A Cationic Unsaturated Platinum(II) Complex that Promotes the Tautomerization of Acetylene to Vinylidene

Complex [PtMe₂(PMe₂Ar )] ( 1 ), which contains a tethered terphenyl phosphine (Ar =2,6‐(2,6‐ⁱ Pr₂C₆H₃)₂C₆H₃), reacts with [H(Et₂O)₂]BAr_F (BAr_F⁻=B[3,5‐(CF₃)₂C₆H₃]₄⁻) to give the solvent (S) complex [PtMe(S)(PMe₂Ar )]⁺ ( 2⋅S ). Although the solvent molecule is easily displaced by a Lewis base (e.g., CO or C₂H₄) to afford the corresponding adducts, treatment of 2⋅S with C₂H₂ yielded instead the allyl complex [Pt(η³‐C₃H₅)(PMe₂Ar )]⁺ ( 6 ) via the alkyne intermediate [PtMe(η²‐C₂H₂)(PMe₂Ar )]⁺ ( 5 ). Deuteration experiments with C₂D₂, and kinetic and theoretical investigations demonstrated that the conversion of 5 into 6 involves a Pt^II‐promoted HC≡CH to :C=CH₂ tautomerization in preference over acetylene migratory insertion into the Pt−Me bond.     

Confined Lewis Pairs: Investigation of the X−→Si20 Interaction in Halogen-Encapsulating Silafulleranes

A joint theoretical and experimental study on 32 endohedral silafullerane derivatives [X@Si₂₀Y₂₀]⁻ (X=F-I; Y=F-I, H, Me, Et) and -[Cl@Si₂₀H₁₂Y₈]⁻ (Y=F-I) is presented. First, we evaluated the structure-determining template effect of Cl⁻ in a systematic series of concave silapolyquinane model systems. Second, we investigated the X⁻→Si₂₀ interaction energy ( ) as a function of X⁻ and Y and found the largest values for electron-withdrawing exohedral substituents Y. Given that X⁻ ions can be considered as Lewis bases and empty Si₂₀Y₂₀ clusters as Lewis acids, we classify our inseparable host–guest complexes [X@Si₂₀Y₂₀]⁻ as “confined Lewis pairs”. Third, ³⁵Cl NMR spectroscopy proved to be highly diagnostic for an experimental assessment of the Cl⁻→Si₂₀ interaction as the paramagnetic shielding and, in turn, (³⁵Cl) of the endohedral Cl⁻ ion correlate inversely with . Finally, we disclose the synthesis of [PPN][Cl@Si₂₀Y₂₀] (Y=Me, Et, Br) and provide a thorough characterization of these new silafulleranes.     

Crossover between Tilt Families and Zero Area Thermal Expansion in Hybrid Prussian Blue Analogues

Materials in the family of Prussian blue analogues (C₃H₅N₂)₂K[ M (CN)₆], where C₃H₅N₂ is the imidazolium ion and M =Fe, Co, undergo two phase transitions with temperature; at low temperatures the imidazolium cations have an ordered configuration (C 2/c ), while in the intermediate‐ and high‐temperature phases (both previously reported as ) they are dynamically disordered. We show from high‐resolution powder neutron diffraction data that the high‐temperature phase has zero area thermal expansion in the ab ‐plane. Supported by Landau theory and single‐crystal X‐ray diffraction data, we re‐evaluate the space group symmetry of the intermediate‐temperature phase to . This reveals that the low‐to‐intermediate temperature transition is due to competition between two different tilt patterns of the [ M (CN)₆]³⁻ ions. Controlling the relative stabilities of these tilt patterns offers a potential means to tune the exploitable electric behaviour that arises from motion of the imidazolium guest.     

Synthesis and Structures of d10–d10 M2(μ‐dppm)2 Complexes with Sensitive Metal–Metal Distances in Response to the Binding of Sigma Donors

Diphosphine‐bridged dicopper(I) acetate complexes [Cu₂(μ‐dppm)₂(μ‐OAc)]X ( 2 X; X^? = , ) and [Cu₂(μ‐dppm)₂(μ‐OAc)(MeCN)]X ( 4 X) were prepared and the structures of 2 (PF₆ ) and 4 (PF₆ ) determined by X‐ray crystallography. The ground‐state geometries of [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ and [Cu₂(μ‐dppm)₂(μ‐OAc)(L)]⁺ (L = py, MeCN, THF, acetone, MeOH) were also obtained using density functional theory (DFT). The increased Cu – Cu distances found experimentally and theoretically by comparing the structures of cation [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ and its derivatives [Cu₂(μ‐dppm)₂(μ‐OAc)(L)]⁺ reflect the binding of various sigma donors (L). When using [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ as a structure sensor, the electron‐donating strength of a sigma donor can be quantitatively expressed as a DFT‐calculated Cu – Cu distance with the relative strength in the order py > MeCN > THF > acetone > MeOH, as determined.     

