Synthesis and Structural Characterization of a Series of One-Dimensional Heteronuclear Dirhodium-Silver Coordination Polymers.

Herein, we describe the preparation of heteronuclear dirhodium-silver complexes by reaction between molecular Rh(II)-Rh(II) compounds [Rh2(µ-O2CR)4L2] (R = Me, Ph (1), CH2OEt (2); L = solvent molecules) with paddlewheel structure and PPh4[Ag(CN)2]. One-dimensional coordination polymers of (PPh4)n[Rh2(µ-O2CR)4Ag(CN)2]n (R = Me (3), Ph (4), CH2OEt (5)) formula have been obtained by replacement of the two labile molecules in the axial positions of the paddlewheel structures by a [Ag(CN)2]- bridging unit. The crystal structures of 3⁻5 display a similar arrangement, having anionic chains with a wavy structure and bulky (PPh4)⁺ cations placed between the chains. The presence of the (PPh4)⁺ cations hinders the existence of intermolecular Ag-Ag interactions although several C-H····π interactions have been observed. A similar reaction between [Rh2(µ-O2CCMe3)4(HO2CCMe3)2] and PPh4[Ag(CN)2] led to the molecular compound (PPh4)2{Rh2(µ-O2CCMe3)4[Ag(CN)2]2} (6) by replacement of the axial HO2CCMe3 ligands by two [Ag(CN)2]- units. The trimethylacetate ligand increases the solubility of the complex during the crystallization favouring the formation of discrete heteronuclear species.

Crystal structure of (1Z,4Z)-2,4-dimethyl-3H-benzo[b][1,4]diazepine.

The title compound, C11H12N2, is not planar due to the folding of the seven-membered ring. In the crystal, mol-ecules are packed opposite each other to minimize the electronic repulsion but the long inter-molecular distances indicate that no directional contacts are found.

Pyrrole-pyridine and pyrrole-naphthyridine hosts for anion recognition.

The association constants of the complexes formed by two hosts containing pyrrole, amide and azine (pyridine and 1,8-naphthyridine) groups and six guests, all monoanions (Cl-, CH3CO2-, NO3-, H2PO4-, BF4-, PF6-), have been determined using NMR titrations. The X-ray crystal structure of the host N2,N5-bis(6-methylpyridin-2-yl)-3,4-diphenyl-1H-pyrrole- 2,5-dicarboxamide (1) has been solved (P21/c monoclinic space group). B3LYP/6-31G(d,p) and calculations were carried out in an attempt to rationalize the trends observed in the experimental association constants.

Gallium-catalyzed domino arylation/oxycyclization of allenes with phenols.

The synthesis of dihydrobenzofuran-appended oxindoles has been accomplished taking advantage of an unprecedented reaction between allenols and phenols under metal catalysis.

Investigation of the Passerini and Ugi reactions in ß-lactam aldehydes. Synthetic applications.

Passerini (P-3CR) and Ugi (U-4CR) reactions were investigated in 4-oxoazetidine-2-carboxaldehydes, affording the corresponding Passerini and Ugi adducts with moderate diastereoselectivity in high yields. Fortunately, the obtained mixtures of isomers syn/anti were separated in most cases. The scope of both IMCRs has been studied using a variety of isocyanides, carboxylic acids and amines. Ugi adducts were used for the preparation of unusual 2-azetidinones fused to medium-sized rings via RCM. In addition, ß-lactam-diketopiperazine hybrids have also been prepared from the corresponding Ugi adducts.

Three-step metal-promoted allene-based preparation of bis(heterocyclic) cyclophanes from carbonyl compounds.

A straightforward metal-mediated method for the synthesis of bis(dihydrofuryl) cyclophane scaffolds from carbonyl compounds has been developed. The combination of the dihydrofuran moiety with different heterocycles such as ß-lactams and sugars allows high levels of skeletal diversity. The process comprises indium-promoted one-pot carbonyl bis(allenylation) and gold- or palladium-catalyzed double cyclization in the resulting bis(allenols), followed by selective ruthenium-catalyzed macrocyclization. In some cases, the method has been successfully applied to the synthesis of the challenging Z-isomers. The E- versus Z-stereochemistry of the metathesis-formed double bonds could not be assigned taking into consideration the usual coupling constants criteria, but a diagnostic based on the chemical shifts of the two olefinic protons located at the macrocyclic double bond was established.

