Non-coordinating Solvents Research Articles

Crystal structure of catena-poly[[[aqua-bis-(di-methyl-formamide-κO)magnesium(II)]-μ3-(2,2'-bi-pyridine-5,5'-di-carboxyl-ato-κ5O2:O2':N,N':O5)-[di-chlorido-platinum(II)]] di-methyl-formamide monosolvate

The title compound, {[MgPtCl2(C12H6N2O4)(C3H7NO)2(H2O)]·C3H7NO} n , is a one-dimensional coordination polymer. The structure consists of Pt-functionalized bi-pyridine ligands connected by MgII cations, as well as coordinating and non-coordinating solvent mol-ecules. The PtII cation is coordinated by the two N atoms of the bi-pyridine moiety and two Cl atoms in a square-planar fashion. This coordination induces an in-plane bend along the bi-pyridine backbone of approximately 10° from the linear ideal of a conjugated π-system. Likewise, the coordination to the MgII cation induces a significant bowing of the plane of the bi-pyridine of about 12°, giving it a distinct curved appearance. The carboxyl-ate groups of the bi-pyridine ligand exhibit moderate rotations relative to their parent pyridine rings. The MgII cation has a fairly regular octa-hedral coordination polyhedron, in which three vertices are occupied by O atoms from the carboxyl-ate groups of three different bi-pyridine ligands. The remaining three vertices are occupied by the O atoms of two di-methyl-formamide (DMF) mol-ecules and one water mol-ecule. The one-dimensional chains are oriented in the [01-1] direction, and non-coordinating DMF mol-ecules can be found in the space between the chains. The shortest inter-molecular O⋯H contacts are 2.844 (4) and 2.659 (4) Å, suggesting moderate hydrogen-bonding inter-actions. In addition, there is a short inter-molecular Pt⋯Pt contact of 3.491 (1) Å, indicating a Pt stacking inter-action. Some structure-directing contribution from the hydrogen bonding and Pt⋯Pt inter-action is probable. However, the crystal packing seems to be directed primarily by van der Waals inter-actions.

Recyclable Dirhodium(II) Catalyst Rh2(esp)2 for the Allylic Oxidation of Δ5-Steroids.

The chelating dirhodium(II) catalyst Rh2(esp)2 was shown to efficiently catalyze the allylic oxidation of Δ5-steroids using T-HYDRO (70% tert-butyl hydroperoxide in water) as oxidant. Reaction yields were affected by the coordination ability of the solvent. The noncoordinating solvent n-heptane was determined to be an optimal solvent. At gram scale, the product, Δ5-en-7-one steroid, precipitated from the reaction mixture. The Rh2(esp)2 complex did not undergo catalytic degradation and was recycled using Merrifield-pyridine resin for further allylic oxidation cycles. The results of ultraviolet/visible spectral analysis suggested that the Rh2(II,II) species, rather than the Rh2(II,III) species, was in the catalyst resting state during the reaction, which helps to explain the high durability of the catalyst.

Synthesis and Reduction of Sterically Encumbered Mesoionic Carbene-Stabilized Aryldihaloboranes.

Sterically hindered, in situ generated 1,3,4-substituted 1,2,3-triazol-5-ylidene mesoionic carbenes (MICs) were employed to stabilize a number of aryl- and heteroaryldihaloboranes, as well as the first MIC-supported diborane. Reduction of borane adducts of the 1-(2,6-diisopropylphenyl)-3-methyl-4-tert-butyl-1,2,3-triazol-5-ylidene ligand with KC8 in non-coordinating solvents led to intramolecular C-H- and, C-C-activation at an isopropyl residue of the supporting ligand. DFT calculations showed that each of these activation reactions proceeds via a different isomer of a borylene intermediate.