Terminal Iron Carbyne Complexes Derived from Arrested CO2 Reductive Disproportionation

The encumbered tetraisocyanide dianion Na₂[Fe(CNAr )₄] reacts with two molecules of CO₂ to effect reductive disproportionation to CO and carbonate ([CO₃]²⁻). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono‐CO₂ adduct. This results in the formation of four‐coordinate terminal iron carbynes possessing an aryl carbamate substituent owing to the direct attachment of an C(O)OSiR₃ group to an isocyanide nitrogen atom. Crystallographic, spectroscopic, and computational analyses of these iron–carbon multiply bonded species reveal electronic structure properties indicative of a conformationally locked iron carbyne unit.     

The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me,Ph, Et)

Multinuclear solid‐state NMR studies of Cp*₂Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition ⁴⁵Sc NMR spectra show that the quadrupolar coupling constants (C_q) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*₂Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH₂CH₃ is related to coupling between the filled σ_C‐C orbital and the vacant orbital.     

Electrocatalytic Synthesis of Ammonia at Room Temperature and Atmospheric Pressure from Water and Nitrogen on a Carbon‐Nanotube‐Based Electrocatalyst

Ammonia is synthesized directly from water and N₂ at room temperature and atmospheric pressure in a flow electrochemical cell operating in gas phase (half‐cell for the NH₃ synthesis). Iron supported on carbon nanotubes (CNTs) was used as the electrocatalyst in this half‐cell. A rate of ammonia formation of 2.2×10⁻³ g m⁻² h⁻¹ was obtained at room temperature and atmospheric pressure in a flow of N₂, with stable behavior for at least 60 h of reaction, under an applied potential of −2.0 V. This value is higher than the rate of ammonia formation obtained using noble metals (Ru/C) under comparable reaction conditions. Furthermore, hydrogen gas with a total Faraday efficiency as high as 95.1 % was obtained. Data also indicate that the active sites in NH₃ electrocatalytic synthesis may be associated to specific carbon sites formed at the interface between iron particles and CNT and able to activate N₂, making it more reactive towards hydrogenation.     

A T‐Shaped Nickel(I) Metalloradical Species

A T‐shaped Ni^I complex was synthesized using a rigid acridane‐based pincer ligand to prepare a metalloradical center. Structural data displays a nickel ion is embedded in the plane of a PNP ligand. Having a sterically exposed half‐filled orbital, this three‐coordinate Ni^I species reveals unique open‐shell reactivity including the homolytic cleavage of various σ‐bonds, such as H−H, N−N, and C−C.     

Combining Orthogonal Chain‐End Deprotections and Thiol–Maleimide Michael Coupling: Engineering Discrete Oligomers by an Iterative Growth Strategy

Orthogonal maleimide and thiol deprotections were combined with thiol–maleimide coupling to synthesize discrete oligomers/macromolecules on a gram scale with molecular weights up to 27.4 kDa (128mer, 7.9 g) using an iterative exponential growth strategy with a degree of polymerization (DP) of 2ⁿ −1. Using the same chemistry, a “readable” sequence‐defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated using sequential growth (DP=2ⁿ −1) or double exponential dendrimer growth approaches (DP=2 −1) with significantly accelerated growth rates. A versatile, efficient, and metal‐free method for construction of discrete oligomers with tailored structures and a high growth rate would greatly facilitate research into the structure–property relationships of sophisticated polymeric materials.     

A Ferroelectric Iron(II) Spin Crossover Material

A dual‐function material in which ferroelectricity and spin crossover coexist in the same temperature range has been obtained. Our synthetic strategy allows the construction of acentric crystal structures in a predictable way and is based on the high directionality of hydrogen bonds. The well‐known iron(II) spin crossover complex [Fe(bpp)₂]²⁺ (bpp=2,6‐bis(pyrazol‐3‐yl)pyridine), a four‐fold noncentrosymmetric H‐bond donor, was combined with a disymmetric H‐bond acceptor such as the isonicotinate (isonic) anion to afford [Fe(bpp)₂](isonic)₂⋅2 H₂O. This low‐spin iron(II) compound crystallizes in the acentric nonpolar I space group and shows piezoelectricity and SHG properties. Upon dehydration, it undergoes a single‐crystal to single‐crystal structural rearrangement to a monoclinic polar Pc phase that is ferroelectric and exhibits spin crossover.     

