ThC2@C82versus Th@C84: unexpected formation of triangular thorium carbide cluster inside fullerenes

Synthesis of the first thorium-containing clusterfullerenes, ThC₂@C_s(6)–C₈₂ and ThC₂@C₂(5)–C₈₂, is reported. These two novel actinide fullerene compounds were characterized by mass spectrometry, single-crystal X-ray diffraction crystallography, UV–vis–NIR spectroscopy, and theoretical calculations. Crystallographic studies reveal that the encapsulated ThC₂ clusters in both C_s(6)–C₈₂ and C₂(5)–C₈₂ feature a novel bonding structure with one thorium metal center connected by a C C unit, forming an isosceles triangular configuration, which has not been hitherto observed for endohedral fullerenes or for solid phase thorium carbides. Electronic structure calculations assign a formal electronic structure of [Th⁴⁺(C₂)²⁻]²⁺@[C₈₂]²⁻, with pronounced donation bonding from (C₂)²⁻ to Th⁴⁺, secondary backbonding from the fullerene to thorium and Th–C double bond character in both compounds. This work presents a new family of endohedral fullerenes, MC₂@C_2n−2, being unexpected isomers of MC_2n, and provides broader understanding of thorium bonding.

The first thorium-containing cluster fullerenes, ThC₂@C_s(6)–C₈₂ and ThC₂@C₂(5)–C₈₂, were synthesized and characterized. ThC₂ clusters in both C₈₂ cages feature a novel bonding structure with thorium metal and C C forming an isosceles triangular configuration.     

Visible light-induced oxidative N-dealkylation of alkylamines by a luminescent osmium(vi) nitrido complex

N-Dealkylation of amines by metal oxo intermediates (M O) is related to drug detoxification and DNA repair in biological systems. In this study, we report the first example of N-dealkylation of various alkylamines by a luminescent osmium(vi) nitrido complex induced by visible light.

The visible light-induced N-dealkylation of various alkylamines by a luminescent osmium(vi) nitrido complex has been investigated. We provide definitive evidence that these reactions occur via an ET/PT mechanism.

High-valent metal oxo (M O) species play key roles in many chemical and biological oxidation processes.¹ They are versatile oxidants that can perform oxidation of substrates via a variety of pathways, including electron transfer, H-atom transfer, hydride transfer and O-atom transfer. In principle, high-valent metal nitrido (M N) complexes should also function as versatile oxidants similar to M O. Although there have been significant advances in M N oxidation chemistry in recent years, the reactivity of M N is still rather limited in scope compared to M O.² M N is intrinsically less oxidizing than M O due to the stronger electron donating property of the N³⁻ ligand than the O²⁻ ligand. Attempts to increase the oxidizing power of M N by increasing the oxidation state or by using less electron-donating ancillary ligands often led to decomposition of the complexes, mainly due to facile coupling of the nitrido ligands to yield N₂ (2M N → 2M + N₂).³ One appealing strategy to enhance the reactivity of M N is photochemical excitation. We have recently designed an osmium(vi) nitrido complex [Os^VI(N)(L)(CN)₃]⁻ (NO2-OsN, HL = 2-(2-hydroxy-5-nitrophenyl)benzoxazole) that is strongly luminescent in the solid state and in fluid solutions.⁴ It readily absorbs visible light to generate a long-lived and highly oxidizing excited state with a redox potential of ca. 1.4 V. The excited state of this complex also possesses [Os N˙] nitridyl characteristics that enable it to readily abstract H-atoms from inert organic substrates.⁵We report herein the visible-light induced N-dealkylation of various alkylamines by NO2-OsN. Iron oxo species have been used by heme and nonheme enzymes to carry out N-dealkylation reactions of tertiary amines, which are important processes involved in detoxification and DNA repair.⁶ A number of synthetic iron(iv) oxo complexes are also able to carry out such N-dealkylation reactions.⁷ Mechanistic studies using cytochrome P₄₅₀ and synthetic iron oxo complexes indicate that there are two possible mechanisms for N-dealkylation of amines, namely hydrogen-atom transfer (HAT) and electron transfer–proton transfer (ET–PT) (Fig. 1).⁸ In this work we report the first example of N-dealkylation of various aromatic as well as aliphatic tertiary amines by a nitrido complex upon visible light excitation. We also provide unambiguous evidence that these reactions occur via an ET/PT mechanism.Open in a separate windowFig. 1Two possible mechanisms for N-demethylation of tertiary amines by cytochrome P₄₅₀ and synthetic Fe(iv) oxo complexes (P = porphyrin).     

