Probing Site Cooperativity of Frustrated Phosphine/Borane Lewis Pairs by a Polymerization Study

The first highly active phosphine (P)/borane (B) Lewis pair polymerization is promoted unexpectedly by P–B adducts. The P and B site cooperativity is essential for achieving effective polymerization, as shown by this study examining the reactivity of a library of P/B Lewis pairs toward polymerization of a renewable acrylic monomer

Highly Active Half-Metallocene Yttrium Catalysts for Living and Chemoselective Polymerization of Allyl Methacrylate

Highly active half-metallocene amidinate yttrium catalysts for chemoselective and living polymerization of allyl methacrylate are reported. The living characteristics of allyl methacrylate polymerization have been proved by three sets of experiments. The generated polymers exhibit good solubility in DMF, well-controlled molecular weights, and narrow molecular weight distributions (<i><i>Đ</i></i> < 1.10). The kinetic studies revealed that the catalyst systems follow a living monometallic coordination–addition polymerization mechanism. The present study is first example for rare earth metal-catalyzed living coordination–addition polymerization of polar divinyl monomers

Intrinsic interfacial dynamic engineering of zincophilic microbrushes via regulating Zn deposition for highly reversible aqueous zinc ion battery

Aqueous rechargeable zinc ion batteries are promising efficient energy storage systems due to remarkable safety and satisfactory capacity. However, zinc metal anode instability including dendrite growth and side reactions severely hinders widespread applications. Herein, zincophilic microbrushes have been in situ anchored on zinc plates through simple freeze-drying and mild reduction of graphene oxide, successfully overcoming these thorny issues. By introducing suitable oxygen-containing groups, the microbrushes exhibit a good affinity for zinc ions, thereby providing sufficient depositing sites, promoting zinc plating and stripping during cycling, and suppressing side reactions. The delicate zincophilic microbrushes can not only function as protective layer to guide the deposition of zinc ions, but also act as high-speed pathways to redistribute the zinc ion flux for rapid kinetics. Consequently, the microbrushes-covered zinc anode displays long lifespan and good durability, whenever in symmetric cell or full battery tests. This work paves a feasible bridge to design advanced aqueous anodes by architecting both structures and compositions of metal coverings.Ministry of Education (MOE)This work is financially supported by the National Natural Science Foundation of China (21905133, 52174284, 52172204, and 51872139) and MOE AcRF Tier 1 grant no. 2020-T1-001-031 (Singapore)

Spontaneous Resolution of Evans–Showell-Type Polyoxometalates in Constructing Chiral Inorganic–Organic Hybrid Architectures

Six new hybrid compounds based on [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanion, (4-H₂pya)₆Co₂Mo₁₀H₄O₃₈·10H₂O <b>1</b> (4-Hpya =3-(4-pyridyl)­acrylic acid) and (4-H₂pya)₄[M­(H₂O)₆]­[Co₂Mo₁₀H₄O₃₈]·5H₂O (M = Co <b>2</b>, Ni <b>3</b>, Cu <b>4</b>, Zn <b>5</b>, Cd <b>6</b>), were synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, solid diffuse reflective spectrum, powder X-ray diffraction, and single crystal X-ray diffraction. Compound <b>1</b> crystallizes in the centrosymmetric space group <i>P</i>-1, which is built up of protonated 4-H₂pya molecules and isolated [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanions. Isostructural compounds <b>2</b>–<b>6</b> crystallize in the chiral space group <i>P</i>1 by spontaneous resolution, as a conglomerate of two enantiomerically pure crystals, which were obtained by adding different metal cations to the reaction system of compound <b>1</b>. The structures of <b>2</b>–<b>6</b> comprise chiral [Co₂Mo₁₀H₄O₃₈]^6– anions, cationic [M­(H₂O)₆]²⁺ units, and protonated 4-H₂pya ligands. The chiral [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanions can be connected up together by directional hydrogen-bonding interactions among terminal oxygen atoms of anions, coordinated water molecules and organic ligands to construct a 3D supramolecular chiral framework in <b>2</b>–<b>6</b>. The absolute configuration of <b>2</b>–<b>6</b> was determined from the Flack parameter by X-ray crystallography and solid state circular dichroism spectroscopy. As far as we know, compounds <b>2</b>–<b>6</b> represent the first examples of chiral inroganic-organic hybrid species based on Evans–Showell-type polyoxometalates. Furthermore, the second harmonic generation (SHG) activities for <b>2</b> and <b>4</b> were measured, showing an SHG efficiency of approximately 0.9 × KH₂PO₄

Remarkable Stereochemistry Control in the Polymerization of α‑Olefins Using a Simple Scandium Catalyst System

A convenient approach to highly isotactic poly­(α-olefin)­s (<i>mmmm</i> > 99%) was realized using a simple scandium-based catalyst system consisting of ScCl₃(THF)₃, Al^<i>i</i>Bu₃, and [Ph₃C]­[B­(C₆F₅)₄] under mild conditions. The resultant polymers possess ultrahigh molecular weight (<i>M</i>_n > 10⁶) and relatively narrow molecular weight distribution. Especially, the excellent stereoselectivity still remains even at an elevated reaction temperature of 80 °C. Aluminum alkyls and organic borates, as well as their loadings significantly affected both the catalyst activity and product stereochemistry. The initial mechanistic exploration was carried out by means of NMR and ICP–AES spectroscopy, suggesting that a kind of incompact ion pair might be the active species. Further efforts to elucidate the real active sites and stereochemistry control mechanism of the catalytic system are underway

