Institute of Low Carbon economics

Suzhou, China

Institute of Low Carbon economics

Suzhou, China
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Nie K.,Soochow University of China | Fang L.,Soochow University of China | Yao Y.,Soochow University of China | Yao Y.,Institute of Low Carbon economics | And 3 more authors.
Inorganic Chemistry | Year: 2012

A series of neutral lanthanide alkoxides supported by an amine-bridged bis(phenolate) ligand were synthesized, and their catalytic behaviors for the polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were explored. The reactions of (C5H5)3Ln(THF) with amine-bridged bis(phenol) LH2 [L = Me2NCH 2CH2N{CH2-(2-OC6H2Bu t 2-3,5)}2] in a 1:1 molar ratio in THF for 1 h and then with 1 equiv each of 2,2,2-trifluoroethanol, benzyl alcohol, and 2-propanol gave the neutral lanthanide alkoxides LLn(OCH2CF 3)(THF) [Ln = Y (1), Yb (2), Er (3), Sm (4)], LY(OCH 2Ph)(THF) (5), and LY(OPri)(THF) (6), respectively. These lanthanide alkoxides are sensitive to moisture, and the yttrium complex [(LY)2(μ-OPri)(μ-OH)] (7) was also isolated as a byproduct during the synthesis of complex 6. Complexes 1-6 were well characterized by elemental analyses and IR and NMR spectroscopy in the cases of complexes 1 and 4-6. The definitive molecular structures of all of these complexes were determined by single-crystal X-ray analysis. It was found that complexes 1-6 can initiate efficiently the ring-opening polymerization of rac-LA and rac-BBL in a controlled manner. For rac-LA, polymerization gave polymers with very narrow molecular weight distributions (PDI ≤ 1.12) and very high heterotacticity (Pr up to 0.99). The observed activity-increasing order is in agreement with the order of the ionic radii, whereas the order for stereoselectivity is in the reverse order. For rac-BBL polymerization, the resultant polymers have narrow molecular distributions (PDI ≤ 1.26) and high syndiotacticity (Pr up to 0.83). It is worth noting that the activity-decreasing order Yb > Er > Y ≫ Sm is observed for rac-BBL polymerization, which is opposite to the order of ionic radii and to the order of activity for rac-LA polymerization. The ionic radii of lanthanide metals have no obvious effect on the stereoselectivity for rac-BBL polymerization, which is quite different from that for rac-LA polymerization. End-group analysis of the oligomer of rac-BBL suggested that elimination side reactions occurred slowly in these systems, which led to chain cleavage and the formation of crotonate (and carboxy) end groups. © 2012 American Chemical Society.


Li W.,Soochow University of China | Zhang Z.,Soochow University of China | Yao Y.,Soochow University of China | Yao Y.,Institute of Low Carbon economics | And 2 more authors.
Organometallics | Year: 2012

A series of bimetallic and monometallic lanthanide amides stabilized by a piperazidine-bridged bis(phenolato) ligand were successfully prepared, and the factors controlling the formation of these lanthanide amides were elucidated. Reactions of Ln[N(TMS) 2] 3(μ-Cl)Li(THF) 3 (TMS = SiMe 3; THF = tetrahydrofuran) with a piperazidine-bridged bis(phenol), H 2[ONNO][4-bis(2-hydroxy-3,5-di-tert-butylbenzyl) piperazidine], in a 2:1 molar ratio in THF at 60 °C gave the anionic bimetallic bis(phenolato) lanthanide amido complexes [ONNO]{Ln[N(TMS) 2] 2(μ-Cl)Li(THF)} 2 [Ln = Y (1), Er (2), Eu (3), Sm (4)], whereas the same reactions conducted at room temperature gave the monometallic bis(phenolato) lanthanide amides [ONNO]LnN(TMS) 2(THF) [Ln = Y (5), Sm (6)]. Complex 1 can be transformed to a neutral bimetallic bis(phenolato) yttrium amido complex, [ONNO]{Y[N(TMS) 2] 2} 2 (7), by heating a toluene solution to 80 °C. Complex 7 can also be conveniently prepared by the reaction of the yttrium amide Y[N(TMS) 2] 3 with H 2[ONNO] in a 2:1 molar ratio at 60 °C. For neodymium and praseodymium, only the monometallic lanthanide amido complexes [ONNO]LnN(TMS) 2(THF) [Ln = Nd (8), Pr (9)] were isolated, even when the reactions were conducted at 60 °C. Furthermore, reaction of H 2[ONNO] with the less bulky lanthanide amides Ln[N(SiMe 2H) 2] 3(THF) 2 in a 2:1 molar ratio at 60 °C gave the monometallic lanthanide amido complexes [ONNO]Ln[N(SiMe 2H) 2](THF) [Ln = Yb (10), Y(11), Nd (12)] as neat products; no bimetallic species were formed. All of these complexes were characterized by IR, elemental analyses, and single-crystal X-ray diffraction. Complexes 1, 5, 6, 7, and 11 were further confirmed by NMR spectroscopy. These complexes are highly efficient initiators for the ring-opening polymerization of l-lactide. In addition, complexes 1, 3, 5, 7, and 11 can initiate rac-lactide polymerization with high activity to give heterotactic-rich polylactides. © 2012 American Chemical Society.