Unraveling the reactivity of a cationic iminoborane: avenues to unusual boron cations

A cationic terminal iminoborane [Mes*N B ← IPr₂Me₂][AlBr₄] (3⁺[AlBr₄]⁻) (Mes* = 2,4,6-tri-tert-butylphenyl and IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) has been synthesized and characterized. The employment of an aryl group and N-heterocyclic carbene (NHC) ligand enables 3⁺[AlBr₄]⁻ to exhibit both B-centered Lewis acidity and BN multiple bond reactivities, thus allowing for the construction of tri-coordinate boron cations 5⁺–12⁺. More importantly, initial reactions involving coordination, addition, and [2 + 3] cycloadditions have been observed for the cationic iminoborane, demonstrating the potential to build numerous organoboron species via several synthetic routes.

An NHC-stabilized aryliminoboryl cation exhibits both boron-centered Lewis acidity and multiple bond reactivity and could be utilized as an effective synthon for unusual cationic boron species.     

Isolable acetylene complexes of copper and silver

Copper and silver play important roles in acetylene transformations but isolable molecules with acetylene bonded to Cu(i) and Ag(i) ions are scarce. This report describes the stabilization of π-acetylene complexes of such metal ions supported by fluorinated and non-fluorinated, pyrazole-based chelators. These Cu(i) and Ag(i) complexes were formed readily in solutions under an atmosphere of excess acetylene and the appropriate ligand supported metal precursor, and could be isolated as crystalline solids, enabling complete characterization using multiple tools including X-ray crystallography. Molecules that display κ²-or κ³-ligand coordination modes and trigonal planar or tetrahedral metal centers have been observed. Different trends in coordination shifts of the acetylenic carbon resonance were revealed by ¹³C NMR spectroscopy for the Cu(i) and Ag(i) complexes. The reduction in acetylene _{C C} due to metal ion coordination is relatively large for copper adducts. Computational tools were also used to quantitatively understand in detail the bonding situation in these species. It is found that the interaction between the transition metal fragment and the acetylene ligand is significantly stronger in the copper complexes, which is consistent with the experimental findings. The C C distance of these copper and silver acetylene complexes resulting from routine X-ray models suffers due to incomplete deconvolution of thermal smearing and anisotropy of the electron density in acetylene, and is shorter than expected. A method to estimate the C C distance of these metal complexes based on their experimental _{C C} is also presented.

Gaseous acetylene can be trapped on copper(i) and silver(i) sites supported by pyrazole-based scorpionates to produce isolable molecules for detailed investigations and the study of metal-acetylene bonding.     

Metalation-induced denitrogenative reductive coupling of isocyanides on a silylene-bridged nickel cluster

The denitrogenative reductive coupling of two molecules of CN^tBu to afford a disilylketenimine with an aza-disilacyclobutane skeleton was achieved on a multinuclear silylene-bridged Ni cluster framework in the absence of any strong reducing reagents. During this reaction, sequential cleavage of a C N bond and formation of a C C bond involving two molecules of CN^tBu were achieved on a nickel cluster surrounded by four silylene moieties. First, the cleavage of the C N bond of one molecule of CN^tBu provided a silylene-supported carbide and an N^tBu moiety on the dinuclear nickel skeleton. Further metalation induced coupling between the carbide moiety and an additional molecule of CN^tBu on the pentanuclear nickel-cluster framework to form a moiety via formation of a C C bond. Thermolysis of this pentanuclear cluster produced a disilylketenimine with an aza-disilacyclobutane skeleton in 58% yield.

