Chen-Yu Li

Synthesis, characterization and reactivity of single-site aluminium amides bearing benzotriazole phenoxide ligands: catalysis for ring-opening polymerization of lactide and carbon dioxide/propylene oxide coupling.

New aluminium complexes containing bis-BTP ligands (BTP = N,O-bidentate benzotriazole phenoxide) were synthesized and structurally characterized. Amine elimination of Al(NMe2)3 with (R)BTP-H ligands ((CMe2Ph)BTP-H = 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, (t-Bu)BTP-H = 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol and (TMCl)BTP-H = 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol) (2.0 mol equiv.) in toluene or hexane afforded the penta-coordinated single-site amidoaluminium complexes [((R)BTP)2Al(NMe2)] (R = CMe2Ph for 1; R = t-Bu for 2; R = TMCl for 3) in satisfactory yields. With the addition of H2O (0.5 molar equiv.), the hydrolysis of Al amides 2 and 3 in a mixed solvent of THF/toluene at 25 °C produced oxo-bridged bimetallic aluminium complexes [{((R)BTP)2Al}2(μ-O)] (R = t-Bu for 4 and R = TMCl for 5) in ≥70% yield. According to single crystal X-ray diffraction studies, complex 2 shows a monomeric Al(iii) amide with bis((t-Bu)BTP) ligands and one -NMe2 group, whereas alumoxane 4 is a dinuclear species, in which the bonding mode of the Al-O-Al moiety from μ2-oxo assumes a linear type. Catalysis for ring-opening polymerization of lactide (LA) and CO2/propylene oxide (PO) coupling was systematically studied. Single-site Al amide 3 is an efficient initiator for LA polymerizations with a living character; the polymerization displays a first-order dependence on the concentration of l-LA. Bimetallic BTP-ligated alumoxane 5 is an active catalyst (TOF: 120 h(-1)) for the coupling of CO2 with PO in the presence of n-Bu4NBr to give propylene carbonate under mild conditions.

Bimetallic nickel and cobalt complexes as high-performance catalysts for copolymerization of carbon dioxide with cyclohexene oxide

New bimetallic nickel, cobalt and zinc complexes bearing a bis(benzotriazole iminophenolate) ligand and ancillary acetate groups were developed for CO2/epoxide copolymerization. Ni and Co complexes are active catalysts for the copolymerization of cyclohexene oxide (CHO) and CO2 without co-catalysts. Particularly, well-defined di-Ni 1 was found to effectively copolymerize CHO with CO2, giving copolymers with a high molecular weight and a high carbonate linkage content. This is the first example of a dinuclear nickel acetate complex that is efficient for CO2/CHO copolymerization as well as for the formation of highly alternative poly(cyclohexene carbonate) in a controllable manner.

Evaluation of structural transformation in 2D metal–organic frameworks based on a 4,4′-sulfonyldibenzoate linker: microwave-assisted solvothermal synthesis, characterization and applications

Six 2D metal–organic frameworks containing V-shaped 4,4′-sulfonyldibenzoate (SBA) linkers, [Zn3(SBA)2(OH)2]·EtOH (1 or CYCU-5·EtOH), [M3(OH)2(SBA)2(EtOH)(H2O)3]·3.5H2O (2–4, M = Mg, Ni, and Co), [Mn(SBA)(EtOH)] (5) and [Mn(SBA)(H2O)] (6), have been synthesized rapidly under microwave-assisted solvothermal conditions. The structural analysis revealed that all compounds display two-dimensional structures containing inorganic motifs with one-dimensional chains (1–5) or dimers of trigonal prisms (6) connected through SBA linkers and forming 2D neutral and porous channels. Compounds 1–4 were further characterized by elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) measurements and IR spectroscopy. The desolvated phases of compounds 1–2/3–4 have thermal stabilities up to about 400/350 °C. The desolvated frameworks of 1–4 above 200 °C have similar CYCU-5-like conformations and exhibit gas adsorption properties with N2, CO2 and H2 gases. Interestingly, CYCU-5 displays selective adsorption of CO2 over N2 and CH4 gases at 273 K. In addition, the catalytic ability of CYCU-5 as an initiator for ring-opening polymerization of L-lactide has also been demonstrated.