Sun Q.,Soochow University of China | Wang Y.,Soochow University of China | Yuan D.,Soochow University of China | Yao Y.,Soochow University of China | And 2 more authors.
Organometallics | Year: 2014

Zirconium and titanium complexes 1 and 2, bearing an amine-bridged bis(phenolato) ligand, have been synthesized and characterized. Although 1 and 2 were inactive in catalyzing intermolecular hydroamination reactions, cationic complexes generated in situ from treatment of 1 and 2 with borate [Ph 3C][B(C6F5)4], respectively, were found to be highly active. In general, excellent yields (up to >99%) and 100% regioselectivity for a broad range of terminal alkynes and anilines were observed within a reaction time of 1 h. Reactions with internal alkynes of moderate sterics also led to good yields and moderate regioselectivity. A kinetic study was also conducted, which provided some insights into the mechanism of hydroamination reactions. © 2014 American Chemical Society.


Zhang J.,Soochow University of China | Qiu J.,Soochow University of China | Yao Y.,Soochow University of China | Yao Y.,Institute of Low Carbon economics | And 3 more authors.
Organometallics | Year: 2012

A series of neutral lanthanide complexes supported by aminophenoxy ligands were synthesized, and their catalytic behavior in the polymerization of l-lactide and rac-lactide was explored. The amine elimination reactions of equimolar amounts of Ln[N(TMS) 2] 3(ν-Cl)Li(THF) 3 and aminophenol [HONH] 1 {[HONH] 1 = 2,6-Me 2-C 6H 4NHCH 2(3,5- tBu 2-C 6H 2-2-OH)} in toluene gave the dimeric lanthanide complexes {[ON] 1Ln[ONH] 1} 2 (Ln = La (1), Nd (2)), whereas the similar reactions of La[N(TMS) 2] 3(THF) 2 or Ln[N(TMS) 2] 3(ν-Cl)Li(THF) 3 (Ln = Nd, Sm) with the aminophenols [HONH] 2 {[HONH] 2 = (μ-OCH 3-C 6H 4)NHCH 2(3,5- tBu 2-C 6H 2-2-OH} and [HONH] 3 {[HONH] 3 = (NC 5H 4)NHCH 2(3,5- tBu 2-C 6H 2-2-OH)} generated the neutral aminophenoxy lanthanide amides {[ON] 2Ln[N(TMS) 2]} 2 [Ln = La (3), Nd (4), Sm (5)] and {[ON] 3Ln[N(TMS) 2](THF)} 2 [Ln = La (6), Nd (7), Sm (8)], respectively, in high isolated yields. These complexes have been fully characterized. X-ray structural determination revealed that complexes 1 and 2 have unsolvated centrosymmetric dimeric structures, in which one hydrogen atom belonging to the amino group of the ligand is reserved. Complexes 3-5 are isostructural and have an unsolvated dimeric structure. The coordination geometry around each of the lanthanide metal atoms can be described as a distorted trigonal bipyramid. Complexes 6 and 7 have a solvated dimeric structure, and the lanthanide metal centers have distorted capped trigonal-prismatic geometries. It was found that complexes 3-8 are highly efficient initiators for the ring-opening polymerization of l-lactide and rac-lactide, affording polymers with high molecular weights. © 2012 American Chemical Society.