The denitrogenative reductive coupling of two molecules of CN^tBu was achieved on a multinuclear silylene-bridged Ni cluster framework, and two possible intermediary Ni clusters were isolated.     

In situ modification of the d-band in the core–shell structure for efficient hydrogen storage via electrocatalytic N2 fixation

The electrochemical N₂ reduction reaction (NRR) into NH₃, especially powered by clean and renewable electricity, is a promising alternative to the capital- and energy-intensive Haber–Bosch process. However, the inert N N bond and the frantic competition of the hydrogen evolution reaction lead to a poor NH₃ yield rate and faradaic efficiency (FE). Here, we in situ construct a series of two-dimension core/shell V₂O₃/VN nanomeshes with a gradient nitride-layer thickness. Among them, V₂O₃/VN-2 exhibits the highest FE of 34.9%, an excellent NH₃ yield rate of 59.7 μg h⁻¹ mg_cat.⁻¹, and outstanding cycle stability, exceeding those of most of the NRR electrocatalysts reported to date. First-principles calculations reveal that the d-band center of VN shifts up in a nearly linear manner with the decrease of nitride-layer thickness, and V₂O₃/VN-2 with a d-band center closer to the Fermi level can strengthen the d–2π* coupling between the catalyst and N₂ molecule, notably facilitating the N₂-into-NH₃ conversion.

In 2D core/shell V₂O₃/VN nanomeshes with a gradient nitride-layer thickness, the V₂O₃ core can tune the d-band structure of the VN shell, strengthen the interaction between N₂ and the active site, and thus enhance electrochemical NRR performance.     

IR linewidth and intensity amplifications of nitrile vibrations report nuclear-electronic couplings and associated structural heterogeneity in radical anions

Conjugated molecular chains have the potential to act as “molecular wires” that can be employed in a variety of technologies, including catalysis, molecular electronics, and quantum information technologies. Their successful application relies on a detailed understanding of the factors governing the electronic energy landscape and the dynamics of electrons in such molecules. We can gain insights into the energetics and dynamics of charges in conjugated molecules using time-resolved infrared (TRIR) detection combined with pulse radiolysis. Nitrile ν(C N) bands can act as IR probes for charges, based on IR frequency shifts, because of their exquisite sensitivity to the degree of electron delocalization and induced electric field. Here, we show that the IR intensity and linewidth can also provide unique and complementary information on the nature of charges. Quantifications of IR intensity and linewidth in a series of nitrile-functionalized oligophenylenes reveal that the C N vibration is coupled to the nuclear and electronic structural changes, which become more prominent when an excess charge is present. We synthesized a new series of ladder-type oligophenylenes that possess planar aromatic structures, as revealed by X-ray crystallography. Using these, we demonstrate that C N vibrations can report charge fluctuations associated with nuclear movements, namely those driven by motions of flexible dihedral angles. This happens only when a charge has room to fluctuate in space.

Quantification of the intensity and linewidth of the ν(C N) IR band in a series of neutral and anionic nitrile-functionalized oligophenylenes reveals that the C N vibration is coupled to nuclear and electronic structural changes.     

Synthesis and electronic structure analysis of the actinide allenylidenes, [{(NR2)3}An(CCCPh2)]− (An = U,Th; R = SiMe3)

The reaction of [AnCl(NR₂)₃] (An = U, Th, R = SiMe₃) with in situ generated lithium-3,3-diphenylcyclopropene results in the formation of [{(NR₂)₃}An(CH C CPh₂)] (An = U, 1; Th, 2) in good yields after work-up. Deprotonation of 1 or 2 with LDA/2.2.2-cryptand results in formation of the anionic allenylidenes, [Li(2.2.2-cryptand)][{(NR₂)₃}An(CCCPh₂)] (An = U, 3; Th, 4). The calculated ¹³C NMR chemical shifts of the C_α, C_β, and C_γ nuclei in 2 and 4 nicely reproduce the experimentally assigned order, and exhibit a characteristic spin–orbit induced downfield shift at C_α due to involvement of the 5f orbitals in the Th–C bonds. Additionally, the bonding analyses for 3 and 4 show a delocalized multi-center character of the ligand π orbitals involving the actinide. While a single–triple–single-bond resonance structure (e.g., An–C C–CPh₂) predominates, the An C C CPh₂ resonance form contributes, as well, more so for 3 than for 4.