Bis{1-[(E)-(2-methyl-phen-yl)diazen-yl]-2-naphtho-lato}palladium(II).

In the title compound, [Pd(C17H13N2O)2], the PdII atom is tetracoordinated by two N atoms and two O atoms from two bidentate methylphenyldiazenylnaphtolate ligands, forming a square-planar complex. The two N atoms and two O atoms around the PdII atom are trans to each other (as the PdII atom lies on a crystallographic inversion centre) with O—Pd—N bond angles of 89.60 (11) and 90.40 (11)°. The distances between the PdII atom and the coordinated O and N atoms are 1.966 (3) and 2.009 (3) Å, respectively.

Bis{1-[(E)-o-tolyl­diazen­yl]-2-naphtho­l­ato}copper(II)

In the title complex, [Cu(C17H13N2O)2], the CuII atom is tetracoordinated by two N atoms and two O atoms from two bidentate 1-[(E)-o-tolyldiazenyl]-2-naphtholate ligands, forming a slightly distorted square-planar environment. The two N atoms and two O atoms around the CuII atom are trans to each other, with an O—Cu—O bond angle of 177.00 (9)° and an N—Cu—N bond angle of 165.63 (10)°. The average distances between the CuII atom and the coordinated O and N atoms are 1.905 (2) and 1.995 (2)Å, respectively.

Bis[μ-2-(2H-benzotriazol-2-yl)-4-methyl-phenolato]bis-[dimethyl-aluminium(III)].

The title complex, [Al2(CH3)4(C13H10N3O)2], is dimeric, bridged through the O atoms of the phenolate anions. The asymmetric unit contains one half of the molecule and there is a crystallographic inversion centre in this molecule. Each Al atom is pentacoordinated by one N atom and two bridging O atoms of two N,O-bidentate benzotriazolylphenolate ligands and by two C atoms from two methyl groups, forming a distorted trigonal–bipyramidal environment.

(E)-2-(2H-Benzotriazol-2-yl)-4-methyl-6-(phenyl-imino-meth-yl)phenol.

In the title compound, C20H16N4O, the non-H atoms of the benzotriazole ring system and those of the methylphenol group are essentially coplanar, with an r.m.s. deviation of 0.004 (2) Å. The mean plane of these atoms forms a dihedral angle of 60.9 (2)° with the phenyl ring. There is an intramolecular O—H⋯N hydrogen bond between the phenol and benzotriazole groups.

Bis[2-(2H-benzotriazol-2-yl)-4-methyl-6-(phenyl-imino-methyl-κN)phenolato-κO]palladium(II).

In the title complex, [Pd(C20H15N4O)2], the PdII atom is tetracoordinated by two N atoms and two O atoms from two bidentate imine–benzotriazole phenolate ligands, forming a square-planar environment. The asymmetric unit contains two half-molecules in both of which the PdII atom lies on a centre of symmetry. The average distances between the PdII atom and the coordinated O and N atoms are 1.9831 (12) and 2.012 (2) Å, respectively.

2-(2H-Benzotriazol-2-yl)-6-[(dicyclo­hexyl­amino)­meth­yl]-4-(2,4,4-trimethyl­pentan-2-yl)phenol

In the title molecule, C33H48N4O, the dihedral angle between the mean planes of the benzotriazole ring system [maximun deviation = 0.038 (2) Å] and the phenol ring is 16.6 (2)°. There is an intramolecular O—H⋯N hydrogen bond between the phenol and benzotriazole groups.

2-(2-Meth­oxy-5-methyl­phen­yl)-2H-benzotriazole

In the title molecule, C14H13N3O, the dihedral angle between the mean planes of the benzotriazole ring system and the benzene ring is 57.8 (2)°.