Dinuclear organotin(IV) coordination polymers derived from Schiff bases with l-aspartic acid

Reaction of sodium 2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene)amino)succinate and sodium (E)-2-((1-(2-hydroxyphenyl)ethylidene)amino)succinate (L1HNa2 and L2HNa2) in a 1:2 M ratio with Bz2SnCl2 in methanol gave dinuclear diorganotin(IV) complexes of composition [Bz2Sn(Lx)SnBz2Cl] (Lx = L1 (1) and L2 (2)). Reaction of L2HNa2 and Bz3SnCl (1:2) in anhydrous toluene under reflux conditions yielded the analogous chlorine-free product of composition [Bz2Sn(L2)SnBz3] (3) via cleavage of a Sn-C bond for one of the triorganotin precursor equivalents with elimination of toluene. In addition, the tributyltin(IV) compounds of composition [Bu3Sn(LxH)SnBu3] (Lx = L2 (4) and L3 (5)) were prepared in a single-step transformation by combining equimolar proportions of (Bu3Sn)2O, (S)-2-aminosuccinic acid and 2'-hydroxyacetophenone/2-hydroxybenzaldehyde in anhydrous methanol. The structures of the organotin(IV) compounds in solution were assessed using 1H, 13C and 119Sn NMR spectroscopic techniques, while the molecular structures of 1–5 were analyzed by single-crystal X-ray diffraction. In the solid state, complexes 1-3 exhibit one-dimensional coordination polymers with alternate six- and seven-coordinate tin atoms embedded in distorted monocapped trigonal-bipyramidal (1-2)/octahedral (3) and pentagonal-bipyramidal (1-2)/bicapped trigonal-bipyramidal (3) coordination environments. On the contrary, compounds 4–5 are two-dimensional coordination polymers based on 30-membered tetranuclear macrocyclic ring structures, in which the tin atoms comprise distorted trigonal-bipyramidal coordination polyhedra. However, in solution the polymeric structures of 1–5 dissociate to give dinuclear complexes, even in non-coordinating solvents such as chloroform.

Unusual cis-diprotonated forms and fluorescent aggregates of non-peripherally alkoxy-substituted metallophthalocyanines.

Protonation and aggregation of two metallophthalocyanines (zinc and magnesium) non-peripherally substituted with 1,4,7-trioxanonyl moieties were studied by steady-state and time-resolved optical spectroscopy. Both compounds are easily protonated in organic solvents, but the central metal ion strongly affects the character of this process. In particular, the magnesium derivative forms the cis-diprotonated isomer observed for the first time in phthalocyanines, in contrast to its zinc counterpart which forms the typical trans-diprotonated isomer. In addition, studies performed on phthalocyanines substituted with n-butoxy groups at their non-peripheral positions indicated that the formation of the cis-diprotonated forms is a more common feature of alkoxy-substituted magnesium metallophthalocyanines, in contrast to derivatives with other metal ions. The cis-diprotonated forms of the magnesium derivatives are formed at much lower proton concentrations than the trans-diprotonated forms of their zinc counterparts. The cis-isomers were also found to have more advantageous photophysical properties for photoactive applications than the trans-isomers. Aggregation studies of the trioxanonyl phthalocyanines revealed that the magnesium derivative aggregates much more easily in non-coordinating solvents than its zinc counterpart. Both the derivatives form fluorescent aggregates, which is typically attributed to the presence of oxygen-to-metal intermolecular coordination preventing the formation of non-fluorescent face-to-face stacks. The results indicate that the oxygen-to-metal coordination plays a significant role in the studied systems and the stronger oxygen-coordination ability of magnesium ions compared to zinc ions may underlie the observed differences between the phthalocyanines metallated with these two ions.

Continuous Flow Synthesis and Purification of Aryldiazomethanes through Hydrazone Fragmentation.

Electron-rich diazo compounds, such as aryldiazomethanes, are powerful reagents for the synthesis of complex structures, but the risks associated with their toxicity and instability often limit their use. Flow chemistry techniques make these issues avoidable, as the hazardous intermediate can be used as it is produced, avoiding accumulation and handling. Unfortunately, the produced stream is often contaminated with other reagents and by-products, making it incompatible with many applications, especially in catalysis. Herein is reported a metal-free continuous flow method for the production of aryldiazomethane solutions in a non-coordinating solvent from easily prepared, bench-stable sulfonylhydrazones. All by-products are removed by an in-line aqueous wash, leaving a clean, base-free diazo stream. Three successful sensitive metal-catalyzed transformations demonstrated the value of the method.