(111) Facet-oriented Cu2Mg Intermetallic Compound with Cu3-Mg Sites for CO2 Electroreduction to Ethanol with Industrial Current Density

The efficient ethanol electrosynthesis from CO₂ is challenging with low selectivity at high CO₂ electrolysis rates, due to the competition with H₂ and other reduction products. Copper-based bimetallic electrocatalysts are potential candidates for the CO₂-to-ethanol conversion, but the secondary metal has mainly been focused on active components (such as Ag, Sn) for CO₂ electroreduction, which also promote selectivity of ethylene or other reduction products rather than ethanol. Limited attention has been given to alkali-earth metals due to their inherently active chemical property. Herein, we rationally synthesized a (111) facet-oriented nano Cu₂Mg (designated as Cu₂Mg(111)) intermetallic compound with high-density ordered Cu₃-Mg sites. The in situ Raman spectroscopy and density function theory calculations revealed that the Cu₃^{− −}-Mg^{− +} active sites allowed to increase *CO surface coverage, decrease reaction energy for *CO−CO coupling, and stabilize *CHCHOH intermediates, thus promoting the ethanol formation pathway. The Cu₂Mg(111) catalyst exhibited a high FE_C2H5OH of 76.2±4.8 % at 600 mA⋅cm⁻², and a peak value of |j_C2H5OH| of 720±34 mA⋅cm⁻², almost 4 times of that using conventional Cu₂Mg with (311) facets, comparable to the best reported values for the CO₂-to-ethanol electroreduction.     

Selective Carbonyl−C(sp3) Bond Cleavage To Construct Ynamides,Ynoates, and Ynones by Photoredox Catalysis

Carbon–carbon bond cleavage/functionalization is synthetically valuable, and selective carbonyl−C(sp³) bond cleavage/alkynylation presents a new perspective in constructing ynamides, ynoates, and ynones. Reported here is the first alkoxyl‐radical‐enabled carbonyl−C(sp³) bond cleavage/alkynylation reaction by photoredox catalysis. The use of novel cyclic iodine(III) reagents are essential for β‐carbonyl alkoxyl radical generation from β‐carbonyl alcohols, including alcohols with high redox potential ( >2.2 V vs. SCE in MeCN). β‐Amide, β‐ester, and β‐ketone alcohols yield ynamides, ynoates, and ynones, respectively, for the first time, with excellent regio‐ and chemoselectivity under mild reaction conditions.     

Anion‐aided Dynamic One‐pot Self‐assembly of Rectangular Metallacycles

The tetracopper(I) complex [{Cu₂(μ‐dppm)₂}₂(μ‐1,4‐O₂CC₆H₄ (CO₂ )₂)](BF₄ )₂ ( 1 (BF₄ )₂) and 1,2‐bis(4‐pyridyl)ethane (bpa) can establish a dynamic equilibrium in CH₂Cl₂ . From the equilibrium mixture containing 1 (BF₄ )₂ and bpa with the molar ratio 1 (BF₄ )₂/bpa of 1:1, a supramolecular compound [{Cu₂(μ‐dppm)₂}₂(μ‐1,4‐C₆H₄ (CO₂ )₂)(μ‐bpa)]₂(BF₄ )₄ ( 2 (BF₄ )₄) was obtained as single crystals. The crystal structure was determined by X‐ray crystallography to reveal presence of one anion inside a cationic rectangular metallacycle { 2 ⊂ BF₄ }³⁺. Both structural evidence and DFT ‐calculated results indicate that the F atoms of the anion exert weak electrostatic attraction with hydrogen atoms of the bound bpa as the framework of the cationic metallacycle. The attractive interactions apparently play an important role in stabilizing some dynamically self‐assembled precursors so as to form the final anion‐included metallacycle. Without the electrostatic help from the anion, the self‐assembly of the empty metallacycle may be hindered by a rather large endothermic free energy. The favorable electrostatic stabilization is present not only for a anion but also for other anions such as , , and even when the flexible bpa is replaced by rigid 4,4′‐bipyridine (bpy). Based on the DFT results, the metallacycle 2 (BF₄ )₄ can be easily prepared in a one‐pot reaction of [Cu(MeCN )₄](BF₄ ) with three ligands.     

Engineering the Coordination Environment of Single‐Atom Platinum Anchored on Graphdiyne for Optimizing Electrocatalytic Hydrogen Evolution

Two Pt single‐atom catalysts (SACs) of Pt‐GDY1 and Pt‐GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDY through the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five‐coordinated C₁‐Pt‐Cl₄ species in Pt‐GDY1 and four‐coordinated C₂‐Pt‐Cl₂ species in Pt‐GDY2. Pt‐GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with a mass activity up to 3.3 and 26.9 times more active than Pt‐GDY1 and the state‐of‐the‐art commercial Pt/C catalysts, respectively. Pt‐GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbs free energy of the hydrogen adsorption (|Δ |) at the Pt active sites, which are responsible for its excellent catalytic performance. This work can help better understand the structure–catalytic activity relationship in Pt SACs.     

