GA: We here report the first perarylated 2,3-diboratabutadiene dianion and its reaction with Cp2MCl2 (M = Zr, Hf) to afford unprecedented 2,3-diboratabutadiene π-complexes with unique coordination modes. Addition of an N-heterocyclic carbene (NHC) to the complexes gives rise to the donor-induced oxidation of the BB bond, resulting in two separate NHC-coordinated methyleneboranes and the liberation of transient metal(II) fragments “MCp2”.

Metal complexes of conjugated olefins have been known for a century. The formal heterosubstitution of carbon atoms in such ligands significantly alters their electronic properties. While several examples with terminal boron centers are known, butadiene transition metal complexes with internal BB bonds and thus bora-substitution in 2,3-position remain elusive. Herein, the first peraryl 2,3-diboratabutadiene dianion is reported, prepared in two steps as its lithium salt from readily available 1,2-dichloro-1,2-diduryldiborane(4) (duryl = 2,3,5,6-tetramethylphenyl). The reactions with Cp2MCl2 (M = Zr, Hf) afford unprecedented 2,3-diboratabutadiene π-complexes with unique coordination modes in between the familiar s-cis and s-trans conformations of the corresponding all-carbon derivatives. Addition of the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene (IMe) to the complexes gives rise to the donor-induced oxidation of the BB bond, resulting in two separate IMe-coordinated methyleneboranes with BC double bonds and the liberation of transient metal(II) fragments “MCp2”. At longer reaction times, the methyleneboranes are hydrogenated by the active “MCp2” species as evidenced by isolation of the corresponding saturated methyl borane adducts.

Novel amido-enaminone threads efficiently template the formation of hydrogen-bonded [2]rotaxanes and enable diverse postsynthetic modifications. Benzyl groups promote diastereoselective cyclizations to interlocked lactams while the enaminone motif allows stopper exchange while preserving the mechanical bond. One-pot cyclization and dethreading yield stereoselective, functionalized lactams with side-chain heterocycles.

Novel amido-enaminone threads serve as efficient templates for the assembly of hydrogen-bonded [2]rotaxanes, enabling versatile postsynthetic modifications. Benzyl groups on the amido moiety allow for diastereoselective intramolecular cyclizations, yielding interlocked β-lactams. The enaminone motif makes possible the stopper exchange while preserving the mechanical bond. Combining cyclization with one-pot stopper exchange and dethreading enables the stereoselective synthesis of highly functionalized noninterlocked lactams featuring a second heterocycle at their side chain via reactions with hydrazines or hydroxylamine.

GA: Sulfonimidoyl fluorides react with a diverse set of amines in a HOBt-catalyzed sulfur(VI) fluorine exchange reaction to access sulfonimidamides, including directly NH-sulfonimidamides, and in an automated workflow. In addition, SNAr reactivity of 4-fluoroaryl sulfonimidoyl fluorides is discovered and exploited to prepare complex sulfonimidoyl fluorides.

Sulfonimidamides have emerged as attractive chemical motifs in drug discovery and as sulfonamide bioisosteres that can offer improved pharmacokinetic and physiochemical properties. Herein, a mild sulfur(VI) fluorine exchange (SuFEx) reaction of sulfonimidoyl fluorides using HOBt as a nucleophilic catalyst is reported that is applicable to automated array technologies. A diverse set of sulfonimidamides is prepared with functionalized amines and sulfonimidoyl fluorides, with variation in carbon and nitrogen-substituents. Moreover, the discovery and utilization of SNAr reactivity of a fluoroaryl-sulfonimidoyl fluoride under modified conditions, occurring in the presence of the sulfonimidoyl fluoride functionality, allow for the divergent generation of sulfonimidoyl fluoride reagents. Orthogonal SNAr or SuFEx processes are achieved highly chemoselectively, as well as sequentially in one-pot. A further 24-compound array is generated using an automated reaction set-up and purification.

Dysprosium in high-symmetry environment: an original crystal-field energetic profile provides an experimental demonstration of the oblate/prolate theory and is also responsible for an unprecedented orange-to-red emission.

