Observation of Transition-Metal–Boron Triple Bonds in IrB2O− and ReB2O−

Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal d_π→BR back-donation, despite the electron deficiency of boron. An electron-precise metal–boron triple bond was first observed in BiB₂O⁻ [Bi≡B−B≡O]⁻ in which both boron atoms can be viewed as sp-hybridized and the [B−BO]⁻ fragment is isoelectronic to a carbyne (CR). To search for the first electron-precise transition-metal-boron triple-bond species, we have produced IrB₂O⁻ and ReB₂O⁻ and investigated them by photoelectron spectroscopy and quantum-chemical calculations. The results allow to elucidate the structures and bonding in the two clusters. We find IrB₂O⁻ has a closed-shell bent structure (C_s, ¹A′) with BO⁻ coordinated to an Ir≡B unit, (⁻OB)Ir≡B, whereas ReB₂O⁻ is linear (C_∞v, ³Σ⁻) with an electron-precise Re≡B triple bond, [Re≡B−B≡O]⁻. The results suggest the intriguing possibility of synthesizing compounds with electron-precise M≡B triple bonds analogous to classical carbyne systems.     

Bismuth–Boron Multiple Bonding in BiB2O− and Bi2B−

Despite its electron deficiency, boron is versatile in forming multiple bonds. Transition‐metal–boron double bonding is known, but boron–metal triple bonds have been elusive. Two bismuth boron cluster anions, BiB₂O⁻ and Bi₂B⁻, containing triple and double B−Bi bonds are presented. The BiB₂O⁻ and Bi₂B⁻ clusters are produced by laser vaporization of a mixed B/Bi target and characterized by photoelectron spectroscopy and ab initio calculations. Well‐resolved photoelectron spectra are obtained and interpreted with the help of ab initio calculations, which show that both species are linear. Chemical bonding analyses reveal that Bi forms triple and double bonds with boron in BiB₂O⁻ ([Bi≡B−B≡O]⁻) and Bi₂B⁻ ([Bi=B=Bi]⁻), respectively. The Bi−B double and triple bond strengths are calculated to be 3.21 and 4.70 eV, respectively. This is the first experimental observation of Bi−B double and triple bonds, opening the door to design main‐group metal–boron complexes with multiple bonding.     

High‐Resolution Photoelectron Imaging of IrB3−: Observation of a π‐Aromatic B3+ Ring Coordinated to a Transition Metal

In a high‐resolution photoelectron imaging and theoretical study of the IrB₃^? cluster, two isomers were observed experimentally with electron affinities (EAs) of 1.3147(8) and 1.937(4) eV. Quantum calculations revealed two nearly degenerate isomers competing for the global minimum, both with a B₃ ring coordinated with the Ir atom. The isomer with the higher EA consists of a B₃ ring with a bridge‐bonded Ir atom (C_s , ²A′), and the second isomer features a tetrahedral structure (C_3v , ²A₁). The neutral tetrahedral structure was predicted to be considerably more stable than all other isomers. Chemical bonding analysis showed that the neutral C_3v isomer involves significant covalent Ir?B bonding and weak ionic bonding with charge transfer from B₃ to Ir, and can be viewed as an Ir–(η³‐B₃⁺) complex. This study provides the first example of a boron‐to‐metal charge‐transfer complex and evidence of a π‐aromatic B₃⁺ ring coordinated to a transition metal.     

Redox Non‐Innocent Behavior of a Terminal Iridium Hydrazido(2−) Triple Bond

The synthesis of the first terminal Group 9 hydrazido(2‐) complex, Cp*IrN(TMP) ( 6 ) (TMP=2,2,6,6‐tetramethylpiperidine) is reported. Electronic structure and X‐ray diffraction analysis indicate that this complex contains an Ir?N triple bond, similar to Bergman's seminal Cp*Ir(N^tBu) imido complex. However, in sharp contrast to Bergman's imido, 6 displays remarkable redox non‐innocent reactivity owing to the presence of the N_β lone pair. Treatment of 6 with MeI results in electron transfer from N_β to Ir prior to oxidative addition of MeI to the iridium center. This behavior opens the possibility of carrying out facile oxidative reactions at a formally Ir^III metal center through a hydrazido(2?)/isodiazene valence tautomerization.     

