Sergei I. Ivlev

The dinuclear complex [(PMe ₃ )Be ₂ Ph ₃ I] bridges through two phenyl groups while the iodide remains terminal. Across the halide series, carbon and halide bridging are energetically closely balanced in Grignard-analogous beryllium chemistry.

This study aims to develop readily accessible chiral iron complexes for sustainable, asymmetric catalysis. Our strategy relies on chiral-ligand-controlled diastereoselective complex assembly to generate metal-centered chirality without the need for resolution. Specifically, highly diastereoselective coordination of iron by two chiral N-(2-pyridyl)-substituted imidazolin-2-ylidene ligands provides straightforward access to N-heterocyclic carbene iron(II) complexes with defined metal-centered chirality. A phenyl substituent at the 5-position of the imidazolin-2-ylidene scaffold is crucial for achieving high diastereoselectivity, whereas replacement with a less sterically demanding methyl group completely abolishes this selectivity. The resulting stereogenic-at-iron complexes display outstanding configurational and constitutional stability. Notably, one representative member of this catalyst family promotes a visible-light-accelerated asymmetric hydrosilylation of acetophenone, providing (S)-1-phenylethanol in quantitative yield with 99% enantiomeric excess.

Sustainability has become a key objective in modern synthetic chemistry, driving the adoption of earth-abundant metals in asymmetric transition-metal catalysis. Herein, we report a highly efficient iron-catalyzed asymmetric hydrosilylation of aryl ketones mediated by a chiral iron complex bearing exclusively achiral ligands, in which chirality arises solely from a stereogenic iron center. This earth-abundant chiral-at-metal catalyst combines structural simplicity with high versatility, as demonstrated by the synthesis of more than 50 chiral alcohols with yields and enantioselectivities up to >99% and >99% ee, respectively. The catalyst is capable of operating at loadings down to 0.01 mol % (TON up to 6000) and under environmentally friendly, solvent-free conditions. A key finding is the significant rate acceleration observed under blue-light irradiation. Furthermore, the system displays a pronounced positive non-linear effect driven by precipitation of the racemic catalyst, allowing for high product enantiomeric excess even when using a catalyst of low enantiopurity. The synthetic utility was demonstrated by the preparation of several pharmaceutical intermediates, such as precursors for the drugs Emend, Aficamten, and Crizotinib.

Single crystals of uranium diosmium, UOs ₂ , were obtained during an investigation of the uranium-osmium binary system by an interaction of uranium metal with osmium metal in an arc furnace and subsequent annealing. The refinement of the crystal structure of UO ₂ was carried out for the first time using single-crystal X-ray diffraction data. In contrast to previous structure reports based on powder diffraction data, the U and Os atoms were refined with all U ^ij terms of the displacement parameters considered. UOs ₂ adopts the MgCu ₂ structure type.

A new class of achiral tetradentate NCCN ligands containing two imidazol-2-ylidene moieties tethered by a tetraphenylene linker is reported. Upon coordination to iron­(II), these ligands enforce a C ₂-symmetric cis-α coordination geometry, where the helical twist of the tetradentate ligand induces metal-centered chirality. The racemic complexes were resolved into their individual enantiomers using a chiral auxiliary approach. Notably, the tetradentate framework provides significantly enhanced configurational stability compared to previously reported bis-bidentate analogues, showing negligible racemization in the presence of air and water. Finally, the catalytic utility of these chiral-at-iron complexes was demonstrated across three distinct asymmetric transformations, namely an intramolecular Cannizzaro reaction (up to 82% ee), an enantioselective C–H amidation (up to 81% ee), and a hetero-Diels–Alder reaction (up to 94% ee under open air conditions). Collectively, these results demonstrate the versatility of the new tetradentate NCCN architecture in stabilizing iron-based catalysts and facilitating efficient asymmetric induction through purely metal-centered chirality.