The importance of investigating high-symmetry systems in order to reveal properties that would otherwise be concealed in less symmetrical compounds is demonstrated. This is particularly true for discrete coordination complexes that tend to adopt low symmetries. The magnetic, optical, and theoretical investigation of [Dy{N(SiMe3)2}3], an amido complex that features an almost trigonal electrostatic environment around the DyIII ion, is reported here. While this specific coordination is ideally suited to the stabilization of high magnetic ground state for “prolate” YbIII-based single-molecule magnet (SMM), it is the opposite for oblate DyIII. Hence, [Dy{N(SiMe3)2}3] is expected to display the lowest conceivable magnetic anisotropy. This is confirmed herein by magneto-optical and theoretical correlations. An extremely pure Kramers doublet composition is observed on a totally reversed energetic profile compared to the standard DyIII-SMM. This results in a paramagnetic but dynamically silent compound, even when an external dc field is applied. Additionally, this unusual energetic profile induces an exceptional optical signature, with orange (300 K) to red (4 K) emission, far from the traditional white-to-yellow emission expected for a DyIII ion.

The nitrone moiety's versatility in covalent organic polymer (COP) materials is shown by its ability to form either nitrone-linked or oxime O-ether-linked COPs from the same building blocks, simply by changing reaction conditions. Additionally, its 1,3-dipolar cycloaddition reactivity enabled the synthesis of a functionalized isoxazolidine-linked polymer via phenylvinylsulfone addition during polymer formation.

The development of novel covalent organic polymers (COPs) incorporating nitrone linkages and their chemical transformation into new materials through tandem reactions is reported. Using 1,3,5-tris(4-hydroxyaminophenyl)triazine and terephthaldehyde as building blocks, a nitrone-linked COP was synthesized under mild conditions. The inherent versatility of the nitrone moiety enabled the formation of oxime O-ether-linked COPs through simple thermal treatment of the same monomers. Additionally, making use of the well-known 1,3-dipolar cycloaddition reaction with nitrones, a multicomponent transformation with phenylvinylsulfone led to the formation of a new isoxazolidine-linked polymer. Structural and chemical characterizations using FT-IR, 13C and 15N CP-MAS NMR, XPS, and scanning electron microsopy (SEM) confirmed the successful formation of the polymeric materials and the direct nitrone conversion into different groups and moieties. These results demonstrate the versatility of nitrone linkages for creating diverse COPs and expand the toolbox for designing functional organic materials.

Using density functional theory calculations, and by comparing calculated gas-phase formation energies, bulk cohesive energies, lattice constants, and nitrogen and ammonia adsorption energies on Fe and Fe-nitride surfaces to experimental estimates, the accuracy of several XC functionals is assessed for modeling iron-catalyzed ammonia synthesis.

Density functional theory (DFT) has been widely employed for elucidating mechanistic aspects of heterogeneous catalysis. However, the accuracy of DFT calculations relies heavily on selecting an exchange-correlation (XC) functional that correctly describes the electronic structure of materials involved in the reactions. This study assesses the accuracy of several XC density functionals for modeling the iron-catalyzed ammonia synthesis system. In the assessment of functional accuracy, experimental references are compared to DFT-calculated values for the formation energy of gas-phase ammonia and nitrogen, bulk Fe/Fe-nitride (γ′-Fe4N) lattice constants and cohesive/formation energies, and nitrogen and ammonia binding energies on Fe(100), Fe(111), Fe(110), and γ′-Fe4N(111). It is observed that the experimental value for each of these descriptors is accurately modeled by at least one functional. RPBE alone provides reliable estimates for both the lattice constant and cohesive energy of Fe and γ′-Fe4N. Temperature-programmed desorption experiments led to estimates for N and NH3 adsorption across several Fe-based facets that are best captured by RPBE. These results highlight the importance of choosing an appropriate XC functional that accurately describes experimental systems and offer insights into effectively modeling the interactions between nitrogen and ammonia on Fe-based surfaces.

A double-concave radical cation salt, octadecamethoxyhexabenzocoronenium hexafluoroantimonate, is capable of encapsulating two hexafluorobenzene molecules in the solid state. The complex exhibits long-wavelength absorption beyond the NIR region. Furthermore, its photophysical and magnetic properties are modulated by the presence or absence of the guest hexafluorobenzene molecules.

Herein, a nonplanar radical cation salt is successfully synthesized and isolated comprising the octadecamethoxyhexabenzocoronene radical cation, a large fused polycyclic π-electron system, with hexafluoroantimonate ion as the counterion. X-ray crystal structure analysis reveals a double-concave structure with two hexafluorobenzene molecules incorporated as guest species. Natural energy decomposition analysis indicates that charge transfer interactions predominantly stabilize the complex between the radical cation and hexafluorobenzene. Interestingly, the presence or absence of hexafluorobenzene in the solid state affected the absorption properties in the near-infrared to infrared region and modulated the magnetic interactions between radical species.