A gold-catalysed imine-propargylamine cascade sequence: synthesis of 3-substituted-2,5-dimethylpyrazines and the reaction mechanism.

The gold-catalysed coupling reaction between propargylamine-derived imines and propargylamine exclusively afforded pyrazines. Besides, in order to understand the mechanism of this sequence, deuterium labeling and computational studies have been performed.

Structural, magnetic and electrical properties of one-dimensional tetraamidatodiruthenium compounds.

The first bromo and iodo tetraamidatodiruthenium compounds of the type [Ru2X(µ-NHOCC6H4-R)4]n [X = Br, R = o-Me (1), m-Me (2), p-Me (3); X = I, R = o-Me (4), m-Me (5), p-Me (6)] have been prepared using solvothermal or microwave activation procedures. In these reactions ethanol or methanol as solvents have been used to make the synthesis procedures more environment-friendly. Solvothermal synthesis has allowed us to isolate single crystals of these extremely insoluble compounds and the crystal structures of all of them have been determined using single crystal X-ray diffraction. The change of the bridging halide ligand permits us to discuss the properties of these complexes on the basis of their structure. Complex 1 shows a Ru-Br-Ru angle of 180.0° whereas in complexes 2-6 the Ru-X-Ru angle varies from 110.16(2) to 115.39(4)°. In all compounds the ruthenium atom has a cis-RuN2O2 environment except in compound 1 that shows a positional disorder of N and O atoms. The bromide complex 1 shows a linear arrangement of the paddlewheel units in the resulting 1D coordination polymer. The fit of the magnetic data indicates that these compounds have non-negligible values of zero-field splitting with D values ranging from 41.10 to 60.10 cm(-1) and antiferromagnetic coupling constants from 0.00 to -4.13 cm(-1). Compound 1 is the first linear paddlewheel diruthenium compound that does not show a maximum in the representation of the magnetic susceptibility towards temperature. The electrical conductivity measurements in the temperature range 300-400 K of compounds 1, 4 and [Ru2Cl(µ-NHOCC6H4-o-Me)4]n (7) show that these compounds present semiconducting behaviours with conductivity values at 400 K in the range 0.3-3.0 × 10(-8) S cm(-1) for the Cl derivative (7), 7-18 × 10(-8) S cm(-1) for the Br derivative (1) and 27-68 × 10(-8) S cm(-1) for the I derivative (4) with average values of 1.4 × 10(-8), 13 × 10(-8) and 47 × 10(-8) S cm(-1), respectively.

Synthesis of fused-ß-lactams through selective gold-catalyzed oxycyclization of dioxolane-tethered enynes.

The gold-catalyzed preparation of 2-azetidinone-fused oxacycles was accomplished from ß-lactam-linked enynes through heterocyclization reaction taking advantage of the acetonide pendant group. While the synthesis of fused tetrahydrofuran-ß-lactams from 1,3-enynes could be considered as an unusual metal-catalyzed cyclization of enynols, α-alkoxy dioxolane-tethered 1,3-enynes exclusively undergo bis-oxycyclization to afford tricyclic bridged acetals.

Iodine recycling via 1,3-migration in iodoindoles under metal catalysis.

3-Substituted (indol-2-yl)-α-allenols show divergent patterns of reactivity under metal catalysis. An unprecedented intramolecular 1,3-iodine migration is described.

The structure of azines derived from C-formyl-1H-imidazoles in solution and in the solid state: tautomerism, configurational and conformational studies.

The structures of three azines derived from 2-formylimidazole, 4(5)-formylimidazole, and 4(5)-formyl-5(4)-methylimidazole have been determined in solution and in the solid state. Density Functional Theory (DFT) Polarizable Continuum Model (PCM) calculations (geometries, energies, and chemical shifts), NMR [solution and cross polarization magic-angle spinning (CPMAS)], and X-ray crystallography [azine of 4(5)-formylimidazole] have been used. The configuration around the central C = N bonds has been determined and some insights about prototropic tautomerism and conformation have been gained.

Silver-pyrazole complexes as hybrid multifunctional materials with metallomesogenic and photoluminescent behaviour.