Sun S.,Soochow University of China | Nie K.,Soochow University of China | Tan Y.,Soochow University of China | Zhao B.,Soochow University of China | And 4 more authors.
Dalton Transactions | Year: 2013

A series of neutral bimetallic lanthanide amido complexes supported by rigid phenylene bridged bis(β-diketiminate) ligands were synthesized, and their catalytic behavior for the polymerization of l-lactide and rac-lactide was explored. The amine elimination reaction of Ln[N(TMS)2] 3(μ-Cl)Li(THF)3 with PARA-H2, [PARA-H 2 = 2[2,6-iPr2C6H 3NHC(Me)C(H)C(Me)N]-(para-phenylene)] in a 2:1 molar ratio in THF at 25°C afforded the corresponding bimetallic lanthanide amido complexes PARA-{Ln[N(SiMe3)2]2}2 [Ln = Nd(1), Sm(2), Y(3)] in high isolated yields. Similar reaction of Nd[N(TMS) 2]3(μ-Cl)Li(THF)3 with META-H2, [META-H2 = 2[2,6-iPr2C6H 3NHC(Me)C(H)C(Me)N]-(meta-phenylene)] at 90°C in toluene for about 48 h gave META-{Nd[N(SiMe3)2]2} 2 (4). Complexes 1-4 were well characterized by elemental analysis, IR spectroscopy, and their definitive structures were confirmed by an X-ray crystal structure analysis. The coordination environment and coordination geometry around the metal atoms are similar in these complexes. Each of the metal atoms is four-coordinated with two nitrogen atoms from the N,N-chelating β-diketiminate unit, and two nitrogen atoms from two (Me 3Si)2N- groups to form a distorted tetrahedron. These complexes can serve as highly active initiators for l-lactide polymerization in toluene. In addition, they also showed high activity towards rac-lactide polymerization in THF at room temperature, giving heterotactic-enriched polymers (Pr ≈ 0.70), and complex 4 displays obviously higher activity in comparison with complex 1. © 2013 The Royal Society of Chemistry.


Qiu J.,Soochow University of China | Lu M.,Soochow University of China | Yao Y.,Soochow University of China | Yao Y.,Institute of Low Carbon economics | And 3 more authors.
Dalton Transactions | Year: 2013

Electronic properties of the aminophenolate groups have obvious effect on the synthesis of aminophenolate lanthanide-lithium complexes. Amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF) 3 with lithium aminophenolates [ArNHCH2(3,5- tBu2C6H2-2-O)Li(THF)]2 (Ar = p-ClC6H4, [ONH]Cl-p; p-BrC 6H4, [ONH]Br-p) in tetrahydrofuran (THF) in a 1:2 molar ratio gave the bimetallic lanthanide-lithium amido complexes [NO] Cl-p 2Ln[N(SiMe3)2][Li(THF)] 2 (Ln = Y (1), Yb (2)), and [NO]Br-p 2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (3), Yb (4)). When the Ar groups are p-MeOC6H4, ([ONH]MeO-p) and o-MeOC6H4 ([ONH] MeO-o), similar reactions generated the homoleptic lanthanide-lithium complexes [NO]MeO-p 3Ln[Li(THF)]3 (Ln = Y (5), Yb (6)) and [NO]MeO-o 2Ln[Li(THF)] (Ln = Y (7), Yb (8)) in high isolated yields, respectively. Whereas the bimetallic lanthanide-lithium amido complexes [NO]Cl-o 2Ln[N(SiMe3) 2][Li(THF)]2 (Ln = Y (9), Yb (10)) can be obtained in good yields, when the Ar group is o-ClC6H4 ([ONH] Cl-o). All of these complexes were well characterized. X-ray structure determination revealed that these complexes have solvated monomeric structures. In complexes 1-4, 9, and 10, the lanthanide atom is five-coordinated by two oxygen atoms and two nitrogen atoms from two aminophenoxy ligands and one nitrogen atom from N(SiMe3)2 group to form a distorted trigonal bipyramidal geometry, whereas in complexes 5-8, the central lanthanide atom is six-coordinated by oxygen atoms, and nitrogen atoms from the aminophenoxy ligands to form a distorted octahedron. It was found that complexes 1-10 are highly efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC), affording the polymers with high molecular weights, and the homoleptic heterobimetallic lanthanide complexes showed apparently high activity. © 2013 The Royal Society of Chemistry.