Dimetallapoly‐yn‐diylidynes: LnM≡C−(C≡C)x−C≡MLn (x=0–4)

Synthetic routes to dimetallated C_x carbon wires in which two metals are separated by a linear carbon chain involving terminal metal–carbon triple bonds are described for the complexes [(Tp*)(CO)₂W≡C?(C≡C)_n?C≡W(CO)₂(Tp*)] (Tp*=hydrotris(dimethylpyrazolyl)borate) where n=1, 3 or 4, joining the previously known examples with n=0, 1 and 2 to complete the series as models for linear carbyne C_∞.     

Synthese,Struktur und Eigenschaften der Komplexe [(Me2PhP)3Cl2Re≡N‐IrCl2(C5Me5)], [(Me2PhP)3Cl2Re≡N‐IrCl(COD)], [PPh4][O3Os≡N‐IrCl2(C5Me5)] und [PPh4][O3Os≡N‐IrCl(COD)] mit Nitridobrücken Re≡N‐Ir und Os≡N‐Ir

Synthesis and Crystal Structures of the Complexes [(Me₂PhP)₃Cl₂Re≡N‐IrCl₂(C₅Me₅)], [(Me₂PhP)₃Cl₂Re≡N‐IrCl(COD)], [PPh₄][O₃Os≡N‐IrCl₂(C₅Me₅)], and [PPh₄][O₃Os≡N‐IrCl(COD)] with Nitrido bridges Re≡N‐Ir and Os≡N‐Ir The heteronuclear complexes [(Me₂PhP)₃Cl₂Re≡N‐IrCl₂(C₅Me₅)] ( 1 ), [(Me₂PhP)₃Cl₂Re≡N‐IrCl(COD)] ( 2 ), [PPh₄][O₃Os≡N‐IrCl₂(C₅Me₅)] ( 3 ) and [PPh₄][O₃Os≡N‐IrCl(COD)] ( 4 ) were obtained by the reaction of the nitrido complexes [ReNCl₂(PMe₂Ph)₃] and [OsO₃N]^— with the iridium compounds [IrCl₂(C₅Me₅)]₂ and [IrCl(COD)]₂ in benzonitrile. 1 forms red crystals with the composition 1 ·C₆H₅CN in the monoclinic space group P2₁/c and a = 1264.7(2); b = 1945.3(2); c = 1835.4(1) pm, β = 90.35(1)°, Z = 4. The complex fragment [IrCl₂(C₅Me₅)] in the dinuclear complex is connected by an asymmetric nitrido bridge Re≡N‐Ir to the nitrido complex [ReNCl₂(PMe₂Ph)₃]. The nitrido bridge is characterized by a Re‐N‐Ir bond angle of 179.4(2)° and distances Re‐N = 170.9(4) pm and Ir‐N = 203.3(4) pm. 2 forms brownish red, triclinic crystals with the space group P1¯ and a = 1076.6(2), b = 1373.2(2), c = 1452.4(1) pm, α = 107.513(8), β = 101.843(9), γ = 110.04(1)°, Z = 2. The nitrido bridge to the complex fragment [IrCl(COD)] has a Re‐N‐Ir bond angle of 173, 8(4)° and distances Re‐N = 170, 4(8) pm and Ir‐N = 196, 2(8) pm. 3 crystallizes as monoclinic red crystals in the space group P2₁/n and a = 1449.9(2), b = 906.74(4), c = 2628.9(5) pm, β = 103.50(1)°, Z = 4. The nitrido bridge Os≡N‐Ir is slightly bent (Os‐N‐Ir = 165.0(3)°). The distances are Os‐N = 168.3(5) pm and Ir‐N = 201.9(5) pm. 4 forms dark brown, orthorhombic crystals with the space group P2₁2₁2₁ and a = 704.35(2), b = 1228.17(6), c = 3442.0(4) pm, Z = 4. The distances in the slightly bent nitrido bridge (Os‐N‐Ir = 161.8(4)°) are Os‐N = 169.3(7) pm und Ir‐N = 197.8(7) pm.     

