Search

Semiconductor conductivities depend largely on the crystal structures and the associated electronic structures. If the electronic structures can be switched reversibly in the same crystal structure, then a drastic conductivity change may be controllable. The effect of electron transfer (ET) on semiconductor conductivity remained elusive so far. In this work, a series of two pillared inorganicorganic hybrid photochromic semiconductors (PSCs), [(CQ)Pb

Hypersensitive regulation of cellular hypoxic response relies on cooperative displacement of one disordered protein (HIF-1α) by another disordered protein (CITED2) from the target in a negative feedback loop. Considering the weak intramolecule coupling in disordered proteins, the molecular mechanism of high cooperativity in the molecular displacement event remains elusive. Herein, we show that disordered proteins utilize a "self-effected allostery" mechanism to achieve high binding cooperativity. Different from the conventional allostery mechanisms shown by many structured or disordered proteins, this mechanism utilizes one part of the disordered protein as the effector to trigger the allosteric coupling and enhance the binding of the remaining part of the same disordered protein, contributing to high cooperativity of the displacement event. The conserved charge motif of CITED2 is the key determinant of the molecular displacement event by serving as the effector of allosteric coupling. Such self-effected allostery provides an efficient strategy to achieve high cooperativity in the molecular events involving disordered proteins.

Achieving large phase-matchable (PM) nonlinear optical (NLO) efficiency and high laser-induced damage threshold (LIDT) in an infrared second-order NLO (IR NLO) material is the most crucial technica...

It remains a challenge to develop UV nonlinear optical (NLO) crystals that can achieve a desirable trade-off on UV absorption edge, second harmonic generation (SHG), and birefringence. Here we report a thiosulfate UV NLO crystal of a 2D van der Waals layered structure, [C(NH2)3]2SO3S. Remarkably, this thiosulfate realizes the desired trade-off, with a short absorption edge of 254 nm, a strong SHG response of approximately 2.8 times that of the benchmark KH2PO4, and a sufficient birefringence of 0.073 at the wavelength of 546 nm. In addition, it exhibits strong in-plane anisotropy of the SHG intensity. According to the first-principles calculations, the non-π-conjugated [SO3S]2- anion is the dominant SHG functional gene, while the π-conjugated [C(NH2)3]+ cation serves as the functional gene of birefringence. This is different from common UV NLO materials whose functionals of SHG and birefringence are the same. These findings indicate that combining different function genes may be an effective strategy to develop outstanding NLO materials with the desirable property trade-off.

Second-order nonlinear optical (NLO) switchable materials are eliciting increased interest because of their widespread optical applications. The stringent requirements of NLO efficiency, laser-indu...

Ammonia is among the available sustainable fuels for humans in the future. Electrochemical nitrogen fixation, which is a promising ammonia synthesis method, can achieve artificial N₂ fixation at room temperature and pressure. We report that 5% Co₄N/Co₂C@rGO is a high-efficiency nitrogen reduction reaction electrocatalyst for ammonia synthesis under ambient conditions. The catalyst obtains high NH₃ yield (24.12 μg h–¹ mgcₐₜ–¹) and Faradaic efficiency (24.97%) at −0.1 V (vs RHE) in 0.1 M HCl. The addition of graphene reduces CoN to Co₂C and Co₄N. A high ratio of Co–C bonds improves NRR performance. The excellent performance of the catalyst is attributed to the high proportion of pyridine N and pyrrole N. Data analysis results show that the NRR on the surface of Co₄N adopts a favorable Mars–van Krevelen reaction mechanism. Moreover, the Co₂C(101) crystal plane is more conducive to NRR.

Exploration of a new nonlinear optical (NLO)-active functional motif is important in the rational design of promising infrared (IR) NLO materials. Compared with typical tetrahedral MQ4 (M = IIB, II...

Noncentrosymmetry (NCS) is a prerequisite for second-order nonlinear optical (NLO) materials. In this work, a new polycation-substitution-induced centrosymmetry (CS)-to-NCS transformation strategy was applied in CS RbGaS2, affording two novel NCS salt-inclusion chalcogenides: [ABa2Cl][Ga4S8] (A = Rb, 1; Cs, 2). Remarkably, they exhibit the key merits of both Vis and IR NLO candidates, including strong phase-matchable second harmonic generation intensities (10.4-15.3 × KH2PO4 at 1064 nm; 0.9-1.0 × AgGaS2 at 1910 nm), high laser-induced damage thresholds (11-12 × AgGaS2), and a wide transparent window. Their prominent NLO performances originate from the orderly packing of T2-supertetrahedral Ga4S10 motifs resulting from the template effect of acentric polycation [ClA2Ba3]7+. The CS-to-NCS transformation first realized by polycation-substitution-induced NLO-functional motif ordering provides an effective approach for designing new NLO materials.