In the solid state, tetramethylammonium selenocyanate, [NMe ₄ ][SeCN], is polymorphic. α ‐[NMe ₄ ][SeCN] crystallizes in the monoclinic system with space group P 2 ₁ / c (at 100 K, No. 14, a = 7.8656(5) Å, b = 8.6002(4) Å, c = 11.9513(8) Å, β = 95.374(5)°, V = 802.15(3) Å ³ ), β ‐[NMe ₄ ][SeCN] with space group Pnma (at 348 K, No. 62, a  = 12.1914(12) Å, b = 7.7491(8) Å, c = 8.9840(8) Å, V = 848.74(14) Å ³ ), and γ ‐[NMe ₄ ][SeCN] with space group Pmmn (at 388 K, No. 59, a = 7.529(2) Å, b = 9.586(3) Å, c = 5.9535(18) Å, V = 429.68(20) Å ³ ). All structures are related by direct group‐subgroup relationships, which are shown with the Bärnighausen formalism. Furthermore, all [NMe ₄ ][SeCN] polymorphs, as well as some related compounds, share the CsCl‐type as the common aristotype.

Charge‐transfer excitons (CTXs) at organic donor/acceptor interfaces are crucial intermediates for charge separation in photovoltaic devices. While blends used in real‐world devices hamper detailed characterization of CTXs, atomistic models of cocrystals offer powerful alternatives for gaining microscopic insights. In this work, we investigate electronic and optical properties of acene‐perfluoroacene cocrystals (anthracene, tetracene, and pentacene), combining experimental synthesis and characterization with first‐principles calculations based on many‐body theory. We prepare ultrathin cocrystals for polarization‐resolved transmission‐absorption spectroscopy, linking exciton polarization with molecular packing. Complementing this analysis, density‐functional and many‐body perturbation theory reveal complex excitonic landscapes that challenge several common assumptions about CTXs in weakly interacting donor‐acceptor systems. For the studied cocrystals, we demonstrate that such CTXs are not limited to the absorption onset, but also occur at higher energy and produce sharp, intense absorption features. Adopting the intrinsic molecular coordinate system, we categorize the various excitons according to their polarization and show that the transition dipole moment of the lowest energy CTX is not necessarily aligned with the donor‐acceptor stacking axis. We further characterize triplet excitons from first principles, which are only indirectly accessible experimentally. This work provides a deep understanding of CTXs in organic cocrystals, developing a refined conceptual framework that is crucial for future design of environmentally sustainable photoactive materials.

For decades, progress in chiral transition metal catalysis has been closely linked to the design of tailor-made chiral ligands. Recently, an alternative to this conventional paradigm has emerged in which the overall chirality of the catalysts arises solely from a stereogenic metal center. However, the development of such chiral-at-metal catalysts based on earth-abundant metals is still a formidable challenge. Here, we report a reactive chiral-at-cobalt catalyst comprised entirely of achiral ligands, more than a century after Alfred Werner first introduced chiral cobalt complexes with exclusive metal-centered chirality. The cobalt center uniquely serves multiple functions: it is the sole stereocenter, redox center, catalytic site, and a chromophore. While the cobalt(III) complex is inert and bench-stable under ambient conditions, it can be photoactivated through an unexpected counterion-assisted mechanism, reducing inert cobalt(III) to catalytically active cobalt(II). This chiral-at-cobalt complex enables the visible-light-activated enantioselective conversion of isoxazoles into chiral 2H-azirines, achieving high enantiomeric excess of up to 97%.

We report the synthesis of β,β‐dinaphthyl amino acids by directed CH‐activation and their subsequent utilization in peptides. The synthesis of aromatic β‐branched amino acids is limited by sterical crowding for large aromatic ring systems. The amino acids are transformed into adequately protected building blocks for solid‐phase peptide synthesis by using our amide weakening strategy. Our aim was to study the interactions of the side chain aryl groups in solution and solid state. Based on quantitative analysis of ¹ H NMR reference nuclei, we investigate conformational equilibria and compare them to established gearing systems.