Synthesis and Characterization of Dirhenadehydro[12]annulenes

The 12‐membered‐ring metallacycles [mer‐Re{≡CCH=C(R)C≡C?}Cl(PMe₂Ph)₃)]₂ (R=CMe₃, 1‐adamantyl), which are organometallic analogues of antiaromatic octadehydro[12]annulene, are prepared by heating the methyl carbyne complexes mer‐Re{≡CCH=C(R)C≡CH}(CH₃)Cl(PMe₂Ph)₃. An intermolecular σ‐bond metathesis between the Re?CH₃ bond and the acetylenic C?H bond is proposed for their formation.     

CO Oxidation Promoted by the Gold Dimer in Au2VO3− and Au2VO4− Clusters

Investigations on the reactivity of atomic clusters have led to the identification of the elementary steps involved in catalytic CO oxidation, a prototypical reaction in heterogeneous catalysis. The atomic oxygen species O^.? and O^2? bonded to early‐transition‐metal oxide clusters have been shown to oxidize CO. This study reports that when an Au₂ dimer is incorporated within the cluster, the molecular oxygen species O₂^2? bonded to vanadium can be activated to oxidize CO under thermal collision conditions. The gold dimer was doped into Au₂VO₄^? cluster ions which then reacted with CO in an ion‐trap reactor to produce Au₂VO₃^? and then Au₂VO₂^?. The dynamic nature of gold in terms of electron storage and release promotes CO oxidation and O? O bond reduction. The oxidation of CO by atomic clusters in this study parallels similar behavior reported for the oxidation of CO by supported gold catalysts.     

Synthese,Struktur und Eigenschaften der Komplexe [(H2O)Cl4Os≡N‐IrCl(C5Me5)(AsPh3)], [(Ph3Sb)Cl4Os≡N‐IrCl(C5Me5)(SbPh3)], [(Ph3Sb)2Cl3Os≡N‐IrCl(COD)] und [{(Me2PhP)2(CO)Cl2Re≡N}2ReNCl2(PMe2Ph)]

