Hydroxamate-Based Metal-Organic Frameworks.

This mini-review focuses on recent developments in hydroxamate-based metal-organic frameworks (MOFs), which exhibit unique structures and properties distinct from those of carboxylate-based MOFs. Hydroxamates (RCONHO) form MOFs with novel structural motifs and functionalities. In this review, synthetic strategies, structural characteristics, and functional applications of key examples of hydroxamate-based MOFs are described, providing insights into the influence of the hydroxamate ligand on the MOF properties compared to that of the carboxylate-based analogues.

Bis(methylene)-λ-phosphane anions.

Bis(methylene)-λ-phosphane anions, , anionic phosphorus-centered heteroallene-type molecules, were obtained from the desilylation of a bis(silyl)methyl-substituted phosphaalkene. Their molecular structures, which were determined using spectroscopic techniques and single-crystal X-ray diffraction analysis, suggest that the central di-coordinated P atom is engaged in cumulative C[double bond, length as m-dash]P[double bond, length as m-dash]C π-bonds with the neighboring C atoms. The π-bond character of the C[double bond, length as m-dash]P[double bond, length as m-dash]C moieties was examined on the basis of the experimental results in combination with theoretical calculations; the results obtained suggest that multiple silyl substitutions at the C atom weaken the C[double bond, length as m-dash]P π-bonding character.

A tin analogue of propadiene with cumulated C[double bond, length as m-dash]Sn double bonds.

The synthesis, structure, and properties of a stable, linear 2-stannapropadiene are reported. The identical C[double bond, length as m-dash]Sn bonds in this 2-stannapropadiene are the shortest hitherto reported C-Sn bonds. This 2-stannapropadiene features a Sn NMR signal at 507 ppm for the central tin atom, indicative of an unsaturated Sn oxidation state.

Reactivity of a Linear 2-Germapropadiene with Acids, Ketones, and Amines.

The reactivity of an isolable 2-germapropadiene with acids, ketones, and amines was investigated. The reactions of 2-germapropagiene 1 with hydrogen chloride and acetic acid afforded the corresponding dichlorogermane (2) and diacetoxygermane (3), respectively, indicating that the central germanium atom of 1 is electrophilic. The reaction of 1 with benzaldehyde proceeds via a formal [2+2] cycloaddition to afford the corresponding spiro compound (4).

Phosphoramide-Based Metal-Organic Frameworks for Effective Gas Adsorption.

Cost-effective and facile synthetic routes to organic ligands, along with porous materials that exhibit exceptional gas-storage properties, promise significant industrial applications. Here, a two-step synthesis of novel organophosphorus ligands without metal catalysts is reported. These ligands serve as versatile linkers for the construction of metal-organic frameworks (MOFs) incorporating various metal ions, including zinc and copper.

Alkoxy-Functionalized Hydroxamate/Zinc Metal-Organic Frameworks and the Effects of Substituents and Acid Addition on Their Structures.

Single crystals of alkoxy-functionalized hydroxamate/zinc metal-organic frameworks (MOFs) were obtained by fixating the hydroxamate moiety via intramolecular hydrogen bonding. The resulting MOF structures depend on the steric demand of the alkoxy groups, whereby the incorporation of bulky isopropyl groups affords porous hydroxamate/zinc MOFs. The topological structures of the isopropyl-substituted MOFs could be controlled by adding acid.

Zn-Based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties.

Invited for the cover of this issue is the group of Koh Sugamata, Mao Minoura, and co-workers at Rikkyo University. The image depicts triptycene-based metal-organic frameworks with honeycomb structures that collect carbon dioxide and hydrogen, in an analogy to bees collecting honey in their honeycombs. Read the full text of the article at 10.

Zn-Based Metal-Organic Frameworks Using Triptycene Hexacarboxylate Ligands: Synthesis, Structure, and Gas-Sorption Properties.

A series of metal-organic frameworks (MOFs) based on zinc ions and two triptycene ligands of different size have been synthesized under solvothermal conditions. Structural analyses revealed that they are isostructural 3D-network MOFs. The high porosity and thermal stability of these MOFs can be attributed to the highly rigid triptycene-based ligands.

2-Heteraallenes.

While analogues of allenes with heavier main-group elements (group 14-16) have been extensively studied, 2-heteraallenes are rare chemical species whose properties are mostly unknown. It is also notable that the synthesis and isolation of allene-type molecules are not widespread, despite the extensive study of two-coordinated low-valent chemical species.

A Linear C=Ge=C Heteroallene with a Di-coordinated Germanium Atom.

Allenes (>C=C=C<) are classified as cumulated dienes with a linear structure and an sp-hybridized central carbon atom. We have synthesized and isolated a stable 2-germapropadiene with bulky silyl substituents. The 2-germapropadiene allene moiety adopts a linear structure both in the solid state and in solution.

Controlling the Flexibility of Carbazole-Based Metal-Organic Frameworks by Substituent Effects.

We have developed highly porous Cu-based metal-organic frameworks (MOFs) using carbazole-type linkers. The novel topological structure of these MOFs was revealed by single-crystal X-ray diffraction analysis. Molecular adsorption/desorption experiments indicated that these MOFs are flexible and change their structure upon adsorption/desorption of organic solvents and gas molecules.