Influence of co-ordinating and non-coordinating solvents in structural and morphological properties of Cu2ZnSnS4 (CZTS) nanoparticles

Copper zinc tin sulphide Cu2ZnSnS4 (CZTS) nanoparticles were synthesized using different solvents including 1-octadecene (1-ODE), oleylamine (OLAM), oleic acid (OLA) and 1-dodecanethiol (1-DDT). Pure oleylamine based synthesis of nanoparticles results formation of nearly spherical like particles, while the pure oleic acid and mixture of oleylamine and oleic acid lead to the formation of hierarchical microspheres and nanodisc like structures. In addition to different morphologies, 1-dodecanethiol (1-DDT) based synthesis of Cu2ZnSnS4 nanoparticles posses wurtzite structure while rest of them exhibit pure kesterite phase. Further, the low volume of oleylamine in the reaction system motivates formation of sheet like structure. The mechanism involved in this structural direction of the nanoparticles into various morphologies was discussed. The synthesized CZTS nanoparticles were characterized using XRD, SEM, TEM and ATR-FTIR.

Mono- and binuclear tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate bismuth(III) dichloride complexes: a soft scorpionate ligand can coordinate to p-block elements.

Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination chemistry due to the ease of introduction of steric and electronic substitutions at the pyrazole rings. The development and use of the tris(pyrazolyl)hydroborate ligand, called a `scorpionate', were pioneered by the late Professor Swiatoslaw Trofimenko. He developed a second generation for his ligand system by the introduction of 3-tert-butyl and 3-phenyl substituents and this new ligand system accounted for many remarkable developments in inorganic and coordination chemistry in stabilizing monomeric species while maintaining an open coordination site. Bismuth is remarkably harmless among the toxic heavy metal p-block elements and is now becoming popular as a replacement for highly toxic metal elements, such as lead. Two bismuth(III) complexes of the anionic sulfur-containing tripod tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate ligand were prepared. By recrystallization from MeOH/CH2Cl2, orange crystals of dichlorido(methanol-κO)[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III), [Bi(C21H34BN6S3)Cl2(CH4O)], (I), were obtained, manifesting a mononuclear structure. By using a noncoordinating solvent, red crystals of the binuclear structure with bridging Cl atoms were obtained, namely di-μ-chlorido-bis{chlorido[tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl-κS)hydroborato]bismuth(III)}, [Bi2(C21H34BN6S3)2Cl4], (II). These complexes show {BiIIIS3Cl2O} and {BiIIIS3Cl3} coordination geometries with average BiIII-S bond lengths of 2.73 and 2.78 Å in (I) and (II), respectively. The overall BiIII coordination geometry is distorted octahedral due to stereochemically active lone pairs. The three BiIII-S bond lengths are almost equal in (I) but show considerable differences in (II), with one long and two shorter distances that also correlate with changes in the UV-Vis and 1H NMR spectra. For direct measurements of the Bi-S/Cl coordination, ligand K-edge X-ray absorption measurements were carried out in combination with ground and excited-state electronic structure analyses. For p-block elements, these sulfur-containing ligands are useful for preparing the appropriate complexes due to their flexible coordination geometry.

Supramolecular Aggregates of Defined Stereochemical Scaffolds: Aggregation/Deaggregation in Schiff-Base Zinc(II) Complexes Derived from Enantiopure trans-1,2-Diaminocyclohexane.

This contribution explores, through detailed 1H NMR, DOSY NMR, optical absorption, and circular dichroism spectroscopic studies, the aggregation properties in solution of noncoordinating solvents of some new ZnII Schiff-base complexes, (R)-1, (S)-1, and (R)-2, derived from the chiral trans-1,2-diaminocyclohexane. It is found that chloroform solutions of 1 are characterized by the presence of three species, the predominance of which consists of large oligomeric aggregates. For chloroform solutions of 1, upon heating or standing, all species are irreversibly converted into a dimer, 1C, which is very stable and hardly disaggregable. Analysis of 1H NMR, UV/vis, and CD spectroscopic data and chemical evidence allow proposing a double helicate Zn2L2 structure with a tetrahedral coordination around the ZnII ions for 1C, as a consequence of the defined stereochemistry of the trans-1,2-diaminocyclohexane chelate bridge. This represents a different, uncommon aggregation mode in ZnII complexes of tetradentate Schiff-bases.

