Оценка экологической опасности рассеивания газопылевого облака при массовых взрывах в карьерах

Heteroanion (HA) moieties have a key role in templating of heteropolyoxometalate (HPA) architectures, but clusters templated by two different templates are rarely reported. Herein, we show how a cross-shaped HPA-based architecture can self-sort the HA templates by pairing two different guests into a divacant {XYW₁₅O₅₄} building block, with four of these building block units being linked together to complete the cross-shaped architecture. We exploited this observation to incorporate HA templates into well-defined positions within the clusters, leading to the isolation of a collection of mixed-HA templated cross-shaped polyanions [(XYW₁₅O₅₄)₄(WO₂)₄]^32–/36– (X = H–P, Y = Se, Te, As). The template positions have been unambiguously determined by single crystal X-ray diffraction, NMR spectroscopy, and high-resolution electrospray ionization mass spectrometry; these studies demonstrated that the mixed template containing HPA clusters are the preferred products which crystallize from the solution. Theoretical studies using DFT calculations suggest that the selective self-sorting originates from the coordination of the template in solution. The cross-shaped polyoxometalate clusters are redox-active, and the ability of molecules to accept electrons is slightly modulated by the HA incorporated as shown by differential pulse voltammetry experiments. These results indicate that the cross-shaped HPAs can be used to select templates from solution, and themselves have interesting geometries, which will be useful in developing functional molecular architectures based upon HPAs with well-defined structures and electronic properties

Synthesis and Characterization of a Series of [M₂(β-SiW₈O₃₁)₂]^<i>n</i>− Clusters and Mechanistic Insight into the Reorganization of {β-SiW₈O₃₁} into {α-SiW₉O₃₄}

Lacunary polyoxometalates of low nuclearity are difficult to synthesize in isolation. We report the facile synthesis of six {M₂(B-β-SiW₈O₃₁)₂} clusters (M = Co/Mn/Ni/Zn/Cu²⁺, Fe³⁺) that can be employed as building blocks for the formation of larger architectures. We show for the first time that such {B-β-SiW₈O₃₁} lacunae are capable of reorganizing into larger Keggin lacunary species even in the absence of an external source of tungstate. We hypothesize, based on electrospray ionization mass spectrometry evidence obtained, not only that such a transformation is only possible via an initial decomposition of the {SiW₈} precursor into a {SiW₆}-based intermediate but also that it is this {SiW₆} species that acts as the template for the growth of the larger fragments

Exploring the Assembly of Supramolecular Polyoxometalate Triangular Morphologies with Johnson Solid Cores: [(Mn^II(H₂O)₃)₂(K⊂{α-GeW₁₀Mn^II₂O₃₈}₃)]^19–

A new polyoxometalate (POM) cluster compound is presented which incorporates a trimeric assembly of Keggin-type germanotungstate fragments trapping a Johnson-type solid {Mn₈} core. The mixed K–Li salt of the polyanion [(Mn^II(H₂O)₃)₂(K⊂{α-GeW₁₀Mn^II₂O₃₈}₃)]^19– was characterized in the solid state and solution. The correlation of the assembly processes and the observed architecture of the “trinity” family of POMs is discussed

Protecting Group Free, Stereocontrolled Synthesis of β-Halo-enamides

Enamides, dienamides, and enynamides are important building blocks in synthetic, biological, and medicinal chemistry as well as materials science. Despite the extensive breath of their potential utility in synthetic chemistry, there is a lack of simple, high-yielding methods to deliver them efficiently and as single isomers. In this paper, we present a novel, protecting group free, efficient, and stereoselective approach to the generation of β-halo-enamides. The methodology presented provides a robust synthetic platform from which <i>E</i>- or <i>Z</i>-enamides can be generated in good yields and with complete stereocontrol

Solution-Phase Monitoring of the Structural Evolution of a Molybdenum Blue Nanoring

The inorganic host–guest complex Na₂₂{[Mo^VI₃₆O₁₁₂(H₂O)₁₆]⊂[Mo^VI₁₃₀Mo^V₂₀O₄₄₂(OH)₁₀(H₂O)₆₁]}·180H₂O ≡ {Mo₃₆}⊂{Mo₁₅₀}, compound <b>1</b>, has been isolated in its solid crystalline state via unconventional synthesis in a custom flow reactor. Carrying out the reaction under controlled flow conditions selected for the generation of {Mo₃₆}⊂{Mo₁₅₀} as the major product, allowing it to be reproducibly isolated in a moderate yield, as opposed to traditional “one-pot” batch syntheses that typically lead to crystallization of the {Mo₃₆} and {Mo₁₅₀} species separately. Structural and spectroscopic studies of compound <b>1</b> and the archetypal Molybdenum Blue (MB) wheel, {Mo₁₅₀}, identified compound <b>1</b> as a likely intermediate in the {Mo₃₆} templated synthesis of MB wheels. Further evidence illustrating the template effect of {Mo₃₆} to MB wheel synthesis was indicated by an increase in the yield and rate of production of {Mo₁₅₀} as a direct result of the addition of preformed {Mo₃₆} to the reaction mixture. Dynamic light scattering (DLS) techniques were also used to corroborate the mechanism of formation of the MB wheels through observation of the individual cluster species in solution. DLS measurement of the reaction solutions from which {Mo₃₆} and {Mo₁₅₀} crystallized gave particle size distribution curves averaging 1.9 and 3.9 nm, consistent with the dimensions of the discrete clusters, which allowed the use of size as a possible distinguishing feature of these key species in the reduced acidified molybdate solutions and to observe the templation of the MB wheel by {Mo₃₆} directly