Tellurium-Centered Bent Allenes: Synthesis, Characterization, and Reactivity.

Compounds with multiple bonds between elements of the second and fifth periods are extremely unstable, and systematic investigations into their properties remain elusive. Herein, we report a tellurium-centered heteroallene that contains multiple bonds between carbon and tellurium. This compound is the first example of bis(methylene)-λ-tellane, which was synthesized and fully characterized using multinuclear NMR spectroscopy and X-ray crystallography.

Structural analysis of interpenetrated methyl-modified MOF-5 and its gas-adsorption properties.

The first example of an interpenetrated methyl-modified MOF-5 with the formula ZnO(DMBDC)(DMF), where DMBDC is 2,5-dimethylbenzene-1,4-dicarboxylate and DMF is N,N-dimethylformamide (henceforth denoted as MeMOF-5-int), namely, poly[tris(μ-2,5-dimethylbenzene-1,4-dicarboxylato)bis(N,N-dimethylformamide)-μ-oxido-tetrazinc(II)], [Zn(CHO)O(CHNO)], has been obtained from a solvothermal synthesis of 2,5-dimethylbenzene-1,4-dicarboxylic acid and Zn(NO)·6HO in DMF. A systematic study revealed that the choice of solvent is of critical importance for the synthesis of phase-pure MeMOF-5-int, which was thoroughly characterized by single-crystal and powder X-ray diffraction (PXRD), as well as by gas-adsorption analyses. The Brunauer-Emmett-Teller surface area of MeMOF-5-int (660 m g), determined by N adsorption, is much lower than that of nonpenetrated MeMOF-5 (2420 m g).

Structural analysis of and selective CO adsorption in mixed-ligand hydroxamate-based metal-organic frameworks.

Two mixed-ligand metal-organic frameworks, [Zn(BDHA)(INA)] (MOF-1: HBDHA = benzene-1,4-dihydroxamic acid; HINA = isonicotinic acid) and [Co(BDHA)(INA)(DMF)] (MOF-2), were solvothermally synthesized and fully characterized by single-crystal X-ray crystallography as well as N, H, and CO gas-sorption measurements. The results constitute the first detailed analysis of the bonding environment around the hydroxamates in such MOFs, which are simultaneously decorated with Lewis-basic sites from the hydroxamate moieties and metal sites predisposed for coordinative unsaturation. MOF-2 shows a desirably selective adsorption of CO relative to N.

(Thio)(silyl)carbene and (seleno)(silyl)carbene gold(i) complexes from the reaction of bis(methylene)-λ-sulfane and bis(methylene)-λ-selane with chloro(dimethylsulfide)gold(i).

The dinuclear (thio)(silyl)carbene and (seleno)(silyl)carbene gold(i) complexes 1 and 2 were obtained from the reaction of two equivalents of AuCl(SMe) with the stable bis(methylene)-λ-chalcogenanes 3 and 4, respectively. The reaction proceeds under elimination of the chlorosilane moiety of 3 and 4. Complexes 1 and 2 were characterized by spectroscopic and X-ray diffraction (XRD) analyses.

Group 2 metal bis(arenecarbochalcogenoate)(crown ether) complexes: isolation and structural analysis.

A series of Group 2 metal bis(arenecarbochalcogenoato)(crown ether) complexes M(EE'CAr)2(L)(L')x (M = Mg, Ca, Sr, Ba; Ar = aryl; E = S, Se; E' = O, S; L = H2O or THF; L' = 15-crown-5, 18-crown-6) were synthesized and their structures were revealed by X-ray analyses. The two carbothioato ligands in Mg, Ca and Sr 15-crown-5 complexes are located on the same side of the crown ether plane, while those in Mg, Ca, Sr, and Ba 18-crown-6 compounds are on both sides of the 18-crown-6 plane (trans relative to the plane). For the Ca 15-crown-5 complex, both carbothioato ligands are connected to the central Ca ion through an oxygen atom in a monodentate manner, and the two hydrogen atoms of the coordinated water molecule are intramolecularly hydrogen-bonded with thiocarbonyl sulfur atoms.

Synthesis and Structure of a Stable Bis(methylene)-λ -sulfane.

Bis(methylene)-λ -sulfane 1, a >C=S=C< heterocumulene, was obtained as a red crystalline solid from the reaction between elemental sulfur and a carbenoid that contains sterically demanding silylalkyl groups. Under atmospheric conditions, and even at elevated temperatures, 1 exhibits extraordinary stability. The molecular structure and electron-density distribution of 1 were analyzed by single-crystal X-ray diffraction analysis, which revealed a bent C=S=C geometry with C=S=C π-bonds.

Reaction of a diaryldigermyne with ethylene.

Reaction of the stable digermyne BbtGe[triple bond, length as m-dash]GeBbt (Bbt = 2,6-[CH(SiMe)]-4-[C(SiMe)]-CH) with ethylene initially afforded the corresponding 1,2-digermacyclobutene. Depending on the reaction conditions applied, further reaction of this 1,2-digermacyclobutene with ethylene furnished two different reaction products: a 1,4-digermabicyclo[2.2.