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The isolation of catenated nitrogen compounds is difficult, in part because these chains can readily lose nitrogen, creating a strong thermodynamic push towards decomposition. Now, a series of molecules containing radical anions of four-atom nitrogen chains have been synthesized and studied under ambient conditions; the chain can cleave into N1 and N3 fragments, and can act as a source of nitrene radical anion.

Substituted bicyclo[2.1.1]hexanes (BCHs) are emerging bicyclic hydrocarbon bioisosteres for ortho- and meta-substituted benzenes, but are difficult to access. Now a SmI₂-catalysed intermolecular coupling of bicyclo[1.1.0]butyl ketones and alkenes provides a general approach to access substituted BCHs, thus promoting their widespread use in medicinal chemistry and crop science.

The reasons for which many low-coordinate complexes exhibit bent geometry, rather than a higher symmetry, are still under debate. Here, the authors use high-pressure crystallography to examine whether low-coordinate f-block molecules become more planar or pyramidal under pressure; which happens is dictated by the dipole moment of the complex and the volume of the planar form.

The chemistry of group 13 metals (M) is dominated by +1 and +3 oxidation states, so MX₂ species are typically metal–metal-bonded dimers, M(II)₂X₄ or mixed-valence species M(I)M(III)X₄. Now, monomeric M(II)(boryl)₂ radicals have been prepared for gallium, indium and thallium. The compounds — structurally characterized by X-ray crystallography — are stable up to 130 °C and exhibit dominant metal-centred radical character.

Superatoms are metal clusters that collectively behave like an atom, but they usually require metal–metal bonding and thus they are based on main group or transition metals. Now it has been shown that trithorium nanoclusters with delocalized three-centre-one-electron thorium–thorium bonding exhibit exalted diamagnetism. This unveils actinide superatoms that exhibit open-shell jellium aromaticity.

In actinide chemistry, a longstanding bonding model describes metal-ligand binding using 6d-orbitals, with the 5f-orbitals remaining non-bonding. Here the authors explore the inverse-trans-influence — a case where the model breaks down — finding that the f-orbitals play a crucial role in dictating a trans-ligand-directed geometry.

The properties of actinide complexes depend on the ionic versus covalent nature of the bonds. Here, the authors report that pressure can distort actinide-oxygen bonding; differences seen for Th, U and Np result from the decreasing size of the atoms.

A crystalline cluster exhibits thorium–thorium bonding, adding to our knowledge of actinide–actinide bonding.

We describe recent advances in the understanding of covalency in the f element–other element bond through the synergistic application of computational quantum chemistry with nuclear magnetic resonance and X-ray spectroscopies.

Determining the covalency of actinide chemical bonding is a fundamentally important challenge. Here, the authors report a ¹⁵N nuclear magnetic resonance spectroscopy study of a terminal uranium-nitride, revealing exceptional NMR properties and covalency that redefine ¹⁵N NMR parameter space and actinide chemical bonding.

Photoinduced electron transfer through, and between, pyrrole moieties is an important process both in the natural world and emerging technologies. Here, the authors use both experiment and theoretical calculation to investigate a previously undiscovered relaxation pathway arising in pyrrole dimers.

In coordination and organometallic chemistry, back-bonding between an electron-rich, typically mid- or low-oxidation-state d-block metal centre and a ligand with accepting π* orbitals is widespread. Now, such an interaction has been observed between unlikely partners—high-oxidation-state uranium(v) 5f¹ ion and the poor π-acceptor ligand dinitrogen—in a U(v)–bis(imido)–N₂ complex stabilized by a lithium counterion.

Probing the chemistry of transuranic elements is notoriously challenging. Now, three neptunium(III) organometallic sandwich complexes have been prepared using a flexible macrocycle as ligand, and their molecular and electronic structures characterized, adding to our understanding of the behaviour of f-elements and suggesting that the lower oxidation state Np(II) may be chemically accessible.