Post-Synthetic Modification of a 1D Mixed-Linker Zn(II) Coordination Polymer for Acid-Catalyzed Alcoholysis of Epoxides

Rational design of heterogeneous acid catalysts possessing uniform dispersion of active sites plays a significant role in the catalytic performance. In the present work, a coordination polymer, [Zn(4,4'-bpy)(μ-Hbtc)(H2O)] ⋅ 2H2O (Zn-CP), was solvothermally synthesized using 4,4'-bpy (=4,4'-bipyridine) and H3btc (=1,3,5-benzenetricarboxylic acid) mixed linkers. Single crystal X-ray analysis of the polymer displayed that Zn-CP chains were decorated with 4,4'-bpy having unidentate coordination fashion. Then, the free N atom of the linker in Zn-CP was functionalized by -SO3H groups to afford Zn-CP-SO3H with enhanced acidity. The structures were characterized by FT-IR, thermogravimetric analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of NH3 (NH3-TPD), and field emission scanning electron microscopy (FE-SEM) analyses. The coordination polymer was employed as a heterogeneous catalyst for the alcoholysis of epoxides under room conditions. Zn-CP-SO3H exhibited excellent catalytic activity and regioselectivity in the methanolysis of styrene oxide within short reaction time.

Evaluation of the catalytic activity of Zn-MOF-74 for the alcoholysis of cyclohexene oxide

In the present work, nanocrystalline Zn-MOF-74 is shown to be a heterogeneous catalyst for the acid-catalyzed ring-opening alcoholysis of cyclohexene oxide. The results corroborated that accessible open metal sites within the material are critical conditions (Zn(ii) Lewis acid sites) for this reaction. Zn-MOF-74 was tested at three different temperatures (30, 40, and 50 °C) for the alcoholysis reaction. Furthermore, the cyclohexene oxide conversion was 94% in less than two days. A comparison of the catalytic activity with different crystal sizes of Zn-MOF-74 and the homogenous phase, zinc acetate, was conducted. Zn-MOF-74 exhibited excellent catalytic cyclability for three cycles without losing its activity. The material showed chemical stability by retaining its crystalline structure after the reaction and cyclability process.

Synthesis of rare-earth metal complexes with a morpholine-functionalized β-diketiminato ligand and their catalytic activities towards C–O and C–N bond formation

Unusual tridentate β-diketiminato rare-earth metal chlorides LRECl(µ-Cl)2Li(THF)2 (RE = Y (1a), Yb (1b), Lu (1c); L = MeC(NDipp)CHC(Me)N(CH2)2NC4H8O; Dipp = 2,6-iPr2C6H3) and the corresponding dialkyl complexes LRE(CH2SiMe3)2 (RE = Y...

Architectural and catalytic aspects of designer materials built using metalloligands of pyridine-2,6-dicarboxamide based ligands

This perspective presents the design, synthesis and crystal structures of a large number of architectures constructed using assorted metalloligands of pyridine-2,6-dicarboxamide based ligands. The metalloligands offered various appended functional groups, whereas design strategies included varying both their position and number. A combination of these parameters resulted in the development of assorted architectures including discrete trinuclear and tetranuclear complexes as well as 1D/2D/3D coordination polymers. The metalloligand strategy not only assisted in the construction of ordered crystalline materials with varied dimensionalities but also judiciously allowed the incorporation of Lewis acidic and redox-active secondary metals in the resultant architectures. As a result, such designer architectures illustrated their noteworthy role both as homogenous and heterogeneous catalysts in different organic transformation reactions.

Nucleophilic Transformations of Lewis Acid-Activated Disubstituted Epoxides with Catalyst-Controlled Regioselectivity

Due to their inherent ring strain and electrophilicity, epoxides are highly attractive building blocks for fundamental organic reactions. However, controlling the regioselectivity of disubstituted epoxide transformations is often particularly challenging. Most Lewis acid-mediated processes take advantage of intrinsic steric or electronic substrate bias to influence the site of nucleophilic attack. Therefore, the scope of many of these systems is frequently quite limited. Recent efforts to generate catalysts that can overcome substrate bias have expanded the synthetic utility of these well-known reactions. In this Perspective, we highlight various regioselective transformations of disubstituted epoxides, emphasizing those that have inspired the production of challenging, catalyst-controlled processes.

β-Hydroxy sulfides and their syntheses

Sulfur-containing natural products are ubiquitous in nature, their most abundant source being marine organisms since sulfur, in the form of the sulfate ion, is the second most abundant anion in sea water after chloride. As part of natural products, sulfur can appear in a multitude of combinations and oxidation states: thiol, sulfide (acyclic or heterocyclic), disulfide, sulfoxide, sulfonate, thioaminal, hemithioacetal, various thioesters, thiocarbamate and isothiocyanate. This review article focuses on β-hydroxy sulfides and analogs; their presence in natural products, general protocols for their synthesis, and examples of their application in target oriented synthesis.

Anion-dependent thermo-responsive supramolecular superstructures of Cu(ii) macrocycles

A heteroditopic ligand predominantly self-assembled into a dinuclear Cu(ii) macrocycle with various Cu²⁺ salts. However, each macrocycle is further hierarchically assembled to distinct supramolecular superstructures, where the shape of the morphology is found to be highly dependent on the counter-anions and temperature.

Nucleophilic ring opening of trans-2,3-disubstituted epoxides to β-amino alcohols with catalyst-controlled regioselectivity

We report the nucleophilic ring opening of unsymmetrical trans-epoxides to β-amino alcohols with catalyst-controlled regioselectivity.

Copper based coordination polymers based on metalloligands: utilization as heterogeneous oxidation catalysts

This work presents two copper-based coordination polymers and their utilization as stable, reusable and heterogeneous catalysts for the epoxidation of olefins using O₂ and for peroxide-mediated oxidation of benzyl alcohols under solvent-free conditions.

A metalloligand appended with benzimidazole rings: tetranuclear [CoZn3] and [CoCd3] complexes and their catalytic applications

A novel Co³⁺-based metalloligand, offering appended benzimidazole rings, has been utilized for the synthesis of catalytically active tetranuclear [CoZn₃] and [CoCd₃] heterometallic coordination complexes.

Carbon-sulphur cross coupling reactions catalyzed by nickel-based coordination polymers based on metalloligands

This work illustrates two Ni²⁺based coordination polymers and their utilization as reusable and heterogeneous catalysts for the C–S cross coupling reactions between assorted aromatic halides with thiophenol, cyclohexanethiol and ethanethiol.

Synthesis, characterization and properties of lanthanide coordination polymers with 3,5-bis(4-carboxyphenylmethyloxy) benzoic acid

Two types of lanthanide coordination polymers based on 3,5-bis(4-carboxyphenylmethyloxy) benzoic acid were synthesized under similar experimental conditions.