The stereoretentive para-Claisen-Cope rearrangement enabled by Europium catalysis is presented, achieving precise phenol functionalization with exceptional chirality transfer under air- and moisture-tolerant conditions. A novel carbonate unlocks superior enantioselectivity in the Tsuji-Trost allylic alkylation, paving the way for highly enantioenriched phenolic derivatives and new synthetic possibilities.

A stereoretentive para-Claisen-Cope rearrangement of chiral aryl-allyl ethers is reported, achieving near-perfect chirality transfer thereby furnishing products with exceptional enantiomeric excess (up to > 98% ee) as single regioisomers. This transformation is operationally simple, air- and moisture-tolerant, and catalyzed by a commercially available Europium (III) complex. Mechanistic studies suggest that this para-Claisen-Cope process involves two consecutive [3,3]-sigmatropic rearrangements, resulting in overall retention of stereochemistry. Furthermore, an optimized asymmetric allylic alkylation protocol enables the straightforward preparation of enantioenriched aryl-allyl ether substrates with high enantiomeric purity. Both transformations exhibit broad functional group tolerance, affording the desired products in good to excellent yields.

A convenient and practical method for the clean generation of alkyl–λ3–iodanes is reported using tetraalkylsilanes and iodine tris(trifluoroacetate). An in situ-generated methyl–λ3–iodane works as a soft and highly electrophilic methylation reagent, which enables methylation of tertiary sulfonamides at low temperatures and following transamidation and fluorination reactions.

Hypervalent iodine compounds have found various applications in organic chemistry and related research fields. Compared with aryl-, alkynyl-, and alkenyl-substituted iodanes and iodonium salts, alkyl–λ3–iodanes have been much less studied due to their infamous instability and the lack of convenient methods for their generation. Herein, it is reported that the reaction between a tetraalkylsilane and iodine tris(trifluoroacetate) at low temperature cleanly generates the corresponding alkyl–λ3–iodane in commonly used chlorinated solvents. The in situ-generated alkyl–λ3–iodanes are reasonably stable at low temperature, and Me–λ3–iodane serves as a soft and highly electrophilic methylating agent for tertiary sulfonamides. This alkylative activation of tertiary sulfonamides provides reactive sulfonyl ammonium intermediates that can achieve transamidation and fluorination reactions, thus demonstrating the synthetic utility of the in situ-generated alkyl–λ3–iodane.

[(Cp)FeII(naphthalene)](PF6) catalysts are reported with improved curing efficiency of alkyd paints compared to [(Cp)FeII(arene)](PF6), particularly in dark-pigmented formulations. Their improved photosensitivity enables faster drying at lower concentrations, presenting a promising alternative to conventional industrial driers under regulatory pressure. The photoactivatable iron driers are effective in challenging pigmented systems—such as blue and black paints—where light penetration is typically limited.

The class of photoactive complexes [(Cp)FeII(arene)]+ (Cp = cyclopentadienyl, arene = C6H6, C6H5;Me) enable light-controlled alkyd paint curing, eliminating the need for anti-skinning agents. While [(Cp)FeII(benzene)](PF6) (0.10 wt%) initiates curing under ambient light (116 Lux/1.7 mW/m2) within 6 h for transparent paints, it is ineffective in dark-colored formulations. Here, we demonstrate that the more photosensitive complexes [(Cp)FeII(L)](PF6) (L = naphthalene, 5-methoxynaphthalene, 6-methoxy-naphthalene, 5,8-dimethoxynaphthalene) accelerate curing with lower loadings (0.05 wt%). Due to their higher extinction coefficients and red-shifted adsorption bands, these [(Cp)FeII(L)](PF6) catalysts effectively cure dark-pigmented paints. Mössbauer spectroscopy reveals the formation of a high-spin FeII intermediate as the active species. TD-DFT calculations reveal a redshift in absorption, attributed to a transition from dz[ 2 ]-d xy*/d yz* (arene/naphthalene) to Lπ-d xy*/d yz* (methoxylated naphthalenes). Excitation of the complexes using wavelengths corresponding to these absorbance bands result in weakening of the FeII-η6C6 bonds, facilitating light-induced dissociation. This advancement enhances latency originating from photoactivation while expanding applicability to pigmented systems.