addition, contains an alkyl and a hydride ligand is obtained by C−H bond activation of THF by the hydride–vinyl species [TpMe2IrH(CHCH2) (C2H4)]. This complex is also capable of activating the C−H bonds of benzene to give remarkably stable IrIII–N2 complexes (see illustration).

Dynamic calcium metal-organic framework acts as a selective organic solvent sponge

Herein, we present a Ca-based metal-organic framework named AEPF-1, which is an active and selective catalyst in olefin hydrogenation reactions. AEPF-1 exhibits a phase transition upon desorption of guest molecules. This structural transformation takes place by a crystal to crystal transformation accompanied by the loss of single-crystal integrity. Powder diffraction methods and computational studies were applied to determine the structure of the guest-free phase. This work also presents data on the exceptional adsorption behavior of this material, which is shown to be capable of separating polar from nonpolar organic solvents, and is a good candidate for selective solvent adsorption under mild conditions.

Heterogeneous Catalysis with Alkaline-Earth Metal-Based MOFs: A Green Calcium Catalyst

A new class of hydrogenation catalysts is required to develop cheaper and environmentally friendly alternatives, in order to avoid the loss of the huge quantities of precious metals, such as Pd, Pt, Rh, Ir, Re, which are widely used to perform traditional heterogeneous hydrogenation for the needs of pharmaceutical, petrochemical, food, soap and detergent, or plasticizer industries. Soluble rhodium and iridium complexes, such as Wilkinson’s and Crabtree’s catalysts, are elegant examples of homogeneous catalysts for these reactions. However, the complicated recovering and recycling processes of homogeneous catalysts have prevented many of them from being commercialized. In this context, metal–organic frameworks (MOFs) can be expected to provide interesting alternatives. These materials are known to possess the capability for several important functionalities, including gas storage, catalysis, and optical properties. Usually, transition metals or rare earths are used to synthesize MOF materials, yet, in spite of the similarities between rare-earth and alkaline-earth complexes, the use of the latter to build MOFs has been much less studied. However, the high Lewis acidity of the alkalineearth metal ions can provide catalysts with very active sites for alkene hydrogenation; strontium and calcium complexes have recently been used as homogeneous catalysts, both for hydrogenation and polymerization of alkenes. Taking into account these considerations, we present herein the synthesis and studies of the properties of a new MOF based on calcium, one of the most abundant and cheap elements. This environmentally friendly material could provide an alternative to traditional precious metal-based hydrogenation catalysts, owing to its low cost, easy fabrication, thermal stability, and robust framework. Previously, we have reported heterogeneous catalysts based on Ln, In, and Zn cations with 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb) as a ligand. [8] MOFs of H2hfipbb with transition metals such as Cu and Co have also been studied. Solvothermal reaction of Ca(CH3CO2)2·H2O and H2hfipbb in a water/acetone mixture resulted in the formation of a new MOF with the formula [Ca(hfipbb)(H2hfipbb)0.5(H2O)]·0.7 C3H6O, AEPF-1 (AEPF = alkaline earth polymeric framework) in approximately 70 % yield. In AEPF-1 calcium atoms are heptacoordinated to form monocapped octahedra, whose vertices are occupied by five oxygen atoms from completely deprotonated hfipbb ligands, one from a protonated H2hfipbb ligand, and one water molecule (Figure 1). For every Ca + cation there is one

Formation in solution, synthesis and crystal structure of μ-oxalatobis[bis(2-pyridylcarbonyl)amido] dicopper(II)

Abstract The compound μ-oxalatobis[bis(2-pyridylcarbonyl)amido] dicopper(II), [Cu 2 {(NCsH 5 CO) 2 N} 2 - (C 2 O 4 )] was synthesized and characterized by spectroscopy, EPR and diffraction methods. It crystallizes in the triclinic space group P 1 with cell constants: a =7.6793(6), b =9.238(2), c =10.007(2) A, α=83.80(1), β=68.37(1) and γ=69.44(1)°; V =617.7(3) A 3 , D (calc., Z =2)=1.80 g cm −3 , M r =667.6, F (000)=336, λ, (Mo Kα)=0.71069 A, μ (Mo Kα)=17.895 cm −1 and T =295 K. A total of 3587 data were collected over the range of 1 ⩽ θ ⩽ 30°; of these, 2391 (independent and with I⩾2σ( I )) were used in the structural analysis. The final R and R w residuals were 0.049 and 0.053, respectively. The structure consists of neutral centrosymmetrical binuclear entities in which C 2 O 4 2− acts in an asymmetrically bis-bidentate fashion. Each copper atom is in a square-pyramidal environment with the three nitrogen atoms of bis(2-pyridylcarbonyl)- amido anion and an oxygen atom of oxalate in the basal plane and another oxygen atom of oxalate occupying the apical position. The stability constants of the oxalato complexes of bis(2-pyridylcarbonyl)amidocopper( II ) have been determined in dimethyl sulphoxide solution: log β 111 =12.22 ± 0.05, log β 110 =7.0 ± 0.1 and logβ 210 =10.25 ± 0.1 at 25 °C and 0.1 mol dm −3 tetra-n-butylammonium perchlorate. Coordination modes of oxalate for this system are compared in DMSO and water in the light of thermodynamic and structural parameters