The actinide allenylidenes [{(NR₂)₃}An(CCCPh₂)]⁻ (An = U, Th, R = SiMe₃) feature significant ligand-to-metal donation bonding and partial An C double bond character.     

Nitrogen activation and cleavage by a multimetallic uranium complex

Multimetallic-multielectron cooperativity plays a key role in the metal-mediated cleavage of N₂ to nitrides (N³⁻). In particular, low-valent uranium complexes coupled with strong alkali metal reducing agents can lead to N₂ cleavage, but often, it is ambiguous how many electrons are transferred from the uranium centers to cleave N₂. Herein, we designed new dinuclear uranium nitride complexes presenting a combination of electronically diverse ancillary ligands to promote the multielectron transformation of N₂. Two heteroleptic diuranium nitride complexes, [K{U^IV(OSi(O^tBu)₃)(N(SiMe₃)₂)₂}₂(μ-N)] (1) and [Cs{U^IV(OSi(O^tBu)₃)₂(N(SiMe₃)₂)}₂(μ-N)] (3-Cs), containing different combinations of OSi(O^tBu)₃ and N(SiMe₃)₂ ancillary ligands, were synthesized. We found that both complexes could be reduced to their U(iii)/U(iv) analogues, and the complex, [K₂{U^IV/III(OSi(O^tBu)₃)₂(N(SiMe₃)₂)}₂(μ-N)] (6-K), could be further reduced to a putative U(iii)/U(iii) species that is capable of promoting the 4e⁻ reduction of N₂, yielding the N₂⁴⁻complex [K₃{U^V(OSi(O^tBu)₃)₂(N(SiMe₃)₂)}₂(μ-N)(μ-η²:η²-N₂)], 7. Parallel N₂ reduction pathways were also identified, leading to the isolation of N₂ cleavage products, [K₃{U^VI(OSi(O^tBu)₃)₂(N(SiMe₃)₂)( N)}(μ-N)₂{U^V(OSi(O^tBu)₃)₂(N(SiMe₃)₂)}]₂, 8, and [K₄{(OSi(O^tBu)₃)₂U^V)( N)}(μ-NH)(μ-κ²:C,N-CH₂SiMe₂NSiMe₃)-{U^V(OSi(O^tBu)₃)₂][K(N(SiMe₃)₂]₂, 9. These complexes provide the first example of N₂ cleavage to nitride by a uranium complex in the absence of reducing alkali metals.

Combinations of ligands were used to tune U N U complexes yielding a U(iii)/U(iii) nitride, which activates N₂. Parallel N₂ reduction pathways were identified, leading to the first example of N₂ cleavage by U without external alkali reducing agents.     

Syntheses,homeomorphic and configurational isomerizations,and structures of macrocyclic aliphatic dibridgehead diphosphines; molecules that turn themselves inside out

