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Versatile, efficient and robust (pre)catalysts are pivotal in accelerating the discovery and optimization of chemical reactions, shaping diverse synthetic fields such as cross-coupling, C-H functionalization and polymer chemistry. Yet, their scarcity in certain domains has hindered the advancement and adoption of new applications. Here we present a highly reactive air- and moisture-stable ruthenium precatalyst [( t BuCN) 5 Ru(H 2 O)](BF 4 ) 2 , featuring a key exchangeable water ligand. This versatile precatalyst drives an array of transformations, including late-stage C(sp 2 )-H arylation, primary/secondary alkylation, methylation, hydrogen/deuterium exchange, C(sp 3 )-H oxidation, alkene isomerization and oxidative cleavage, consistently outperforming conventionally used ruthenium (pre)catalysts. The generality and applicability of this precatalyst is exemplified through the potential for rapid screening and optimization of photocatalytic reactions with a suite of in situ generated ruthenium photocatalysts containing hitherto unknown complexes, and through the rapid discovery of reactivities previously unreported for ruthenium. The diverse applicability observed is suggestive of a generic platform for reaction simplification and accelerated synthetic discovery that will enable broader applicability and accessibility to state-of-the-art ruthenium catalysis., (© 2024. The Author(s).)

A core feature of covalent organic frameworks (COFs) is crystallinity, but current crystallization processes rely substantially on trial and error, chemical intuition and large-scale screening, which typically require harsh conditions and low levels of supersaturation, hampering the controlled synthesis of single-crystal COFs, particularly on large scales. Here we report a strategy to produce single-crystal imine-linked COFs in aqueous solutions under ambient conditions using amphiphilic amino-acid derivatives with long hydrophobic chains. We propose that these amphiphilic molecules self-assemble into micelles that serve as dynamic barriers to separate monomers in aqueous solution (nodes) and hydrophobic compartments of the micelles (linkers), thereby regulating the polymerization and crystallization processes. Disordered polyimines were obtained in the micelle, which were then converted into crystals in a step-by-step fashion. Five different three-dimensional COFs and a two-dimensional COF were obtained as single crystals on the gram scale, with yields of 92% and above., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

A fundamental bonding model in coordination and organometallic chemistry is the synergic, donor-acceptor interaction between a metal and a neutral π-acceptor ligand, in which the ligand σ donates to the metal, which π back-bonds to the ligand. This interaction typically involves a metal with an electron-rich, mid-, low- or even negative oxidation state and a ligand with a π* orbital. Here, we report that treatment of a uranium-carbene complex with an organoazide produces a uranium(V)-bis(imido)-dinitrogen complex, stabilized by a lithium counterion. This complex, which was isolated in a crystalline form, involves an electron-poor, high-oxidation-state uranium(V) 5f 1 ion that is π back-bonded to the poor π-acceptor ligand dinitrogen. We propose that this is made possible by a combination of cooperative heterobimetallic uranium-lithium effects and the presence of suitable ancillary ligands that render the uranium ion unusually electron rich. This electron-poor back-bonding could have implications for the field of dinitrogen activation.

The simultaneous synthesis of a molecular nine-crossing composite knot that contains three trefoil tangles of the same handedness and a [Formula: see text] link (a type of cyclic [3]catenane topologically constrained to always have at least three twists within the links) is reported. Both compounds contain high degrees of topological writhe (w = 9), a structural feature of supercoiled DNA. The entwined products are generated from the cyclization of a hexameric Fe(II) circular helicate by ring-closing olefin metathesis, with the mixture of topological isomers formed as a result of different ligand connectivity patterns. The metal-coordinated composite knot was isolated by crystallization, the topology unambiguously proven by tandem mass spectrometry, with X-ray crystallography confirming that the 324-atom loop crosses itself nine times with matching handedness (all Δ or all Λ) at every metal centre within each molecule. Controlling the connectivity of the ligand end groups on circular metal helicate scaffolds provides an effective synthetic strategy for the stereoselective synthesis of composite knots and other complex molecular topologies.

Biaryls are ubiquitous core structures in drugs, agrochemicals and organic materials that have profoundly improved many aspects of our society. Although traditional cross-couplings have made practical the synthesis of many biaryls, C-H arylation represents a more attractive and cost-effective strategy for building these structural motifs. Furthermore, the ability to install biaryl units in complex molecules via late-stage C-H arylation would allow access to valuable structural diversity, novel chemical space and intellectual property in only one step. However, known C-H arylation protocols are not suitable for substrates decorated with polar and delicate functionalities, which are commonly found in molecules that possess biological activity. Here we introduce a class of ruthenium catalysts that display a unique efficacy towards late-stage arylation of heavily functionalized substrates. The design and development of this class of catalysts was enabled by a mechanistic breakthrough on the Ru(II)-catalysed C-H arylation of N-chelating substrates with aryl (pseudo)halides, which has remained poorly understood for nearly two decades.