Nanoscale MnII‐Coordination Polymers for Cell Imaging and Heterogeneous Catalysis

A mixed ligand approach was exploited to synthesize a new series of Mn^II‐based coordination polymers (CPs), namely, CP1 {[Mn(μ‐dpa)(μ‐4,4′‐bp)]?MeOH}_∞, CP2 {[Mn₃(μ‐dpa)₃(2,2′‐bp)₂]}_∞, CP3 {[Mn₃(μ‐dpa)₃(1,10‐phen)₂]?2 H₂O}_∞, CP4 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]?H₂O}_∞, CP5 {[Mn₂(μ‐dpa)₂(μ‐4,4′‐bpe)₂]? DEF}_∞, and CP6 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]? DMA}_∞ (dpa=3,5‐dicarboxyphenyl azide, 2,2′‐bp=2,2′‐bipyridine, 1,10‐phen=1,10‐phenanthroline, 4,4′‐bpe=1,2‐bis(4‐pyridyl)ethylene, 4,4′‐bp=4,4′‐bipyridine, DEF=N,N‐diethylformamide, DMA=N,N‐dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single‐crystal X‐ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four‐connected sql topology, whereas CP4 and CP6 exhibited a two‐dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.     

The Trifluoromethyl Anion: Evidence for [K(crypt‐222)]+

[K(crypt‐222)]⁺ ( 1 ) and [K(crypt‐222)]⁺ ( 3 ) are isostructural, displaying nearly identical unit cell parameters. The two structures are similar to the extent that the previously reported [K(crypt‐222)]⁺ model can be refined against the new data for [K(crypt‐222)]⁺ , with extra electron density being observed from the fourth fluorine atom of the . In agreement with experimental observations, theoretical calculations suggest that deprotonated [K(crypt‐222)]⁺ is highly unstable even at as low as 195 K. The previously considered 1:1 CHF ₃ clathrate of deprotonated [K(crypt‐222)]⁺ (crystallographically indistinguishable from 1 ) is ruled out on the basis of all available data.     

Tunable Self‐Assembly of Diblock Copolymers into Colloidal Particles with Triply Periodic Minimal Surfaces

We herein report the tunable self‐assembly of simple block copolymers, namely polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymers, into porous cubosomes with inverse or mesophases of controlled unit cell parameters as well as hexasomes with an inverse hexagonal (p 6mm ) structure, which have been rarely observed in polymer self‐assembly. A new morphological phase diagram was constructed for the solution self‐assembly of PS‐b‐PEO based on the volume fraction of the PS block against the initial copolymer concentration. The formation mechanisms of the cubosomes and hexasomes have also been revealed. This study not only affords a simple system for the controllable preparation and fundamental studies of ordered bicontinuous structures, but also opens up a new avenue towards porous architectures with highly ordered pores.     

Impact of Intramolecular Hydrogen Bonding on the Reactivity of Cupric Superoxide Complexes with O−H and C−H Substrates

The dioxygen reactivity of a series of TMPA‐based copper(I) complexes (TMPA=tris(2‐pyridylmethyl)amine), with and without secondary‐coordination‐sphere hydrogen‐bonding moieties, was studied at ?135 °C in 2‐methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H‐bonded [( TMPA)Cu^II(O₂^.?)]⁺ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)Cu^II(N₃^?)]⁺ azido analogues were compared, and the O₂^.? reactivity of ligand–Cu^I complexes when an H‐bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C?H bond‐dissociation energies is observed, correlating with the number and strength of the H‐bonding groups.     

Reentrant Structural Transitions and Collapse of Charge and Orbital Orders in Quadruple Perovskites

Charge and orbital degrees of freedom determine properties of many materials, and are central to many important phenomena. At high temperatures, thermal fluctuations overcome them, and high‐symmetry structures are realized. On decreasing temperature, different charge‐ and orbital‐order transitions take place accompanied by symmetry lowering. Remarkable exceptions to this general tendency, realized in Cu‐doped BiMn₇O₁₂ quadruple perovskites, are presented. Introduction of Cu²⁺ produces mixtures of Mn³⁺ and Mn⁴⁺ and charge degree of freedom. BiCuMn₆O₁₂ (and compositions in the vicinity) exhibits well‐defined 1:3 charge order of Mn⁴⁺ and Mn³⁺ and orbital order of Mn³⁺ near room temperature, but both charge and orbital orders collapse below about 115 K with the reentrance of the high‐temperature cubic Im phase. What is interesting the collapse can be controlled by a magnetic field even without long‐range magnetic order, and the collapsed phase shows nearly zero thermal expansion.