The diphosphine complexes cis- or trans- PtCl₂(P((CH₂)_n)₃P ) (n = b/12, c/14, d/16, e/18) are demetalated by MC X nucleophiles to give the title compounds (P((CH₂)_n)₃)P (3b–e, 91–71%). These “empty cages” react with PdCl₂ or PtCl₂ sources to afford trans- MCl₂(P((CH₂)_n)₃P ). Low temperature ³¹P NMR spectra of 3b and c show two rapidly equilibrating species (3b, 86 : 14; 3c, 97 : 3), assigned based upon computational data to in,in (major) and out,out isomers. These interconvert by homeomorphic isomerizations, akin to turning articles of clothing inside out (3b/c: ΔH^‡ 7.3/8.2 kcal mol⁻¹, ΔS^‡ −19.4/−11.8 eu, minor to major). At 150 °C, 3b, c, e epimerize to (60–51) : (40–49) mixtures of (in,in/out,out) : in,out isomers, which are separated via the bis(borane) adducts 3b, c, e·2BH₃. The configurational stabilities of in,out-3b, c, e preclude phosphorus inversion in the interconversion of in,in and out,out isomers. Low temperature ³¹P NMR spectra of in,out-3b, c reveal degenerate in,out/out,in homeomorphic isomerizations (ΔG^‡_Tc 12.1, 8.5 kcal mol⁻¹). When (in,in/out,out)-3b, c, e are crystallized, out,out isomers are obtained, despite the preference for in,in isomers in solution. The lattice structures are analyzed, and the D₃ symmetry of out,out-3c enables a particularly favorable packing motif. Similarly, (in,in/out,out)-3c, e·2BH₃ crystallize in out,out conformations, the former with a cycloalkane solvent guest inside.

It’s not a magic trick. Molecules can turn themselves inside out, just like articles of clothing or other familiar household objects. This behavior is demonstrated for the title compounds through a combination of synthesis, rate, and NMR studies.     

Copper(ii) ketimides in sp3 C–H amination

Commercially available benzophenone imine (HN CPh₂) reacts with β-diketiminato copper(ii) tert-butoxide complexes [Cu^II]–O^tBu to form isolable copper(ii) ketimides [Cu^II]–N CPh₂. Structural characterization of the three coordinate copper(ii) ketimide [Me₃NN]Cu–N CPh₂ reveals a short Cu-N_ketimide distance (1.700(2) Å) with a nearly linear Cu–N–C linkage (178.9(2)°). Copper(ii) ketimides [Cu^II]–N CPh₂ readily capture alkyl radicals R˙ (PhCH(˙)Me and Cy˙) to form the corresponding R–N CPh₂ products in a process that competes with N–N coupling of copper(ii) ketimides [Cu^II]–N CPh₂ to form the azine Ph₂C N–N CPh₂. Copper(ii) ketimides [Cu^II]–N CAr₂ serve as intermediates in catalytic sp³ C–H amination of substrates R–H with ketimines HN CAr₂ and ^tBuOO^tBu as oxidant to form N-alkyl ketimines R–N CAr₂. This protocol enables the use of unactivated sp³ C–H bonds to give R–N CAr₂ products easily converted to primary amines R–NH₂via simple acidic deprotection.

Commercially available benzophenone imine (HN CPh₂) reacts with β-diketiminato copper(ii) tert-butoxide complexes [Cu^II]–O^tBu to form isolable copper(ii) ketimides [Cu^II]–N CPh₂ that serve as intermediates in catalytic sp³ C−H amination via radical relay.     

Scaffold-based [Fe]-hydrogenase model: H2 activation initiates Fe(0)-hydride extrusion and non-biomimetic hydride transfer

We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor. In comparison to other non-scaffolded acyl-containing complexes, the complex described herein retains molecularly well-defined chemistry upon addition of multiple equivalents of exogenous base. Clean deprotonation of the acyl(methylene) C–H bond with a phenolate base results in the formation of a dimeric motif that contains a new Fe–C(methine) bond resulting from coordination of the deprotonated methylene unit to an adjacent iron center. This effective second carbanion in the ligand framework was demonstrated to drive heterolytic H₂ activation across the Fe(ii) center. However, this process results in reductive elimination and liberation of the ligand to extrude a lower-valent Fe–carbonyl complex. Through a series of isotopic labelling experiments, structural characterization (XRD, XAS), and spectroscopic characterization (IR, NMR, EXAFS), a mechanistic pathway is presented for H₂/hydride-induced loss of the organometallic acyl unit (i.e. pyCH₂–C O → pyCH₃+C O). The known reduced hydride species [HFe(CO)₄]⁻ and [HFe₃(CO)₁₁]⁻ have been observed as products by ¹H/²H NMR and IR spectroscopies, as well as independent syntheses of PNP[HFe(CO)₄]. The former species (i.e. [HFe(CO)₄]⁻) is deduced to be the actual hydride transfer agent in the hydride transfer reaction (nominally catalyzed by the title compound) to a biomimetic substrate ([^TolIm](BAr^F) = fluorinated imidazolium as hydride acceptor). This work provides mechanistic insight into the reasons for lack of functional biomimetic behavior (hydride transfer) in acyl(methylene)pyridine based mimics of [Fe]-hydrogenase.