Spontaneous Resolution of Evans–Showell-Type Polyoxometalates in Constructing Chiral Inorganic–Organic Hybrid Architectures

Six new hybrid compounds based on [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanion, (4-H₂pya)₆Co₂Mo₁₀H₄O₃₈·10H₂O <b>1</b> (4-Hpya =3-(4-pyridyl)­acrylic acid) and (4-H₂pya)₄[M­(H₂O)₆]­[Co₂Mo₁₀H₄O₃₈]·5H₂O (M = Co <b>2</b>, Ni <b>3</b>, Cu <b>4</b>, Zn <b>5</b>, Cd <b>6</b>), were synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, solid diffuse reflective spectrum, powder X-ray diffraction, and single crystal X-ray diffraction. Compound <b>1</b> crystallizes in the centrosymmetric space group <i>P</i>-1, which is built up of protonated 4-H₂pya molecules and isolated [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanions. Isostructural compounds <b>2</b>–<b>6</b> crystallize in the chiral space group <i>P</i>1 by spontaneous resolution, as a conglomerate of two enantiomerically pure crystals, which were obtained by adding different metal cations to the reaction system of compound <b>1</b>. The structures of <b>2</b>–<b>6</b> comprise chiral [Co₂Mo₁₀H₄O₃₈]^6– anions, cationic [M­(H₂O)₆]²⁺ units, and protonated 4-H₂pya ligands. The chiral [Co₂Mo₁₀H₄O₃₈]^6– polyoxoanions can be connected up together by directional hydrogen-bonding interactions among terminal oxygen atoms of anions, coordinated water molecules and organic ligands to construct a 3D supramolecular chiral framework in <b>2</b>–<b>6</b>. The absolute configuration of <b>2</b>–<b>6</b> was determined from the Flack parameter by X-ray crystallography and solid state circular dichroism spectroscopy. As far as we know, compounds <b>2</b>–<b>6</b> represent the first examples of chiral inroganic-organic hybrid species based on Evans–Showell-type polyoxometalates. Furthermore, the second harmonic generation (SHG) activities for <b>2</b> and <b>4</b> were measured, showing an SHG efficiency of approximately 0.9 × KH₂PO₄

Bis(oxazolinyl)phenyl-Ligated Rare-Earth-Metal Complexes: Highly Regioselective Catalysts for <i>cis</i>-1,4-Polymerization of Isoprene

NCN-pincer (<i>S,S</i>)-2,6-bis­(4′-isopropyl-2′-oxazolinyl)­phenyl-ligated rare-earth-metal dichlorides [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]­LnCl₂(THF)₂ (Ln = Sc (<b>1</b>); Y (<b>2</b>); Dy (<b>3</b>); Ho (<b>4</b>); Tm (<b>5</b>); Lu (<b>6</b>)) were synthesized via transmetalation between [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]Li and LnCl₃ in THF solvent. Interestingly, treatment of LaCl₃ by the same method generated tris­(ligand) lanthanum complex [(<i>S,S</i>)-Phebox-^<i>i</i>Pr]₃La (<b>7</b>). Molecular structures of complexes <b>1</b>, <b>2</b>, <b>3</b>, and <b>7</b> were established by single-crystal X-ray diffraction study. Pincer ligand (<i>S,S</i>)-Phebox-^<i>i</i>Pr adopts a κC:κN:κN′ tridentate coordination mode to the central metal ion. Upon activation with [PhNHMe₂]­[B­(C₆F₅)₄] and Al^<i>i</i>Bu₃, complexes <b>2</b>–<b>5</b> exhibited highly catalytic activities and more than 98% <i>cis</i>-1,4-selectivity for isoprene polymerization while complexes <b>1</b> and <b>6</b> were inactive for this reaction. When use of the catalyst system consisted of complex <b>2</b>, [PhNHMe₂]­[B­(C₆F₅)₄], and Al^<i>i</i>Bu₃ for isoprene polymerization, the resultant polymer has a high <i>cis</i>-1,4-selectivity up to 99.5%. The reaction temperature had little effect on the regioselectivity, and high <i>cis</i>-1,4-selectivity almost remained even at 80 °C

Remarkable Stereochemistry Control in the Polymerization of α‑Olefins Using a Simple Scandium Catalyst System

A convenient approach to highly isotactic poly­(α-olefin)­s (<i>mmmm</i> > 99%) was realized using a simple scandium-based catalyst system consisting of ScCl₃(THF)₃, Al^<i>i</i>Bu₃, and [Ph₃C]­[B­(C₆F₅)₄] under mild conditions. The resultant polymers possess ultrahigh molecular weight (<i>M</i>_n > 10⁶) and relatively narrow molecular weight distribution. Especially, the excellent stereoselectivity still remains even at an elevated reaction temperature of 80 °C. Aluminum alkyls and organic borates, as well as their loadings significantly affected both the catalyst activity and product stereochemistry. The initial mechanistic exploration was carried out by means of NMR and ICP–AES spectroscopy, suggesting that a kind of incompact ion pair might be the active species. Further efforts to elucidate the real active sites and stereochemistry control mechanism of the catalytic system are underway