ZnO nanonails: Organometallic synthesis, self-assembly and enhanced hydrogen gas production

We report the rational synthesis and characterizations of defect-rich zinc oxide (ZnO) nanonails that were prepared by organometallic approach and their implementation as an efficient photocatalyst for hydrogen (H2) generation. The ZnO nanonails were prepared from zinc stearate in n-octadecene that serves as non-coordinating solvent without the presence of any capping agent. Transmission electron microscopy (TEM) studies reveal that the individual triangular prismatic nanonail has an average edge length of 50–70nm and it appears to have preferred growth orientation along [0001] crystal axis. Intriguingly, this nanonails show oriented-attachment along the flat-basal edge and self-assembled into twinned structure. Such structure is interconnected via a narrow-gap to form symmetrical twinned-like nanonails with truncated tips at both ends. In comparison to ZnO commercial nanopowder, ZnO nanonails show significant enhancement in photocatalytic H2 gas generation rate of 53.33% under UV light for 5h. These results demonstrate ZnO nanonails to be a substantial potential photocatalyst for efficient photocatalytic applications.

Synthesis of Cu2ZnSnSe4 hierarchical nanostructures by colloidal method

Synthesis of Cu2ZnSnSe4 nanostructures have turned large interest among researchers. Among the other methods, colloidal method based synthesis of Cu2ZnSnSe4 nanostructures using non-aqueous solvents has been a subject of study in recent years. In the present work, different morphologies of Cu2ZnSnSe4 nanoparticles were synthesized using oleylamine (OLAM), oleic acid (OLA) and 1-octadecene (1-ODE) as solvents. It was found that the particles were of non-spherical in shape when OLAM was used and its morphology was significantly varied when equal volume of the OLA and 1-ODE was used. This clearly indicate the considerable influence of coordinating and non-coordinating solvents on morphology. In addition to this, hierarchical nanostructures of CZTSe were obtained when mixed solvents of OLAM/OLA with 1-ODE were used. X-ray diffraction analysis (XRD) shows the presence of tetragonal CZTSe through its characteristic peaks at (112), (204), and (312) planes. Scanning electron microscopy (SEM) analysis clearly shows its morphological variations which depended upon the solvent and solvent mixture. EDX analysis shows presence of elements Cu, Zn, Sn, Se in the synthesized products and non-stoichiometric in nature with deficient of Zn and Sn. The mechanism of influence and role of solvents in tuning of different morphology was analysed. The results are discussed in detail.

Hot-Injection Thermolysis of Cobalt Antimony Nanoparticles with Co(II)-Oleate and Sb(III)-Oleate

A novel strategy for the synthesis of CoSb₂ nanoparticles is demonstrated via preparation of novel organometallic complexes. Hydrated cobalt oleate (CoOl) and non-hydrated antimony oleate (SbOl) complexes are synthesized as precursors. The CoSb₂ nanoparticles are prepared by hot injection, which involves thermolysis of CoOl and SbOl in a non-coordinating solvent at 320 ℃. The coordination modes and distinct thermal behaviors of the intermediate non-hydrated SbOl complexes are comparatively investigated by thermo-analytical techniques. When the reaction temperature is increased, the particle size is found to increase linearly. The crystallinity of the CoSb2 nanoparticles prepared at 250℃ is amorphous phase without any peaks. CoSb₂ structural peaks start to appear at 300℃ and dominant peaks with high crystallinity are synthesized at 320℃. The potential chemical structures of non-hydrated SbOl and their reaction mechanisms by thermolysis are elucidated. The elemental composition and crystallographic structure of CoSb₂ nanoparticles suggest a bimodal interaction of the organic shell and the nanoparticle surface, with a chemical absorbed inner layer and physically absorbed outer layer of carboxylic acid.