We report the synthesis and reactivity of a model of [Fe]-hydrogenase derived from an anthracene-based scaffold that includes the endogenous, organometallic acyl(methylene) donor.     

Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia synthesis

Photocatalytic N₂ fixation to NH₃via defect creation on TiO₂ to activate ultra-stable N N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N₂ preferentially adsorbs on phase-selective defect sites on TiO₂ in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (A_d) preferentially exhibit higher N₂ adsorption ability with a reduced energy barrier for a potential-determining-step (*N₂ to NNH*) than the disordered rutile (R_d) phase of TiO₂. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/ordered-rutile TiO₂ photocatalyst (Na-A_d/R_o) by sodium-amine treatment of P25-TiO₂ under ambient conditions, which exhibits an efficient NH₃ formation rate of 432 μmol g⁻¹ h⁻¹, which is superior to that of any other defect-rich disordered TiO₂ under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N₂ chemisorption on the defect sites of Na-A_d with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with R_o enable substantially enhanced N₂ fixation.

This work highlights the importance of a rational design for more energetically suitable nitrogen reduction reaction routes and mechanisms by regulating the electronic band structures with phase-selective defect sites.     

Facile synthesis of an ambient stable pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b′]dipyrrole dianion: from serendipity to design

The stability of singly or multiply negatively charged π-conjugated organic compounds is greatly influenced by their electronic delocalization. Herein, we report a strategic methodology for isolation of a mysterious compound. The isolated compounds, a pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b′]dipyrrole dianion, were highly stable under ambient conditions due to high delocalization of the negative charge over multiple electron deficient C N groups and pyrene π-scaffolds and allowed purification by column chromatography. To our knowledge, this is the first report on TCNE type reductive condensation of malononitrile involving pyrene di- and tetraone and formation of pyrenopyrrole. All compounds were characterized by spectroscopic methods and X-ray crystallography. A UV-vis spectroscopic study shows an intense low energy absorption band with a large absorption coefficient (ε).

An ambient stable pyreno[4,5-b]pyrrole monoanion and pyreno[4,5-b:9,10-b′]dipyrrole dianion have been isolated and characterized, showing a low energy intense absorption band with the absorption coefficient reaching 7.1 × 10⁴ dm³ mol⁻¹ cm⁻¹.     

Tri-insertion with dearomatization of terminal arylalkynes using a carborane based frustrated Lewis pair template

Intramolecular vicinal Frustrated Lewis Pairs (FLPs) have played a significant role in the activation of small molecules, and their stabilities and reactivities are found to strongly depend on the nature of the bridging units. This work reports a new carborane based FLP, 1-PPh₂-2-BPh₂-1,2-C₂B₁₀H₁₀ (2), which reacts with an equimolar amount of p-R₂NC₆H₄C CH (R = Me, Et, Ph) at room temperature to give C C triple bond addition products 1,2-[PPh₂C(R₂NC₆H₄) CHBPh₂]-1,2-C₂B₁₀H₁₀ (3) in high yields. Compounds 3 react further with two equiv. of p-R₂NC₆H₄C CH (R = Me, Et) at 60–70 °C to give unprecedented stereoselective tri-insertion products, 3,3a,6,6a-tetrahydronaphtho[1,8a-b]borole tricycles (4), in which one of the aryl rings from arylacetylene moieties has been dearomatized with the formation of four stereocenters including one quaternary carbon center. It is noted that the phosphine unit functions as a catalyst during the reactions. After trapping and structural characterization of a key intermediate, a reaction mechanism is proposed, involving sequential alkyne insertion and 1,2-boryl migration.