Synthesis, Crystal Structure, and Properties of the Complexes [(H₂O)Cl₄Os≡N‐IrCl(C₅Me₅)(AsPh₃)], [(Ph₃Sb)Cl₄Os≡N‐IrCl(C₅Me₅)(SbPh₃)], [(Ph₃Sb)₂Cl₃Os≡N‐IrCl(COD)] and [{(Me₂PhP)₂(CO)Cl₂Re≡N}₂ReNCl₂(PMe₂Ph)] The dinuclear complexes [(H₂O)Cl₄Os≡N‐IrCl(C₅Me₅)(AsPh₃)]·H₂O ( 1 ·H₂O), [(Ph₃Sb)Cl₄Os≡N‐IrCl(C₅Me₅)(SbPh₃)] ( 2 ), and [(Ph₃Sb)₂Cl₃Os≡N‐IrCl(COD)] ( 3 ) result from the reaction of the nitrido complexes [(Ph₃As)₂OsNCl₃] and [(Ph₃Sb)₂OsNCl₃] with the iridium compounds [IrCl₂(C₅Me₅)]₂ and [IrCl(COD)]₂ in dichloromethane. 1 crystallizes as 1 ·H₂O in form of green platelets in the monoclinic space group Cm and a = 1105.53(6); b = 1486.76(9); c = 2024.88(10) pm, β = 97.191(4)°, Z = 4. The formation of 1 in air involves a ligand exchange, and the coordination of a water molecule in trans position to the Os‐N triple bond. The resulting complex fragments [(H₂O)Cl₄Os≡N] and [IrCl(C₅Me₅)(AsPh₃)] are connected by an asymmetric nitrido bridge Os≡N‐Ir. The nitrido bridge is characterised by an Os‐N‐Ir bond angle of 173.7(7)°, and distances Os‐N = 168(1) pm and Ir‐N = 191(1) pm. 2 crystallizes in clumped together brown platelets with the space group and a = 1023.3(3), b = 1476.2(3), c = 1872.5(6) pm, α = 74.60(2), β = 73.84(2), γ = 76.19(2)°, Z = 2. In 2 the asymmetric nitrido bridge Os≡N‐Ir joins the two complex fragments [(Ph₃Sb)Cl₄Os≡N] and [IrCl(C₅Me₅)(SbPh₃)], which are formed by a ligand exchange reaction. 3 forms dark green crystals with the triclinic space group and a = 1079.4(1), b = 1172.3(1), c = 1696.7(2) pm, α = 101.192(9),β = 92.70(1), γ = 92.61(1)°, Z = 2. The distances in the almost linear nitrido bridge (Os≡N‐Ir = 175.3(7)°) are Os‐N = 171(1) pm and Ir‐N = 183(1) pm. The reaction of [ReNCl₂(PMe₂Ph)₃] with [Mo(CO)₃(NCMe)₃] unexpectedly affords the trinuclear complex [{(Me₂PhP)₂(OC)Cl₂Re≡N}₂ReNCl₂(PMe₂Ph)] ( 4 ) as the main product. It forms triclinic brown crystals with the composition 4 ·2THF and the space group (a = 1382.70(7), b = 1498.58(7), c = 1760.4(1) pm, α = 99.780(7), β = 99.920(7), γ = 114.064(6)°, Z = 2). In the trinuclear complex, the central fragment, [ReNCl₂(PMe₂Ph)] is joined in trans position to two nitrido complexes [(Me₂PhP)₂(CO)Cl₂Re≡N], giving an almost linear Re≡N‐Re‐N≡Re arrangement. The bond angles and distances in the nitrido bridges are Re‐N‐Re = 167.8(3)°, Re‐N = 171.1(8) pm and 204.2(8) pm; and Re‐N‐Re = 168.1(4)°, Re‐N = 170.9(9) and 203.5(9) pm respectively. As expected, the Re‐N bond length to the terminal nitrido ligand on the central Re atom is much shorter at 161.2(9) pm than the triple bonds of the asymmetric bridges.     

B−B Bond Nucleophilicity in a Tetraaryl μ‐Hydridodiborane(4) Anion

The tetraaryl μ‐hydridodiborane(4) anion [ 2 H]^? possesses nucleophilic B?B and B?H bonds. Treatment of K[ 2 H] with the electrophilic 9‐H‐9‐borafluorene (HBFlu) furnishes the B₃ cluster K[ 3 ], with a triangular boron core linked through two BHB two‐electron, three‐center bonds and one electron‐precise B?B bond, reminiscent of the prominent [B₃H₈]^? anion. Upon heating or prolonged stirring at room temperature, K[ 3 ] rearranges to a slightly more stable isomer K[ 3 a ]. The reaction of M[ 2 H] (M⁺=Li⁺, K⁺) with MeI or Me₃SiCl leads to equimolar amounts of 9‐R‐9‐borafluorene and HBFlu (R=Me or Me₃Si). Thus, [ 2 H]^? behaves as a masked [:BFlu]^? nucleophile. The HBFlu by‐product was used in situ to establish a tandem substitution‐hydroboration reaction: a 1:1 mixture of M[ 2 H] and allyl bromide gave the 1,3‐propylene‐linked ditopic 9‐borafluorene 5 as sole product. M[ 2 H] also participates in unprecedented [4+1] cycloadditions with dienes to furnish dialkyl diaryl spiroborates, M[R₂BFlu].     