New pyridine-functionalised pyrazole compounds [Hpz(R(n)py)] (R(n) = C(6)H(4)OC(n)H(2n+1); n = 12, 14, 16, 18; 1-4) and their corresponding silver complexes [Ag(Hpz(R(n)py))(2)][A] ([A] = NO(3)(-), BF(4)(-); ) have been synthesised and characterised. All of them, with the exception of 1, are liquid crystal materials exhibiting monotropic or enantiotropic SmA mesophases, in contrast to the non-mesomorphic related R(n)-monosubstituted compounds. Because the molecular shape is a factor determinant in the organisation of molecules in the liquid crystal phase, we were interested in solving the crystal structure of representative examples of the mentioned compounds, such as 1 and 6. So, the X-ray crystal structure of [Hpz(R(12)py)] 1 shows the presence of dimeric units through N-H···N hydrogen bonds, which conform to an elongated molecular shape containing a double chain length. On the other hand, the structure of [Ag(Hpz(R(14)py))(2)][NO(3)] 6 also evidenced Ag-Ag bonded dimers from 'U'-shaped cationic entities. These dimers exhibit four chains, two by two alternated, so giving rise to a longer molecular length. Of particular interest was to observe that in both structures, the dimers are layer-like packed, their lamellar structures being related to that of the mesophases found in both kinds of compounds. Furthermore, the analysis of the optical data of the compounds 2 and 4 and the silver compounds 5, 6, 9 and 10 as representative examples pointed out their luminescent behaviour as well as their good ability to act as fluorescent probes for Zn(2+), Cu(2+) and Ag(+). An increase in the fluorescence quantum yields is observed in the final complexes produced in the titrations, this fact being specially notable when 9 was used as the starting compound.

Regio- and diastereoselective synthesis of ß-lactam-triazole hybrids via Passerini/CuAAC sequence.

Passerini (P-3CR) and Passerini-Smiles reactions were investigated in azetidine-2,3-diones, affording the corresponding 3,3-disubstituted-ß-lactams with complete diastereoselectivity in high yields. The study has been carried out using different isocyanides, carboxylic acids, and phenols showing the scope of both reactions. In addition, the regioselective synthesis of highly functionalized ß-lactam-triazole hybrids has been developed via a Passerini/CuAAC sequence. Interestingly, the use of dialkynes/diazides or trialkynes/triazides as linkers in the CuAAC step has allowed the synthesis of C(2) and C(3) symmetric ß-lactam-triazole hybrids, respectively.

Structure and properties of one-dimensional heterobimetallic polymers containing dicyanoaurate and dirhodium(II) fragments.

The synthesis and characterization of compound [Rh(2)(O(2)CEt)(4)(H(2)O)(2)] (1) and one-dimensional heterobimetallic polymers K(n){Rh(2)(O(2)CEt)(4)[Au(CN)(2)]}(n) (2) and K(n){Rh(2)(O(2)CMe)(4)[Au(CN)(2)]}(n)·4nH(2)O (3), constructed from dirhodiumtetracarboxylato units, [Rh(2)(O(2)CR)(4)](+), and dicyanoaurate, [Au(CN)(2)](-), fragments are described. In both compounds 2 and 3 the resulting polymeric chains are nonlinear and have in common similar structural parameters, although the solid state supramolecular arrangement is very different. These structural differences explain the fact that complex 2 displays aurophilic interactions while this type of interactions are absent in complex 3. As a result, compound 2 shows rich blue luminescent properties whereas compound 3 is not luminescent. The electrical conductivity in solid state of compounds 2 and 3 is also studied.

Ring enlargement versus selenoetherification on the reaction of allenyl oxindoles with selenenylating reagents.

Lactam-tethered allenols, readily prepared from α-oxolactams, were used as starting materials for divergent reactivity with selenenylating reagents. Either oxycyclization (spirocyclic selenolactams) or ring expansion (selenoquinolones) can be achieved through the choice of both reagents and substrates. The biological activity of some of the synthesized heterocycles has additionally been evaluated in four human cancer cell lines.

Reactions of hydridoirida-ß-diketones with amines or with 2-aminopyridines: formation of hydridoirida-ß-ketoimines, PCN terdentate ligands, and acyl decarbonylation.