Currently, a variety of elastomers with a self-healing capacity and reprocessability have been developed by dynamic chemistry to extend the service life, increase the reliability of polymeric mater...

Herein, a novel three-dimensional (3D) DNA nanomachine with high walking efficiency via free DNA walker movement on biomimetic lipid bilayers supported by hard silica@CdTe quantum dots (SiO2@CdTe) was constructed for ultrasensitive fluorescence detection of microRNA. The synthesized SiO2@CdTe nanoparticles were adopted as the fluorescence indicator and spherical carrier of lipid bilayers, and then the DNA substrates were anchored on lipid bilayers with biomimetic fluidity through the cholesterol-lipid interaction. Once target microRNA-141 interacted with the 3D DNA nanomachine to release cholesterol labeled arm (Chol-arm), the Chol-arm could generate a series of strand displacement reactions by moving freely on the lipid bilayers, resulting in the releasement of numerous quenchers from the SiO2@CdTe nanoparticles and inducing a strong fluorescence signal. Impressively, compared with traditional 3D DNA nanomachine conjugating DNA substrates on hard surfaces (such as gold or silica) with limited reactivity, the proposed biomimetic 3D DNA nanomachine not only immobilized DNA substrates rapidly and effectively but also kept it with a favorable fluidity, which significantly enhanced the walking efficiency. As expected, the biomimetic 3D DNA nanomachine for fluorescence detection of microRNA-141 exhibited an excellent performance with a detection limit of 0.21 pM and presented promising properties in cell lysate detection and intracellular imaging. Thus, the described biomimetic 3D DNA nanomachine provided a novel avenue for sensitive detection of biomolecules, which could be useful for bioanalysis and early clinical diagnoses of disease.

Polymeric graphitic carbon nitride (g-CN) has emerged as a promising metal-free photocatalyst; however, the polymerization process is still poorly understood, and the synthesized g-CN shows a struc...

This work details a novel polyurethane liquid crystal elastomer (PULCE) with exchangeable carbamate functional groups that enable programming of a uniformly aligned monodomain sample through the ap...

Despite extensive research on transition metal-catalyzed Fujiwara–Moritani type C–H olefinations, the alkenes used in these transformations are still mainly limited to active acrylate esters and styrenes. Selective aryl C–H olefination with electron-rich alkenes is recognized as a challenging issue. We herein report that simple and readily accessible electron-deficient [CpRh(III)] and [CpCF3Rh(III)] (CpCF3 = C5Me4CF3) complexes are powerful catalysts for dehydrogenative arylation of electron-rich alkenes, including vinyl acetates, enamides, and vinyl ethers. Employing an electron-withdrawing Cp or CpCF3 ligand instead of the privileged Cp* (C5Me5) ligand not only can facilitate the electrophilic aryl C–H rhodation but also can lower the olefin insertion barrier. Both electron-withdrawing and electron-donating directing groups such as -CONR2 and -NHAc could be employed in these reactions, which provides convenient routes toward a series styryl acetates, N-acetylindoles, and aryl methyl ketones.

Tetra(4-pyridyl)porphyrin (TPyP)-functionalized thermosensitive ionic microgels (TPyP5-MGs) were synthesized by a two-step quaternization method. The obtained TPyP5-MGs have a hydrodynamic radius of about 189 nm with uniform size distribution and exhibit thermosensitive character. The TPyP5-MG microgel suspensions can optically respond to trace Pb2+ ions in aqueous solution with high sensitivity and selectivity over the interference of other 19 species of metal ions (Yb3+, Gd3+, Ce3+, La3+, Bi3+, Ba2+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, K+, Na+, Li+, Al3+, Cu2+, Ag+, Cd2+, and Fe3+) by using UV–visible spectroscopy. The sensitivity of TPyP5-MGs toward Pb2+ can be further improved by increasing the solution temperature. The limit of detection for TPyP5-MG microgel suspensions in the detection of Pb2+ in aqueous solution at 50 °C is about 25.2 nM, which can be further improved to be 5.9 nM by using the method of higher order derivative spectrophotometry and is much lower than the U. S. EPA standard for the safet...