Ligand‐Centred Reactivity of Bis(picolyl)amine Iridium: Sequential Deprotonation,Oxidation and Oxygenation of a “Non‐Innocent” Ligand

Treatment of [Ir(bpa)(cod)]⁺ complex [ 1 ]⁺ with a strong base (e.g., tBuO^?) led to unexpected double deprotonation to form the anionic [Ir(bpa?2H)(cod)]^? species [ 3 ]^?, via the mono‐deprotonated neutral amido complex [Ir(bpa?H)(cod)] as an isolable intermediate. A certain degree of aromaticity of the obtained metal–chelate ring may explain the favourable double deprotonation. The rhodium analogue [ 4 ]^? was prepared in situ. The new species [M(bpa?2H)(cod)]^? (M=Rh, Ir) are best described as two‐electron reduced analogues of the cationic imine complexes [M^I(cod)(Py‐CH₂‐N?CH‐Py)]⁺. One‐electron oxidation of [ 3 ]^? and [ 4 ]^? produced the ligand radical complexes [ 3 ]^. and [ 4 ]^.. Oxygenation of [ 3 ]^? with O₂ gave the neutral carboxamido complex [Ir(cod)(py‐CH₂‐N‐CO‐py)] via the ligand radical complex [ 3 ]^. as a detectable intermediate.     

Boron-Made N2: Realization of a B≡B Triple Bond in the B2Al3− Cluster

Until now, all B≡B triple bonds have been achieved by adopting two ligands in the L→B≡B←L manner. Herein, we report an alternative route of designing the B≡B bonds based on the assumption that by acquiring two extra electrons, an element with the atomic number Z can have properties similar to those of the element with the atomic number Z+2. Specifically, we show that due to the electron donation from Al to B, the negatively charged B≡B kernel in the B₂Al₃⁻ cluster mimics a triple N≡N bond. Comprehensive computational searches reveal that the global minimum structure of B₂Al₃⁻ exhibits a direct B–B distance of 1.553 Å, and its calculated electron vertical detachment energies are in excellent agreement with the corresponding values of the experimental photoelectron spectrum. Chemical bonding analysis revealed one σ and two π bonds between the two B atoms, thus confirming a classical textbook B≡B triple bond, similar to that of N₂.     

The lifetimes of gas phase CO2˙− and N2O˙− calculated from the transition probability of the autodetachment process A− → A + e−

A procedure to calculate the quantum mechanical transition probability of a unimolecular primary chemical process, A^? → A + e^? is investigated for the circumstance where A^? and A have different numbers of vibrational and rotational degrees of freedom (one is linear, the other not). A procedure is introduced to deal with the coupling between the vibrational and rotational motions. The proposed method was applied to calculating the lifetimes of CO₂^˙? and N₂O^˙? in the gas phase. The geometry optimizations and frequency calculations for CO₂, CO₂^˙?, N₂O, and N₂O^˙? are performed at HF, MP2, and QCISD(T) levels with 6-31G* or 6–31+G* basis sets, in order to obtain reliable geometric and spectroscopic information on these systems. Lifetimes are calculated for several of the lower vibrational–rotational states of the anions, as well as for the Boltzmann distribution of states at 298 K. The lifetime of the lowest vibrational–rotational state of CO₂^˙?, is 1.03 × 10^?4 s, and of the lowest vibrational state with rotational levels weighted by Boltzmann distribution at 298 K, 1.50 × 10^?4 s. These values are in good agreement with the experimental number, 9.0 ± 2.0 × 10^?5 s, and support the experimental evidence that CO₂^˙? was formed in its ground vibrational level by the techniques used. The lifetime of CO₂^˙? calculated with Boltzmann distribution over its vibrational and rotational levels at 298 K, is 1.51 × 10^?5 s. There are no direct measurements of the lifetime of N₂O^˙?, but it was estimated to be greater than 10^?4 s from experimental evidence. The predicted lifetimes of N₂O^˙?, at its lowest vibrational–rotational state (0 K) and lowest vibrational state with rotational levels weighted by the Boltzmann distribution at 298 K, are 238 and 19.1 s, respectively. The lifetime of N₂O^˙? at thermal equilibrium at 298 K is 6.66 × 10^?2 s, indicating that electron loss from the excited vibrational states of N₂O^˙? is significant. This study represents the first theoretical investigation of CO₂^˙? and N₂O^˙? lifetimes. © 1994 John Wiley & Sons, Inc.     