Solvent Effects for Spectroscopic Properties of Near-Infrared Absorbing Nickel–Dithiolene Complex [Ni(iPr2timdt)2] (iPr2timdt: Monoanion of 1,3-Diisopropylimidazolidine-2,4,5-trithione)

Abstract The near-infrared (NIR) absorption properties of a square-planar nickel–dithiolene complex [Ni(iPr2timdt)2] in various organic solvents have been investigated (iPr2timdt denotes a monoanion of 1,3-diisopropylimidazolidine-2,4,5-trithione). In non-coordinating aprotic organic solvents of smaller relative permittivity (εr < 10) such as dichloromethane (εr = 8.9), the neutral complex [Ni(iPr2timdt)2]0 shows a huge and sharp NIR absorption band at ca. 1000 nm having the molar absorptivity of ε = 6–8 × 104 L mol−1 cm−1. In contrast, in strongly coordinating solvents such as pyridine (Gutmann’s donor number, DN = 33.1), the NIR absorption of [Ni(iPr2timdt)2]0 disappears most probably, owing to the coordination of pyridine molecules onto the axial sites of this square-planar complex. In high relative permittivity solvents such as N,N-dimethylformamide (DMF, εr = 36.71), [Ni(iPr2timdt)2]0 (λmax: ca. 1000 nm) undergoes spontaneous reduction reactions yielding the ionic complexes of [Ni(iPr2timdt)2]− (λmax: ca. 1400 nm) and [Ni(iPr2timdt)2]2− (no NIR peaks), which is indeed reconciled with the results of the spectroelectrochemical measurements. It is stressed that the absorption properties of [Ni(iPr2timdt)2] in the NIR region are sensitive to the solvent properties, and these complex systems serve as NIR probes to report solvent properties.

ChemInform Abstract: An Enantioselective Approach to 4‐O‐Protected‐2‐cyclopentene‐l,4‐diol Derivatives via a Rhodium‐Catalyzed Redox‐Isomerization Reaction.

Kinetic resolution of a series of cyclopentene-1,4-diol derivatives has been successfully achieved with enantiomeric excess up to 99.4% and a kf/ks ratio of 55 by a rhodium-catalyzed redox-isomerization reaction in a noncoordinating solvent.

Iron oxide and iron carbide particles produced by the polyol method

Iron oxide (γ-Fe2O3) and iron carbide (Fe3C) particles were produced by the polyol method. Ferrocene, which was employed as an iron source, was decomposed in a mixture of 1,2-hexadecandiol, oleylamine, and 1-octadecene. Particles were characterized using Mossbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. It was found that oleylamine acted as a capping reagent, leading to uniform-sized (12-16 nm) particles consisting of γ-Fe 2O3. On the other hand, 1-octadecene acted as a non-coordinating solvent and a carbon source, which led to particles consisting of Fe3C and α-Fe with various sizes.

Synthesis, characterization, single crystal XRD and biological screenings of organotin(IV) derivatives with 4-(2-hydroxyethyl)piperazine-1-carbodithioic acid

Organotin(IV) thiocarboxylates R2SnL2 (R = Me: 1: Ph: 2)/R2(Cl)SnL (R = n-Bu: 3; Ph: 4)/R3SnL (R = Me: 5; n-Bu: 6; Ph: 7), where L = 4-(2-hydroxyethyl)piperazine-1-carbodithioate, have been synthesized by stirring together 1,2-hydroxyethylpiperazine and CS2 in methanol, and then refluxing with a di-/triorganotin chloride. The synthesized products have been characterized by various spectroscopic (IR, 1H NMR, 13C NMR, EI-MS) techniques and single crystal XRD. FT-IR data indicate bidentate binding of the ligand. The magnitude of 2J(119Sn–1H) demonstrated a skew trapezoidal environment around tin(IV) in 1, whereas the metal geometry in 5 was between distorted tetrahedral and trigonal bipyramidal in solution. 13C NMR revealed four- and five-coordinate environments in 6 and 7, respectively, in non-coordinating solvent. EI-MS data agreed very well with the structural skeleton of the products. Single crystal XRD study has shown skew trapezoidal- and trigonal-bipyramidal Sn(IV) in 1 and 7, respectively. Compound 6 interacted with salmon sperm DNA (SS-DNA) with significant hypochromic effect and an intercalating mode of binding. Diorganotin(IV) derivatives (2 and 3) generally exhibited poor antibacterial/antifungal potential as compared to their trialkyltin(IV)/triaryltin(IV) counterparts (5 and 6). The in vitro hemolytic activities show that average lysis of human red blood cells caused by 1–7 was significantly lower compared to triton X-100 (positive control, 100% lysis) and not very much higher than PBS (negative control, 0% lysis).