A carborane based frustrated Lewis pair enables tri-insertion with dearomatization of arylalkynes, forming unprecedented products, borole tricycles, with the construction of four stereocenters including one quaternary carbon center in one process.     

Unexpected formation of 1,2- and 1,4-bismethoxyl Sc3N@Ih-C80 derivatives via regioselective anion addition: an unambiguous structural identification and mechanism study

An attempt to achieve heterocyclic cycloadducts of Sc₃N@I_h-C₈₀via reaction with Ph₂C O, PhC CPh or PhC N in the presence of tetrabutylammonium hydroxide (TBAOH) stored in CH₃OH led to the formation of the unexpected bismethoxyl adducts of Sc₃N@I_h-C₈₀ (1 and 2). Further studies reveal that TBAOH in CH₃OH can boost the CH₃O⁻ addition efficiently, regardless of the presence of other reagents. Single-crystal X-ray diffraction results firmly assign the molecular structures of 1 and 2 as respective 1,4- and 1,2-bismethoxyl adducts, and reveal unusual relationships between the internal Sc₃N cluster and the addition modes, in addition to the unusual packing mode in view of the orientation of the methoxyl groups. Electrochemical results demonstrate smaller electrochemical gaps for 1 and 2, relative to that of Sc₃N@I_h-C₈₀, confirming their better electroactive properties. Finally, a plausible reaction mechanism involving anion addition and a radical reaction was proposed, presenting new insights into the highly selective reactions between the methoxyl anion and metallofullerenes. 1 and 2 represent the first examples of methoxyl derivatives of metallofullerenes. This work not only presents a novel and facile strategy for the controllable synthesis of alkoxylated metallofullerene derivatives, but also provides new non-cycloadducts for the potential applications of EMFs.

An attempt to achieve heterocyclic cycloadducts of Sc₃N@I_h-C₈₀via reaction with Ph₂C O, PhC CPh or PhC N in the presence of tetrabutylammonium hydroxide (TBAOH) stored in CH₃OH led to the formation of the unexpected bismethoxyl adducts of Sc₃N@I_h-C₈₀ (1 and 2).     

The power of trichlorosilylation: isolable trisilylated allyl anions,allyl radicals,and allenyl anions

Treatment of hexachloropropene (Cl₂C C(Cl)–CCl₃) with Si₂Cl₆ and [nBu₄N]Cl (1 : 4 : 1) in CH₂Cl₂ results in a quantitative conversion to the trisilylated, dichlorinated allyl anion salt [nBu₄N][Cl₂C C(SiCl₃)–C(SiCl₃)₂] ([nBu₄N][1]). Tetrachloroallene Cl₂C C CCl₂ was identified as the first intermediate of the reaction cascade. In the solid state, [1]⁻ adopts approximate C_s symmetry with a dihedral angle between the planes running through the olefinic and carbanionic fragments of [1]⁻ of C C–Si//Si–C–Si = 78.3(1)°. One-electron oxidation of [nBu₄N][1] with SbCl₅ furnishes the distillable blue radical 1˙. The neutral propene Cl₂C C(SiCl₃)–C(SiCl₃)₂H (2) was obtained by (i) protonation of [1]⁻ with HOSO₂CF₃ (HOTf) or (ii) H-atom transfer to 1˙ from 1,4-cyclohexadiene. Quantitative transformation of all three SiCl₃ substituents in 2 to Si(OMe)₃ (2^OMe) or SiMe₃ (2^Me) substituents was achieved by using MeOH/NMe₂Et or MeMgBr in CH₂Cl₂ or THF, respectively. Upon addition of 2 equiv. of tBuLi, 2^Me underwent deprotonation with subsequent LiCl elimination, 1,2-SiMe₃ migration and Cl/Li exchange to afford the allenyl lithium compound Me₃Si(Li)C C C(SiMe₃)₂ (Li[4]), which is an efficient building block for the introduction of Me, SiMe₃, or SnMe₃ (5) groups. The trisilylated, monochlorinated allene Cl₃Si(Cl)C C C(SiCl₃)₂ (6), was obtained from [nBu₄N][1] through Cl⁻-ion abstraction with AlCl₃ and rearrangement in CH₂Cl₂ (1˙ forms as a minor side product, likely because the system AlCl₃/CH₂Cl₂ can also act as a one-electron oxidant).