Self-Assembly of C3-Symmetrical Hexaaryltriindoles Driven by Solvophobic and CH―π Interactions

The synthesis and aggregation properties of a series of differently substituted star-shaped hexaaryltriindoles both in solution and in the solid state are being reported. While these molecules do not show any significant intermolecular aggregation in CDCl(3), it has been possible to induce aggregation by increasing the polarity of the solvent and therefore facilitating the occurrence of solvophobic forces. A study of the influence of the electronic character of peripheral substituents on the self-association behavior in solution has shown that increasing the electron-donor character of the substituents facilitates self-association while derivatives substituted with electron-acceptor substituents do not self-assemble. The electronic nature of the substituents also has an influence in the geometry of the stacking of these derivatives observed in the solid state. While unsubstituted hexaphenyl triindole self-assemble in a staggered face-to-face arrangement, attaching six cyano functional groups results in an offset stacking. The influence of the substituents in the strength and geometry of the stacking tendency contrasts with the trend expected for an aggregation induced solely by pi-pi interactions, but can be explained considering an important contribution of multiple cooperative CH-pi interactions.

Cyclometallated complexes of Pd(II) and Pt(II) with 2-phenylimidazoline

Abstract Cyclometallated complexes of Pd(II) and Pt(II) with 2-phenylimidazoline were synthesized. The complexes were characterized by 1H and 13C NMR spectroscopy, involving the use of COSY-45, HMQC and HMBC techniques, which allow unambiguous assignment of the NMR parameters. An X-ray diffraction study of [Pd(C6H4−C3H5N2)(μ-OAc)]2 confirmed that cyclometallation of the 2-phenylimidazoline ligand had occurred.

3-[4-Phenoxyphenyl]pyrazole (Hpzpp) and 3-[4-butoxyphenyl]pyrazole (Hpzbp) in rhodium chemistry crystal structures of 3-[4-phenoxyphenyl]pyrazole, [Rh(μ−pzpp)(COD)]2⋅12CH2C12 and [Rh(μ-pzbp)(COD)]2

Abstract The novel pyrazoles containing 3-[4-phenoxyphenyl] (pp) and 3-[4-butoxyphenyl] (bp) substituents, Hpzpp and Hpzbp, have been synthetized and characterized, and the crystalline structure of 3-[4-phenoxiphenyl]pyrazole (Hpzpp) is also reported. Rh(I) compounds [Rh(Cl)(HpzR)(LL)] and [Rh(μ-pzR)(LL)]2 (LL = NBD, COD, 2CO; R = pp, bp) have been prepared in order to explore the influence of the alkoxy- or aryloxyphenyl substituents on the pyrazol ring of some features such as the presence of dynamic processes or the preference of determined isomers in the complexes. The molecular structures of complexes [Rh(Cl)(HpzR)(LL)] and [Rh(μ-pzR)(LL)]2 (LL = NBD, COD, 2CO; R = pp, bp) have been studied by IR and 1H and 13C NMR spectroscopies. 1H NMR spectra of compounds [Rh(Cl)(HpzR)(LL)] (LL = NBD, COD, 2CO; R = pp, bp) indicate that the presence of a metallotropic equilibrium only depends on the steric characteristics of the ancillary ligands. On the other hand, complexes [Rh(μ-pzR)(CO)2]2 (R = pp, bp) are formed as a mixture of the head-to-head (H-H) and head-to-tail (H-T) configurational isomers. By contrast, [Rh(μ-pzR)(LL)]2 (LL = NBD, COD; R = pp, bp) have been obtained as only one isomer in both the solid state and the solution. The crystalline structures of complexes [ Rh ( μ − pz pp ) ( COD ) ] 2 ⋅ 1 2 CH 2 C1 2 and [Rh(μ-pzbp)(COD)]2 have been solved, showing the presence of the H-T configurational isomer in both cases. The 1H NMR spectra of [Rh(μ-pzR)(LL)]2 (LL = NBD, COD, 2CO; R = pp, bp) show that the ortho protons of the C6H4 group of the substituents on the pyrazol ring are considerably deshielded. Furthermore, the X-ray structures of [ Rh ( μ − pz pp ) ( COD ) ] 2 ⋅ 1 2 CH 2 C1 2 and [Rh(μ-pzbp)(COD)]2 complexes show an Rh-H(ortho) distance of ca. 2.7 A, characteristic of a weak preagostic interaction.

Reaction of diruthenium(II,III) acetate with triphenylphosphine

Abstract The reaction of [Ru2(μ-O2CCH3)4(thf)2]BF4 with triphenylphosphine in thf or toluene is described. In this reaction, a yellow compound of formula Ru(O2CCH3)2 (PPh3)·CH3C6H5 (1), and a violet, diamagnetic oxo-bridged compound, formulated as Ru2(μ-O)(μ-O2CCH3)2(O2CCH3)2(PPh3)2 (2) are obtained. The compounds have been characterized by elemental analysis, magnetic susceptibility measurements and spectroscopic techniques. The structure of 2 has been determined by X-ray crystallography. Two pseudo-octahedral ruthenium(III) atoms are bridged by an oxo and two acetate ligands. The hexacoordination of each ruthenium atom is completed with a bidentate acetate and a triphenylphosphine ligand. Some spectroscopic evidence for the formation of a tetranuclear intermediate compound is also presented.