Recently, charge transfer (CT) interactions have received attention for the fabrication of supramolecular architectures due to their inherent compatibilities, directional nature and solvent tolerance. In this study, we report a shape-memory dynamic network constructed by the CT interaction between π-electron-rich naphthalene embedded in poly(ethylene glycol) (PEG-Np) and π-electron-poor six-arm methyl-viologen-ended poly(ethylene glycol) (6PEG-MV), which was verified by ultraviolet–visible spectroscopy (UV–vis), fluorescence spectra and swelling tests. Interestingly, the mechanical properties of this CT complex were dramatically enhanced compared with the control without CT interaction. Moreover, the excellent shape-memory effect (SME) was realized due to the good crystallization of the PEG segment and stable netpoints based on the CT interaction. In addition, as we expected, this supramolecular polymer network is self-healable and reprocessable.

Two new infrared (IR) nonlinear optical (NLO) sulfides, Na2Ga2GeS6 and Na2Ga2SnS6, were obtained by mixing different typical NLO-active motifs GaS4 and GeS4/SnS4 in the alkali metal-containing system. The IR NLO sulfides present laser-induced damage thresholds that are 18.1 and 17.9 times that of the reference AgGaS2 (AGS) and second-harmonic generation efficiencies that are 0.8 and 1.1 times that of AGS. These properties originate from the GaS4, GeS4, and SnS4 tetrahedral blocks in the structures of the sulfides. Both compounds also exhibit a broad transparency range and type-I phase-matching behavior, which support their high potential in high-power laser applications. This work sheds new light on the development of promising mid-IR NLO materials by combining different NLO-active motifs.

Advancement in explosive systems toward miniaturization and enhanced safety has prompted the development of primary explosives with powerful detonation performance and relatively low sensitivities. Energetic coordination polymers (ECPs) as a new type of energetic materials have attracted wide attention. However, regulating the energetic characters of ECPs and establishing the relationship between structure and energetic property remains great challenges. In this study, two isomorphic 2D π-stacked solvent-free coordination polymers, [M(N3)2(atrz)]n (M = Co 1, Cd 2; atrz = 4,4′-azo-1,2,4-triazole), were hydrothermally prepared and structurally characterized by X-ray diffraction. The two compounds exhibit reliable stabilities, remarkable positive enthalpies of formation, and prominent heats of detonation. The enthalpy of formation of 1 is 4.21 kJ·g–1, which is higher than those of all hitherto known primary explosives. Repulsive steric clashes between the sensitive azide ions in 1 and 2 influence the mechani...

Two new polar polyselenides Rb4Ge4Se12 (1) and Cs4Ge4Se12 (2) with rarely reported dimeric [Ge2Se4(μ-Se2)]4− units were synthesized. They present large second-harmonic generation (SHG) intensities of 7.5 and 6.5 times that of the benchmark AgGaS2 with type I phase-matching behavior, high laser induced damaged thresholds, wide transmission region and congruently melting behavior, making them excellent candidates for IR nonlinear optical (NLO) applications. The SHG functional motifs of both compounds are determined to be [Ge2Se4(μ-Se2)]4− unit by time-dependent density functional theory calculation, which further reveals that charge transfers from the lone pairs of terminal Se atoms to the five σ* orbitals of five-membered ring Ge2Se3 have a predominant contribution to the total SHG effect.

Herein, we report a novel thermal/photoresponsive shape-memory polyurethane network with a pendant azobenzene group by utilizing its anisotropic–isotropic phase transitions and photoresponsive feature concurrently. To achieve this goal, the side-chain liquid crystalline polyurethane networks based on the pendant azobenzene group [SCLCPU(AZO)-Ns] were developed in a well-defined architecture. The smectic C nature of an LC phase in the polyurethane networks was confirmed by differential scanning calorimetry, polarized optical microscopy, and one-dimensional and two-dimensional wide-angle X-ray diffraction. The well-defined architecture-made SCLCPU(AZO)-N displays two distinct transition temperatures (Ttrans) (Tg and Tcl), with a difference of about 40 °C. Consequently, the excellent triple-shape-memory effect in this network was demonstrated by cyclic thermomechanical analysis. By making full use of the trans–cis photoisomerization of azobenzene, the reversible bending and unbending behaviors were realized ...