Treatment of hexachloropropene (Cl₂C C(Cl)–CCl₃) with Si₂Cl₆ and [nBu₄N]Cl (1 : 4 : 1) in CH₂Cl₂ results in a quantitative conversion to the trisilylated, dichlorinated allyl anion salt [nBu₄N][Cl₂C C(SiCl₃)–C(SiCl₃)₂] ([nBu₄N][1]).     

Dynamic supramolecular self-assembly of platinum(ii) complexes perturbs an autophagy–lysosomal system and triggers cancer cell death

Self-assembly of platinum(ii) complexes to form supramolecular structures/nanostructures due to intermolecular ligand π–π stacking and metal–ligand dispersive interactions is widely used to develop functional molecular materials, but the application of such non-covalent molecular interactions has scarcely been explored in medical science. Herein is described the unprecedented biological properties of platinum(ii) complexes relevant to induction of cancer cell death via manifesting such intermolecular interactions. With conjugation of a glucose moiety to the planar platinum(ii) terpyridyl scaffold, the water-soluble complex [Pt(tpy)(C CArOGlu)](CF₃SO₃) (1a, tpy = 2,2′:6′,2′′-terpyridine, Glu = glucose) is able to self-assemble into about 100 nm nanoparticles in physiological medium, be taken up by lung cancer cells via energy-dependent endocytosis, and eventually transform into other superstructures distributed in endosomal/lysosomal and mitochondrial compartments apparently following cleavage of the glycosidic linkage. Accompanying the formation of platinum-containing superstructures are increased autophagic vacuole formation, lysosomal membrane permeabilization, and mitochondrial membrane depolarization, as well as anti-tumor activity of 1a in a mouse xenograft model. These findings highlight the dynamic, multi-stage extracellular and intracellular supramolecular self-assembly of planar platinum(ii) complexes driven by modular intermolecular interactions with potential anti-cancer application.

Self-assembly of platinum(ii) glycosylated arylacetylide gave transformable superstructures upon enzymatic action in cellulo, leading to perturbation of an autophagy-lysosomal system and cancer cell death.     

Diverse ring-opening reactions of rhodium η4-azaborete complexes

Sequential treatment of [Rh(COE)₂Cl]₂ (COE = cyclooctene) with PⁱPr₃, alkyne derivatives and ^tBuN BMes (Mes = 2,4,6-trimethylphenyl) provided functionalized rhodium η⁴-1,2-azaborete complexes of the form (η⁴-azaborete)RhCl(PⁱPr₃). The scope of this reaction was expanded to encompass alkynes with hydrogen, alkyl, aryl, ferrocenyl, alkynyl, azaborinyl and boronate ester substituents. Treatment of these complexes with PMe₃ led to insertion of the rhodium atom into the B–C bond of the BNC₂ ring, forming 1-rhoda-3,2-azaboroles. Addition of N-heterocyclic carbenes to azaborete complexes led to highly unusual rearrangements to rhodium η²,κ¹-allenylborylamino complexes via deprotonation and C–N bond cleavage. Heating and photolysis of an azaborete complex also led to rupture of the C–N bond followed by subsequent rearrangements, yielding an η⁴-aminoborylallene complex and two isomeric η⁴-butadiene complexes.

Rhodium η⁴-azaborete complexes can be transformed into a variety of species with ring-opened, BN-containing ligands by treatment with Lewis bases.