The hydridoirida-ß-diketone [IrHCl{(PPh(2)(o-C(6)H(4)CO))(2)H}] (1) reacts with benzylamine (C(6)H(5)CH(2)NH(2)) to give the hydridoirida-ß-ketoimine [IrHCl{(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNCH(2)C(6)H(5)))H}] (2), stabilized by an intramolecular hydrogen bond. 2 reacts with water to undergo hydrolysis and amine coordination giving hydridodiacylamino [IrH(PPh(2)(o-C(6)H(4)CO))(2)(C(6)H(5)CH(2)NH(2))] (3). Cyclohexylamine or dimethylamine lead to hydridodiacylamino [IrH(PPh(2)(o-C(6)H(4)CO))(2)L] (4-5). In chlorinated solvents hydridodiacylamino complexes undergo exchange of hydride by chloride to afford [IrCl(PPh(2)(o-C(6)H(4)CO))(2)L] (6-9). The reaction of 1 with hydrazine (H(2)NNH(2)) gives hydridoirida-ß-ketoimine [IrHCl{(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CNNH(2)))H}] (10), fluxional in solution with values for ΔH(‡) of 2.5 ± 0.3 kcal mol(-1) and for ΔS(‡) of -32.9 ± 3 eu. A hydrolysis/imination sequence can be responsible for fluxionality. 2-Aminopyridines (RHNC(5)H(3)R'N) react with 1 to afford cis-[IrCl(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CHNRC(5)H(3)R'N))] (R = R' = H (11), R = CH(3), R' = H (12), R = H, R' = CH(3) (13)) containing new terdentate PCN ligands in a facial disposition and cis phosphorus atoms as kinetic products. The formation of 11-13 requires imination of the hydroxycarbene moiety of 1, coordination of the nitrogen atom of pyridine to iridium, and iridium to carbon hydrogen transfer. In refluxing methanol, complexes 11-13 isomerize to afford the thermodynamic products 14-16 with trans phosphorus atoms. Chloride abstraction from complexes [IrCl(PPh(2)(o-C(6)H(4)CO))(PPh(2)(o-C(6)H(4)CHNRC(5)H(4)N))] (R = H or CH(3)) leads to decarbonylation of the acylphosphine chelating group to afford cationic complexes [Ir(CO)(PPh(2)(o-C(6)H(4)))(PPh(2)(o-C(6)H(4)CHNRC(5)H(4)N))]A, 17 (R = H, A = ClO(4)) and 18 (R = CH(3), A = BF(4)) as a cis/trans = 4:1 mixture of isomers. Single crystal X-ray diffraction analysis was performed on 6, 9, 13, and 14.

Synthetic hosts for molecular recognition of ureas.

Four hosts (7-10) containing 2,6-bisamidopyridine- and 2,5-bisamidopyrrole-bearing pyridyl or 1,8-naphthyridyl groups have been prepared and their structures studied by a combination of multinuclear NMR spectroscopy and X-ray crystallography. Their behavior in molecular recognition of urea derivatives, including (+)-biotin methyl ester, has been approached by molecular modeling (Monte Carlo conformational search, AMBER force field). The minimum energy values for the complexes are correlated with the experimental binding energies determined by means of (1)H NMR titrations.

Trapping intermediates in an [8 + 2] cycloaddition reaction with the help of DFT calculations.

DFT calculations predict that the [8 + 2] cycloaddition reaction between ketenes and 8-azaheptafulvenes occurs stepwise through antiaromatic zwitterionic intermediates. With adequate modifications of both the electronic properties of the ketene and the reaction conditions, these elusive intermediates have been successfully trapped and fully characterized (X-ray), thus confirming the predicted stepwise nature of the transformation.

Open aryl triazole receptors: planar sheets, spheres and anion binding.

The morphology of the aggregates formed from the self-assembly of aryl triazole amphiphiles is disrupted upon the binding of a bromide anion due to the conformational changes experienced by these receptors.

A hydridoirida-beta-diketone as an efficient and robust homogeneous catalyst for the hydrolysis of ammonia-borane or amine-borane adducts in air to produce hydrogen.

The first homogeneous metal-catalysed hydrolysis of ammonia-borane or amine-borane adducts for hydrogen generation, using a stable organometallic complex [IrHCl{(PPh(2)(o-C(6)H(4)CO))(2)H}], is reported.