Developing excellent infrared nonlinear optical (NLO) materials is challenging because of the incompatibility between a large second harmonic generation (SHG) efficiency and a high laser-induced damage threshold (LIDT). Here, we report three NLO chalcogenides, namely, Na2In4SSe6 (1), NaGaIn2Se5 (2), and NaIn3Se5 (3), whose crystal structures consist of supertetrahedral, superpentahedral, and superoctahedral chalcogenide clusters. Importantly, they exhibit SHG responses 7.0-, 2.1-, and 0.3-fold larger than and LIDTs 5.8-, 6.4-, and 10.7-fold higher than those of AgGaS2, respectively, almost achieving balance between large SHG efficiencies and high LIDTs. Theoretical calculations and structural analysis reveal that the enhanced SHG responses can be attributed to the superpolyhedral chalcogenide clusters. The high LIDTs can be ascribed to their small thermal expansion anisotropy. These findings may provide useful insights into the development of infrared NLO materials with superpolyhedron-built structures.

Quaternary metal thiophosphates containing second-order Jahn–Teller distorted d10 Ag+ and lone-pair cations, Ag3Bi(PS4)2 (1), Ag7Sn(PS4)3 (2), and Ag7Pb(PS4)3 (3), were obtained by solid-state synthesis. The structural frameworks of 2 and 3 feature an infinite 1-D interchiral double helix ∞1(Ag3P2S11), which is rare in inorganic compounds. Compound 3 undergoes a significant first-order structural phase transition from monoclinic to hexagonal at ∼204 °C. This can be ascribed to the significant mismatch in the expansion coefficients between Pb–S (Ag–S) and P–S bonds evaluated by bond valence theory. The three compounds are Ag+ ionic conductors, and Ag+ ion migration pathways are proposed by calculating maps of low bond valence mismatch. Moreover, the optical properties of the three compounds were studied, and electronic structure calculations were performed. The combination of second-order Jahn–Teller distorted d10 cation and lone-pair cation provides a new strategy to explore new metal thiophosphates with ...

Two new phases in the Ag–Cd–P–S system containing two second-order Jahn–Teller (SOJT) distorted d10 cations (Cd2+ and Ag+), namely, Ag2Cd(P2S6) (1) and AgCd3(PS4)S2 (2), are obtained via medium-temperature solid-state synthesis. Compound 1 exhibits a two-dimensional layered structure and undergoes a first-order structural phase transition at approximately 280 °C. This outcome can be ascribed to the significant mismatch in the expansion coefficients between Cd–S (Ag–S) and P–P (P–S) bonds evaluated through bond valence theory. The three-dimensional non-centrosymmetric (NCS) framework of 2 is constructed by two types of tetrahedral layers consisting of corner-shared CdS4, AgS4, and PS4 tetrahedra. Compound 2 exhibits second harmonic generation (SHG) intensity of 0.45 times that of commercial AgGaS2 (AGS) at a laser irradiation of 1.85 μm and an optical band gap of 2.56 eV, and no intrinsic vibrational absorption of chemical bonds is observed in the range of 2.5–18.2 μm. Both phase transition in 1 and SHG pr...

Treatment of OsCl2(PPh3)3 with HC≡CAr (Ar = Ph, p-tolyl) produced the η3-allenylcarbene complexes OsCl2(═CAr-η2-CH═C═CHAr)(PPh3)2. Reactions of the η3-allenylcarbene complexes with gold alkynyls Au(C≡CR)(PPh3) (R = Ph, p-tolyl, TMS, nBu, CH(OEt)2) or copper(I) alkynyls Cu(C≡CR) (R = Ph, TMS) in the presence of HNEt3Cl produced the osmabenzynes Os{≡CC(R)═C(CH2Ar)CH═CAr}Cl2(PPh3)2. Computational studies suggest that the osmabenzynes are formed through electrocyclization of osmium alkynyl-allenylcarbene intermediates followed by protonation with HNEt3Cl.

A copper-catalyzed aminobenzannulation of (o-alkynyl)arylketones with amines has been developed. This method features the use of a cheap copper catalyst, the facile annulation involving various amines, and the good functional group tolerance.