Protecting Group Free, Stereocontrolled Synthesis of β-Halo-enamides

Enamides, dienamides, and enynamides are important building blocks in synthetic, biological, and medicinal chemistry as well as materials science. Despite the extensive breath of their potential utility in synthetic chemistry, there is a lack of simple, high-yielding methods to deliver them efficiently and as single isomers. In this paper, we present a novel, protecting group free, efficient, and stereoselective approach to the generation of β-halo-enamides. The methodology presented provides a robust synthetic platform from which <i>E</i>- or <i>Z</i>-enamides can be generated in good yields and with complete stereocontrol

Protecting Group Free, Stereocontrolled Synthesis of β-Halo-enamides

Enamides, dienamides, and enynamides are important building blocks in synthetic, biological, and medicinal chemistry as well as materials science. Despite the extensive breath of their potential utility in synthetic chemistry, there is a lack of simple, high-yielding methods to deliver them efficiently and as single isomers. In this paper, we present a novel, protecting group free, efficient, and stereoselective approach to the generation of β-halo-enamides. The methodology presented provides a robust synthetic platform from which <i>E</i>- or <i>Z</i>-enamides can be generated in good yields and with complete stereocontrol

Highly Efficient Synthesis of the Tricyclic Core of Taxol by Cascade Metathesis

An efficient enantioselective synthesis of the ABC tricyclic core of the anticancer drug Taxol is reported. The key step of this synthesis is a cascade metathesis reaction, which leads in one operation to the required tricycle if appropriate fine-tuning of the dienyne precursor is performed

Synthetic Considerations in the Self-Assembly of Coordination Polymers of Pyridine-Functionalized Hybrid Mn-Anderson Polyoxometalates

The incorporation of polyoxometalates (POMs) as structural units into ordered porous constructs such as metal–organic frameworks (MOFs) is desirable for a range of applications where intrinsic properties inherited from both the MOF and POM are utilized, including catalysis and magnetic data storage. The controlled self-assembly of targeted MOF topologies containing POM units is hampered by the wide range of oxo and hydroxo units on the peripheries of POMs that can act as coordinating groups toward linking metal cations leading to a diverse range of structures, but incorporation of organic donor units into hybrid POMs offers an alternative methodology to programmably synthesize POM/MOF conjugates. Herein, we report six coordination polymers obtained serendipitously wherein Zn²⁺ and Cu²⁺ link pyridine-appended Mn-Anderson clusters into two- and three-dimensional network solids with complex connectivities and topologies. Careful inspection of their solid-state structures has allowed us to identify common structure-directing features across these coordination polymers, including a square motif where two Zn²⁺ cations bridge two POMs. By correlating certain structural motifs with synthetic conditions, we have formulated a series of design considerations for the self-assembly of coordination polymers of hybrid POMs, encompassing the selection of reaction conditions, coligands, and linking metal cations. We anticipate that these synthetic guidelines will inform the future assembly of hybrid POMs into functional MOF materials

Solution-Phase Monitoring of the Structural Evolution of a Molybdenum Blue Nanoring

The inorganic host–guest complex Na₂₂{[Mo^VI₃₆O₁₁₂(H₂O)₁₆]⊂[Mo^VI₁₃₀Mo^V₂₀O₄₄₂(OH)₁₀(H₂O)₆₁]}·180H₂O ≡ {Mo₃₆}⊂{Mo₁₅₀}, compound <b>1</b>, has been isolated in its solid crystalline state via unconventional synthesis in a custom flow reactor. Carrying out the reaction under controlled flow conditions selected for the generation of {Mo₃₆}⊂{Mo₁₅₀} as the major product, allowing it to be reproducibly isolated in a moderate yield, as opposed to traditional “one-pot” batch syntheses that typically lead to crystallization of the {Mo₃₆} and {Mo₁₅₀} species separately. Structural and spectroscopic studies of compound <b>1</b> and the archetypal Molybdenum Blue (MB) wheel, {Mo₁₅₀}, identified compound <b>1</b> as a likely intermediate in the {Mo₃₆} templated synthesis of MB wheels. Further evidence illustrating the template effect of {Mo₃₆} to MB wheel synthesis was indicated by an increase in the yield and rate of production of {Mo₁₅₀} as a direct result of the addition of preformed {Mo₃₆} to the reaction mixture. Dynamic light scattering (DLS) techniques were also used to corroborate the mechanism of formation of the MB wheels through observation of the individual cluster species in solution. DLS measurement of the reaction solutions from which {Mo₃₆} and {Mo₁₅₀} crystallized gave particle size distribution curves averaging 1.9 and 3.9 nm, consistent with the dimensions of the discrete clusters, which allowed the use of size as a possible distinguishing feature of these key species in the reduced acidified molybdate solutions and to observe the templation of the MB wheel by {Mo₃₆} directly