Metal‐Free Oxidative B−N Coupling of nido‐Carborane with N‐Heterocycles

A general method for the oxidative substitution of nido‐carborane (7,8‐C₂B₉H₁₂^?) with N‐heterocycles has been developed by using 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) as an oxidant. This metal‐free B?N coupling strategy, in both inter‐ and intramolecular fashions, gave rise to a wide array of charge‐compensated, boron‐substituted nido‐carboranes in high yields (up to 97 %) with excellent functional‐group tolerance under mild reaction conditions. The reaction mechanism was investigated by density‐functional theory (DFT) calculations. A successive single‐electron transfer (SET), B?H hydrogen‐atom transfer (HAT), and nucleophilic attack pathway is proposed. This method provides a new approach to nitrogen‐containing carboranes with potential applications in medicine and materials.     

Analysis of Why Boron Avoids sp2 Hybridization and Classical Structures in the BnHn+2 Series

We performed global minimum searches for the B_nH_n+2 (n=2‐5) series and found that classical structures composed of 2c–2e B? H and B? B bonds become progressively less stable along the series. Relative energies increase from 2.9 kcal mol^?1 in B₂H₄ to 62.3 kcal mol^?1 in B₅H₇. We believe this occurs because boron atoms in the studied molecules are trying to avoid sp² hybridization and trigonal structure at the boron atoms, as in that case one 2p‐AO is empty, which is highly unfavorable. This affinity of boron to have some electron density on all 2p‐AOs and avoiding having one 2p‐AO empty is a main reason why classical structures are not the most stable configurations and why multicenter bonding is so important for the studied boron–hydride clusters as well as for pure boron clusters and boron compounds in general.     

Alkylidinphosphane und -arsane. I [P ≡ C?S]−[Li(dme)3]+ – Synthese und Struktur

Alkylidynephosphanes and -arsanes. I [P ≡ C? S]^?[Li(dme)₃]⁺ – Synthesis and Structure O,O′-Diethyl thiocarbonate and bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide dissolved in 1,2-dimethoxyethane, react below 0°C to give ethoxy trimethylsilane and tris(1,2-dimethoxyethane-O,O′)lithium 2λ³-phosphaethynylsulfanide – [P≡C? S]^? [Li(dme)₃]⁺ – ( 1a ). Apart from bis(trimethylsilyl)sulfane or carbon oxide sulfide, dark red concentrated solutions of λ³-phosphaalkyne 1 are also obtained from reactions of carbon disulfide with bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide or with the homologous lithoxy-methylidynephosphane ( 2 ) [1]. The ir spectrum shows two absorptions at 1762 and 747 cm^?1 characteristic for the P≡C and C? S stretching vibrations. The nmr parameters {δ(³¹P) ? 121.3; δ(¹³C) 190.8 ppm; ¹J_CP 18.2 Hz} resemble much more values of diorganylamino-2λ³-phosphaalkynes than those of bis(1,2-dimethoxyethane-O,O′)lithoxy-methylidyne-phosphane ( 2a ). As found by an X-ray structure analysis (P2₁/c; a = 1192.6(16); b = 1239.1(19); c = 1414.8(26) pm; β = 105.91(13)° at ?100 ± 3°C; Z = 4 formula units; wR = 0.064) of pale yellow crystals (mp. + 16°C) isolated from the reaction with O,O′-diethyl thiocarbonate, the solid is built up of separate [P≡C? S]^? and [Li(dme)₃]⁺ ions. Typical bond lengths and angles are: P≡C 155.5(11); C? S 162.0(11); Li? O 206.4(17) to 220.3(20) pm; P≡C? S 178.9(7)°.     

