Aromaticity is a cornerstone concept in chemistry, playing a crucial role in understanding molecular stability and reactivity. Traditionally, aromaticity has been primarily associated with cyclic planar conjugated organic molecules composed solely of carbon, but it has recently expanded to include metal-containing systems. However, metal-only aromatics remain extremely scarce. Here, we present the first neutral all-metal aromatic cluster with a rhombic geometry.

Nitroso compounds, R-N═O, containing N═O double bonds are ubiquitous and widely utilized in organic synthesis. In contrast, heavier congeners of nitroso compounds, namely pnictinidene chalcogenides R-Pn = E (Pn = P, As, Sb, Bi; E = O, S, Se, Te), are highly reactive and scarce. They have been stabilized in the coordination sphere of Lewis acid/base or by pronounced contribution from resonance structures, whereas free species with unperturbed pnictogen-chalcogen double bonds remains elusive.

Tetraphenylethylene (TPE) is a prototype aggregate-induced emission molecule. TPE-based conjugated macrocycles exhibit unique optical properties due to their peculiar cyclic topology. Because the symmetry of macrocycles strongly affects their photophysical properties, here we report a single-molecule study of the structures and orbitals of two TPE-based macrocycles of (C26H18)4 and (C26H18)6. Using scanning tunneling microscopy and spectroscopy, we discover that both macrocycles undergo spontaneous symmetry breaking in their conformations and frontier orbitals.

The activation of C–F bonds has long been regarded as the subject of research in organometallic chemistry, given their synthetic relevance and the fact that fluorine is the most abundant halogen in the Earth’s crust. However, C–F bond activation remains a largely unsolved challenge due to the high bond dissociation energies, which was historically dominated by transition metal complexes. Main group elements that can cleave unactivated monofluorobenzene are still quite rare and restricted to s-block complexes with a biphilic nature.

Tuning the spin state of metal carbynes, which have broad applications in organic synthesis and material science, presents a formidable challenge for modern chemists as the strong field nature of carbyne ligands dictates low-spin ground spin states (S = 0 or 1/2) for known metal carbynes. Through the oxidative addition reaction of a low-coordinate iron(0) N-heterocyclic carbene complex with the C−S bond of a thioazole-2-ylidene, we synthesized the first triplet (S = 1) metal terminal carbyne, an iron cyclic carbyne complex.

The synthesis, structures, and reactivity of the first neutral 2π-aromatic Si4 rings [LSiSiAr(X)]2 (3: X = Br; 4: X = Cl; L = PhC(NtBu)2, Ar = 2,4,6-Me3C6H2) were described. Compounds 3 and 4 were obtained by 1,3-halogenation of tetrasilacyclobutadiene (LSiSiAr)2 (2), which was prepared by the reductive cross-coupling of trisilane (ArSiCl2)2SiHAr with two equiv of chlorosilylene LSiCl.

For a long time, planar tetracoordinate carbon (ptC) represented an exotic coordination mode in organic and organometallic chemistry, but it is now a useful synthetic building block. In contrast, realization of planar tetracoordinate silicon (ptSi), a heavier analogue of ptC, is still challenging. Herein we report the successful synthesis and unusual reactivity of the first ptSi species of divalent silicon present in 3, supported by the chelating bis(N-heterocyclic silylene)bipyridine ligand, 2,2′-{[(4-tBuPh)C(NtBu)]2SiNMe}2(C5N)2, 1].

The synthesis of well-defined nanocarbon multilayers, beyond the bilayer structure, is still a challenging goal. Herein, two trilayer nanographenes were synthesized by covalently linking nanographene layers through helicene bridges. The structural characterization of the trilayer nanographenes revealed a compact trilayer-stacked architecture.

The reactions of chlorogermylene MsFluindtBu-GeCl 1, supported by a sterically encumbered hydrindacene ligand MsFluindtBu, with NaPCO(dioxane)2.5 and NaAsCO(18-c-6) in the presence of trimethylphosphine afforded trimethylphosphine-stabilized germylidenyl-phosphinidene 2 and -arsinidene 3, respectively. Structural and computational investigations reveal that the Ge–E′ bond (E′ = P and As) features a multiple-bond character.

As a fundamental chemical property, aromaticity guides the synthesis of novel structures and materials. Replacing the carbon moieties of aromatic hydrocarbons with transition metal fragments is a promising strategy to synthesize intriguing organometallic counterparts with a similar aromaticity to their organic parents. However, since antiaromaticity will endow compound instability, it is a great challenge to obtain an antiaromatic organometallic counterpart based on such transition metal replacement in aromatic hydrocarbons.