The copper-catalyzed regioselective cross-dehydrogenative coupling of N-pyrimidylindoles with benzylic C(sp(3))-H bonds has been developed. Di-tert-butyl peroxide was employed as a mild oxidant, and benzaldehyde proved to be an effective additive. This reaction provides a direct and pratical route to a variety of 2-benzylindoles.

The first examples of half-sandwich boratabenzene ruthenium complexes have been prepared and well-characterized. Treatment of RuCl2(PPh3)3 with the anionic boratabenzene ligands C5H5BORNa (R = Et, Me) produced the B-alkoxy complexes (η6-C5H5BOR)RuCl((PPh3)2 (R = Et, 1a; Me, 1b), while the reaction of RuCl2(PPh3)3 with the neutral borabenzene–PPh3 adduct C5H5BPPh3 led to the formation of the dinuclear complex (μ2-η6,η6-C5H5BOBC5H5)[RuCl(PPh3)2]2 (2), with an oxo-bis(boratabenzene) bridging ligand connected by the B–O–B linkage. The B-hydroxy complex (η6-C5H5BOH)RuCl(PPh3)2 (3) was obtained from the nucleophilic substitution of complexes 1a, 1b, or 2 with water at the boron atoms, and the complexes 1a, 1b, 2, and 3 could interconvert through the nucleophilic substitution reactions. While the reaction of 1a with phenylacetylene did not successfully afford the vinylidene complex as expected, reactions of 1a with terminal ω-alkynols HC≡C(CH2)nCH(R)OH (R = H, n = 1, 2; R = Me, n = 1) proceeded smoothly to provi...

The activation of C(sp3)–H bonds is challenging, due to their high bond dissociation energy, low proton acidity, and highly nonpolar character. Herein we report a unique gold(I)–silver(I) oxo cluster protected by hemilabile phosphine ligands [OAu3Ag3(PPhpy2)3](BF4)4 (1), which can activate C(sp3)–H bonds under mild conditions for a broad scope of methyl ketones (RCOCH3, R = methyl, phenyl, 2-methylphenyl, 2-aminophenyl, 2-hydroxylphenyl, 2-pyridyl, 2-thiazolyl, tert-butyl, ethyl, isopropyl). Activation happens via triple deprotonation of the methyl group, leading to formation of heterometallic Au(I)–Ag(I) clusters with formula RCOCAu4Ag4(PPhpy2)4(BF4)5 (PPhpy2 = bis(2-pyridyl)phenylphosphine). Cluster 1 can be generated in situ via the reaction of [OAu3Ag(PPhpy2)3](BF4)2 with 2 equiv of AgBF4. The oxo ion and the metal centers are found to be essential in the cleavage of sp3 C–H bonds of methyl ketones. Interestingly, cluster 1 selectively activates the C–H bonds in −CH3 rather than the N–H bonds in −NH2 ...

Treatment of the osmabenzyne complex Os{≡C-C(SiMe3)═C(CH3)-C(SiMe3)═CH−}Cl2(PPh3)2 with Mo(CO)6 in refluxing benzene produced the η5-chlorocyclopentadienyl complex Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) and Mo(CO)5(PPh3). A computational study suggests that the chlorocyclopentadienyl complex is most likely produced via the carbene intermediate Os{═C(C(SiMe3)═C(CH3)-C(SiMe3)═CH−)}Cl2(CO)(PPh3) formed by a migratory insertion reaction of the osmabenzyne complex Os{≡C-C(SiMe3)═C(CH3)-C(SiMe3)═CH}Cl2(CO)(PPh3). DFT calculations show that the relative thermal stability of metallabenzynes Os(≡C-CH═CHCH═CH)Cl2(L)2 and the corresponding isomeric carbene complexes Os{═C(−CH═CHCH═CH−)}Cl2(L)2 as well as the chlorocyclopentadienyl complexes Os(η5-C5ClH4)Cl(L)2 (L = CO, phosphine, pyridine, amine) is strongly dependent on ligand L.