Valence‐to‐Core X‐ray Emission Spectroscopy as a Probe of O−O Bond Activation in Cu2O2 Complexes

Valence‐to‐Core (VtC) X‐ray emission spectroscopy (XES) was used to directly detect the presence of an O?O bond in a complex comprising the [Cu^II₂(μ‐η²:η²‐O₂)]²⁺ core relative to its isomer with a cleaved O?O bond having a [Cu^III₂(μ‐O)₂]²⁺ unit. The experimental studies are complemented by DFT calculations, which show that the unique VtC XES feature of the [Cu^II₂(μ‐η²:η²‐O₂)]²⁺ core corresponds to the copper stabilized in‐plane 2p π peroxo molecular orbital. These calculations illustrate the sensitivity of VtC XES for probing the extent of O?O bond activation in μ‐η²:η²‐O₂ species and highlight the potential of this method for time‐resolved studies of reaction mechanisms.     

Strong N−X⋅⋅⋅O−N Halogen Bonds: A Comprehensive Study on N‐Halosaccharin Pyridine N‐Oxide Complexes

A study of the strong N?X???^?O?N⁺ (X=I, Br) halogen bonding interactions reports 2×27 donor×acceptor complexes of N‐halosaccharins and pyridine N‐oxides (PyNO). DFT calculations were used to investigate the X???O halogen bond (XB) interaction energies in 54 complexes. A simplified computationally fast electrostatic model was developed for predicting the X???O XBs. The XB interaction energies vary from ?47.5 to ?120.3 kJ mol^?1; the strongest N?I???^?O?N⁺ XBs approaching those of 3‐center‐4‐electron [N?I?N]⁺ halogen‐bonded systems (ca. 160 kJ mol^?1). ¹H NMR association constants (K_XB) determined in CDCl₃ and [D₆]acetone vary from 2.0×10⁰ to >10⁸ m ^?1 and correlate well with the calculated donor×acceptor complexation enthalpies found between ?38.4 and ?77.5 kJ mol^?1. In X‐ray crystal structures, the N‐iodosaccharin‐PyNO complexes manifest short interaction ratios (R_XB) between 0.65–0.67 for the N?I???^?O?N⁺ halogen bond.     

Catalytic CO Oxidation by O2 Mediated by Noble‐Metal‐Free Cluster Anions Cu2VO3–5−

Catalytic CO oxidation by molecular O₂ is an important model reaction in both the condensed phase and gas‐phase studies. Available gas‐phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O₂ under thermal collision conditions. Herein, we identified the first example of noble‐metal‐free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu₂VO_3–5^? for CO oxidation by O₂. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu?Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O₂ activation during the catalysis.     

Pothole‐rich Ultrathin WO3 Nanosheets that Trigger N≡N Bond Activation of Nitrogen for Direct Nitrate Photosynthesis

Nitrate is a raw ingredient for the production of fertilizer, gunpowder, and explosives. Developing an alternative approach to activate the N≡N bond of naturally abundant nitrogen to form nitrate under ambient conditions will be of importance. Herein, pothole‐rich WO₃ was used to catalyse the activation of N≡N covalent triple bonds for the direct nitrate synthesis at room temperature. The pothole‐rich structure endues the WO₃ nanosheet more dangling bonds and more easily excited high momentum electrons, which overcome the two major bottlenecks in N≡N bond activation, that is, poor binding of N₂ to catalytic materials and the high energy involved in this reaction. The average rate of nitrate production is as high as 1.92 mg g^?1 h^?1 under ambient conditions, without any sacrificial agent or precious‐metal co‐catalysts. More generally, the concepts will initiate a new pathway for triggering inert catalytic reactions.