Chemically synthesized CdSe quantum dots inhibit growth of human lung carcinoma cells via ROS generation.

Quantum dots (QDs), semiconducting materials have potential applications in the field of electronic and biomedical applications including cancer therapy. In present study, cadmium selenide (CdSe) QDs were synthesized by chemical method. Octadecene was used as non-coordinating solvent which facilitated the formation of colloidal solutions of nanoparticles. CdSe QDs were characterized by UV-vis spectrometer and transmission electron microscope (TEM). The size measured by TEM was varied between 2-5 nm depending upon temperature. The cytotoxic activity of QDs was monitored by MTT assay, nuclear condensation, ROS activity and DNA fragmentation assay on human lung epithelial A549 cell line. Cells were treated with different concentrations of varying size of CdSe QDs for 24 h. CdSe QDs induced significant (p < 0.05) dose dependent cytotoxicity and this was comparable to the sizes of particles. Smaller particles were more cytotoxic to the large particles. Fluorescence microscopic analysis revealed that QDs induced oxidative stress generating significant ROS level and consequently, induced nuclear condensation and DNA fragmentation. Study suggested the cytotoxicity of CdSe QDs via ROS generation and DNA fragmentation depending upon particles size.

Ligand-centred oxidative chemistry in sterically hindered salen complexes: an interesting case with nickel.

Salen ligands are ubiquitous ligands because they can be readily prepared by condensation of a diamine with two equivalents of salicylaldehyde. They form stable complexes with a great variety of metal ions and find applications in various fields, especially catalysis. The introduction of chirality at the bridge and the adjunction of sterically demanding tert-butyl groups in ortho and para positions of the phenols allow for efficient enantioselective catalysis. On the other hand, early investigations on the oxidation chemistry of phenols highlighted that the incorporation of tert-butyl groups in ortho and para positions can stabilize enormously the one-electron oxidized product e.g. the phenoxyl radical. The redox-activity of sterically hindered salen ligands will be discussed in this perspective article. We will focus our attention on nickel salen complexes since both the metal and the ligand are potentially redox-active, while the oxidized products are stable enough to be characterized by EPR and NIR spectroscopies. Additionally, the one-electron oxidized species could be isolated as single crystals in some instances, giving detailed pictures of their electronic structure. Both the Ni(ii)-radical and Ni(iii) bis(phenolate) valence tautomers are accessible upon one-electron oxidation. The substituents, metal coordination sphere, solvent and temperature are crucial factors that dictate the electronic structure of these one-electron oxidized salen complexes.

An Enantioselective Approach to 4-O-Protected-2-cyclopentene-l,4-diol Derivatives via a Rhodium-Catalyzed Redox-Isomerization Reaction.

Kinetic resolution of a series of cyclopentene-1,4-diol derivatives has been successfully achieved with enantiomeric excess up to 99.4% and a kf/ks ratio of 55 by a rhodium-catalyzed redox-isomerization reaction in a noncoordinating solvent.

Preparation of cadmium selenide colloidal quantum dots in non-coordinating solvent octadecene

Nearly monodisperse cadmium selenide quantum dots (QDs) were synthesized in non-coordinating solvent octadecene through phosphine-free method using oleic acid as surfactant. Selenium powder suspension in octadecene obtained by ultrasound processing was used as one of precursor solutions. Influence of multiple selenium precursor injections on nanocrystal growth process was investigated. Nanoparticles were characterized by means of absorption and photoluminescence spectroscopies.