Recent Developments in the Preparation and Chemistry of Metallacycles and Metallacages via Coordination

The Engineering and Physical Sciences Research Council and the European Research Council are acknowledged for financial support.

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Stimuli-Responsive Metal–Ligand Assemblies

ConspectusMetal–organic frameworks (MOFs) are periodic, hybrid, atomically well-defined porous materials that typically form by self-assembly and consist of inorganic nodes (metal ions or clusters) and multitopic organic linkers. MOFs as a whole offer many intriguing properties, including ultrahigh porosity, tunable chemical functionality, and low density. These properties point to numerous potential applications, including gas storage, chemical separations, catalysis, light harvesting, and chemical sensing, to name a few. Reticular chemistry, or the linking of molecular building blocks into predetermined network structures, has been employed to synthesize thousands of MOFs. Given the vast library of candidate nodes and linkers, the number of potentially synthetically accessible MOFs is enormous. Nevertheless, a powerful complementary approach to obtain specific structures with desired chemical functionality is to modify known MOFs after synthesis. This approach is particularly useful when incorporation o...

Postsynthetic Tuning of Metal–Organic Frameworks for Targeted Applications

Metal-organic frameworks (MOFs) are a class of distinctive porous crystalline materials constructed by metal ions/clusters and organic linkers. Owing to their structural diversity, functional adjustability, and high surface area, different types of MOF-based single metal sites are well exploited, including coordinately unsaturated metal sites from metal nodes and metallolinkers, as well as active metal species immobilized to MOFs. Furthermore, controllable thermal transformation of MOFs can upgrade them to nanomaterials functionalized with active single-atom catalysts (SACs). These unique features of MOFs and their derivatives enable them to serve as a highly versatile platform for catalysis, which has actually been becoming a rapidly developing interdisciplinary research area. In this review, we overview the recent developments of catalysis at single metal sites in MOF-based materials with emphasis on their structures and applications for thermocatalysis, electrocatalysis, and photocatalysis. We also compare the results and summarize the major insights gained from the works in this review, providing the challenges and prospects in this emerging field.

Metal-Organic Framework-Based Catalysts with Single Metal Sites.

More than a quarter of a century after the first metal template synthesis of a [2]catenane in Strasbourg, there now exists a plethora of strategies available for the construction of mechanically bonded and entwined molecular level structures. Catenanes, rotaxanes, knots and Borromean rings have all been successfully accessed by methods in which metal ions play a pivotal role. Originally metal ions were used solely for their coordination chemistry; acting either to gather and position the building blocks such that subsequent reactions generated the interlocked products or by being an integral part of the rings or "stoppers" of the interlocked assembly. Recently the role of the metal has evolved to encompass catalysis: the metal ions not only organize the building blocks in an entwined or threaded arrangement but also actively promote the reaction that covalently captures the interlocked structure. This Review outlines the diverse strategies that currently exist for forming mechanically bonded molecular structures with metal ions and details the tactics that the chemist can utilize for creating cross-over points, maximizing the yield of interlocked over non-interlocked products, and the reactions-of-choice for the covalent capture of threaded and entwined intermediates.

Strategies and tactics for the metal-directed synthesis of rotaxanes, knots, catenanes, and higher order links.

Explosion Hazards of Sodium Hydride in Dimethyl Sulfoxide, N,N-Dimethylformamide, and N,N-Dimethylacetamide

An iridium pincer complex has been immobilised in the metal–organic framework NU-1000 using a technique called solvent assisted ligand-incorporation (SALI). The framework proved to be stable under the conditions required to activate the iridium complex and spectroscopic investigations showed formation of the catalytically active iridium dihydride. The Ir-pincer modified NU-1000 is an active catalyst for the condensed phase hydrogenation of a liquid alkene (1-decene and styrene) and shows enhanced activity with respect to a homogeneous analogue. Additionally, the Ir-pincer immobilised inside NU-1000 operated as an efficient heterogenous catalyst under flow conditions.

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A metal–organic framework immobilised iridium pincer complex

Pd3L2 metallo-cryptophane cages with cyclotriveratrylene-type L ligands can be stabilized by use of a bis-N-heterocyclic carbene as an auxiliary cis-protecting ligand, while use of more common protecting chelating ligands such as ethylenediamine saw a Pd3L2 to Pd6L8 rearrangement occur in solution. The crystalline Pd3L2 complexes act as sponges, taking up 1,2-dichorobenzene or iodine in a single-crystal-to-single-crystal fashion despite not exhibiting conventional porosity.

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Metallo-cryptophanes decorated with bis-N-heterocyclic carbene ligands: self-assembly and guest uptake into a nonporous crystalline lattice.

https://pubs.rsc.org/en/content/articlepdf/2015/cc/c5cc03071d

James J. Henkelis

Papers

Explosion Hazards of Sodium Hydride in Dimethyl Sulfoxide, N,N-Dimethylformamide, and N,N-Dimethylacetamide

A metal–organic framework immobilised iridium pincer complex

Metallo-cryptophanes decorated with bis-N-heterocyclic carbene ligands: self-assembly and guest uptake into a nonporous crystalline lattice.

Controlling the assembly of cyclotriveratrylene-derived coordination cages

M3L2 metallo-cryptophanes: [2]catenane and simple cages