The compounds, Li3MZn5(BH4)15, M = Mg and Mn, represent the first trimetallic borohydrides and are also new cationic solid solutions. These materials were prepared by mechanochemical synthesis from LiBH4, MCl2 or M(BH4)2, and ZnCl2. The compounds are isostructural, and their crystal structure was characterized by in situ synchrotron radiation powder X-ray and neutron diffraction and DFT calculations. While diffraction provides an average view of the structure as hexagonal (a = 15.371(3), c = 8.586(2) Å, space group P63/mcm for Mg-compound at room temperature), the DFT optimization of locally ordered models suggests a related ortho-hexagonal cell. Ordered models that maximize Mg-Mg separation have the lowest DFT energy, suggesting that the hexagonal structure seen by diffraction is a superposition of three such orthorhombic structures in three orientations along the hexagonal c-axis. No conclusion about the coherent length of the orthorhombic structure can be however done. The framework in Li3MZn5(BH4)15 is of a new type. It contains channels built from face-sharing (BH4)6 octahedra. While X-ray and neutron powder diffraction preferentially localize lithium in the center of the octahedra, thus resulting in two weakly interconnected frameworks of a new type, the DFT calculations clearly favor lithium inside the shared triangular faces, leading to two interpenetrated mco-nets (mco-c type) with the basic tile being built from three tfa tiles, which is the framework type of the related bimetallic LiZn2(BH4)5. The new borohydrides Li3MZn5(BH4)15 are potentially interesting as solid-state electrolytes, if the lithium mobility within the octahedral channels is improved by disordering the site via heterovalent substitution. From a hydrogen storage point of view, their application seems to be limited as the compounds decompose to three known metal borohydrides.
A four-step synthesis of 1-substituted 5-(2-aminophenyl)-1H-pyrazoles 5 as a novel type of histamine analogs and versatile building blocks for further transformations was developed. The synthesis starts from commercially available 2-nitroacetophenone (12), which is converted into the enamino ketone 13 as the key intermediate. Cyclization of the key intermediate 13 with monosubstituted hydrazines 14a -14l afforded the 5-(2-nitrophenyl)-1H-pyrazoles 17a -17l. Finally, catalytic hydrogenation of the nitro compounds 17a, 17c -17e, and 17g -17j furnished the title compounds 5a, 5c -5e, and 5g -5j, respectively, in good yields. As demonstrated by some further transformations, additional functionalization of compounds 17 and 5 is feasible, either by electrophilic substitution at C(4) of the pyrazole ring, or at the NH 2 group.Introduction. -In biological processes, histamine, tyramine, dopamine, tryptamine, serotonin, and melatonin play a crucial role as chemical messengers. Therefore, preparation of their novel synthetic analogs based on the 2-(heteroaryl)ethylamine scaffold is an important target in medicinal and synthetic organic chemistry [1].Pyrazoles are an important class of heterocyclic compounds. Despite their rare occurrence in nature, numerous pyrazole derivatives have found use in various applications, and a general interest in their chemistry is still continuing (for a review, see [2]). Among numerous synthetic options for the construction of the pyrazole ring, two classical approaches are most frequently employed: a) cyclocondensation of a 1,3-dicarbonyl compound with a hydrazine derivative and b) 1,3-dipolar cycloaddition of a CÀNÀN type 1,3-dipole (diazoalkane, nitrile imine, or azomethine imine) to a C,C multiple bond [2].Recently, a part of our research has been focused on the synthesis of functionalized pyrazoles utilizing the
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