National Natural Science Foundation of China [20925208, 21174115, 21272193]; Natural Science Foundation of Fujian Province [2011J05031]; National Basic Research Program of China [2012CB821600]

National Basic Research Program of China [2012CB821600]; National Natural Science Foundation of China [20925208, 21174115, 21272193]; Changjiang Scholars and Innovative Research Team in University

In our efforts to probe the reaction mechanism of the endo cycloisomerization of alkynols catalyzed by the complex [Ru(N3P)(OAc)](BPh4) (1; NP3 = N,N-bis[(pyridin-2-yl)methyl][2-(diphenylphosphino)phenyl]methanamine), the reactions of 1 with alkynes were investigated. Several complexes related to intermediates in the catalytic reactions were isolated and characterized. In the presence of DIPEA (N,N-diisopropylethanamine), complex 1 reacted with 3-butyn-1-ol to afford the Ru−oxocyclocarbene complex {Ru(N3P)[═C(CH2)3O](OAc)}(BPh4) (4). Under anhydrous conditions, the reaction of complex 1 with tert-butylacetylene afforded [Ru(N3P)(η3-tBuC≡CC═CHBut)](BPh4) (8). In the presence of water, the reaction of complex 1 with tert-butylacetylene afforded [Ru(N3P)(CO)(η1-CH2But)](BPh4) (13). All the reactions are likely to proceed through ruthenium vinylidene intermediates. These results support that ruthenium vinylidene complexes are involved as the key intermediates in the cycloisomerization of alkynols catalyzed by...

A 3D metal-organic framework (MOF), [Zn(BPHY)(SA)]n (1; BPHY = 1,2-bis(4-pyridyl)hydrazine, H2SA = succinic acid), which crystallizes in a noncentrosysmmetric space group (Cc), has been solvothermally obtained and testified to be a good nonlinear-optical material with the largest second-harmonic-generation response among the known MOFs based on sysmmetric ligands and high stability. Ultraviolet-to-visible tunable emission for 1 is observed.

National Science Foundation of China [20925208, 20872123, 20772100]; Program for New Century Excellent Talents in University of China [NCET-08-0471]; Program for New Century Excellent Talents in Fujian Province University ; Department of Science & Technology of Fujian Province [2007F3095]

Treatment of HC≡CCH(OH)CH═CH2 with [IrHCl(CO)(PPh3)3]BF4 at room temperature afforded an iridacyclohexadiene, [Ir(CH═C(PPh3)CH═CHCH2)Cl(CO)(PPh3)2]BF4 (1). The reactivity of complex 1 had been investigated. Reaction of 1 with 1 equiv of bromine produced an iridacyclopentadiene, [Ir(CH═C(PPh3)CH═C(CH2Br))Cl(CO)(PPh3)2]BF4 (2). When excess bromine was used, iridacyclopentadiene 2 underwent subsequent intramolecular C(sp2)−C(sp3) coupling between the exocyclic −CH2Br group and a phenyl of the PPh3 ligand, leading to the formation of a fused iridacycle complex, [Ir(CH═C(PPh3)C(Br)═C(CHBr))(P(C6H4)Ph2)Cl(CO)PPh3]Br3 (3). A mechanism for the formation of complex 3 starting from 1 was proposed, in which the process involved a triple C−H activation as well as a rare C(sp2)−C(sp3) reductive elimination.

Ring-expansion reactions of the five-membered osmafuran Os{═CHC(PPh3)═C(O) OEt}Cl2(PPh3)2 (1) via alkyne insertion have been investigated, which lead to the formation of several nine-membered osmacycles. Reaction of 1 with PhC≡CH gives the nine-membered complexes Os{═CPhCH═CPh-η2-CH═CHC(PPh3)═C(O)OEt}Cl2(PPh3) as a mixture of a couple of isomers 2a and 2b with different disposition of the two chloride ligands on the metal centers. The reaction involves a head-to-tail double insertion of PhC≡CH into osmacycle 1 via [2 + 2] cycloaddition process, which is relevant to the polymerization of alkynes by metathesis reaction. Treatment of the mixture of 2a and 2b with PMe3 gives selectively Os{═CPhCH═CPh-η2-CH═CHC(PPh3)═C(O)OEt}Cl2(PMe3) (3), the PMe3-substituted counterpart of 2a. These complexes might serve as the intermediates for alkyne polymerization which are stabilized by the coordination of internal olefin. Heating the mixture of 2a and 2b in CHCl3 under reflux gives complex Os{η2-CHPh═CHCPh═CHCC(PPh3)C(O...