Nie K.,Soochow University of China | Gu W.,Soochow University of China | Yao Y.,Soochow University of China | Yao Y.,Institute of Low Carbon economics | And 2 more authors.
Organometallics | Year: 2013

A series of neutral lanthanide complexes supported by ONNO Salalen-type ligands were synthesized, and their catalytic activity for the polymerization of rac-lactide (rac-LA) was explored. The amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with the ONNO Salalen-type ligand L1H2 (L1 = (2-O-C6H2-But 2-3,5)CH-NCH 2CH2N(Me)CH2(2-O-C6H 2-But 2-3,5)) in a 1:1 molar ratio in tetrahydrofuran (THF) gave the neutral lanthanide amides L 1Ln[N(SiMe3)2](THF) (Ln = Y (1), Sm (2), Nd (3)). Reaction of the lanthanide amides with benzyl alcohol produces the dimeric lanthanide alkoxo complex (L1LnOCH2Ph)2 (Ln = Y (4), Sm (5)) in high isolated yield. Y[N(SiMe3)2] 3(μ-Cl)Li(THF)3 reacted with the Salalen-type ligand L2H2 (L2 = (2-O-C6H 2-But 2-3,5)CH-NCH2CH 2N(Me)CH2{2-O-C6H2-(CPhMe 2)2-3,5}) in a 1:l molar ratio in THF also gave the desired yttrium amide, but this complex could not be separated because of its very good solubility even in n-pentane. The proton exchange reactions of L 1H2 and L2H2 with (C 5H5)3Ln(THF) in a 1:1 molar ratio in THF and then with 1 equiv of benzyl alcohol gave the desired lanthanide alkoxides [L1Ln(OCH2Ph)]2 (Ln = Y (4), Sm (5), Yb (6)) and [L2Y(OCH2Ph)]2 (7), respectively. Complexes 1-7 were well characterized by elemental analyses, IR spectra, X-ray single-crystal structure determination, and NMR spectroscopy in the case of complexes 1, 4, and 7. Complexes 1-3 are isostructural and have a solvated monomeric structure. The coordination geometry around the lanthanide atom can be best described as a distorted trigonal bipyramid. Complexes 4-7 are dimeric species in the solid state. They all contain a Ln2O2 core bridging through the oxygen atoms of the two OCH2Ph groups. Each of the lanthanide atoms is also six-coordinated to form a distorted octahedron. It was found that all the complexes are efficient initiators for the ring-opening polymerization of rac-LA, giving PLA with good heterotacticity (Pr up to 0.85). The observed order of increase in activity is in agreement with the order of the ionic radii, whereas the stereoselectivity is in reverse order. The steric bulkiness of the substituents on the phenol ring has no obvious impact on the rate and stereocontrolability of the polymerizations. The Ln-O species resulted in more controllable polymerization than the corresponding Ln-N species, and complex 4 can initiate rac-LA polymerization in a controlled manner. © 2013 American Chemical Society.


Li W.,Soochow University of China | Wu W.,Soochow University of China | Wang Y.,Soochow University of China | Yao Y.,Soochow University of China | And 3 more authors.
Dalton Transactions | Year: 2011

Two dinuclear aluminum alkyl complexes supported by a piperazidine-bridged bis(phenolato) group were prepared, and both complexes exhibited extremely high activity for the ring-opening polymerization of ε-caprolactone. In the presence of benzyl alcohol (BnOH), the polymerization accelerated dramatically. © 2011 The Royal Society of Chemistry.


Qin J.,Soochow University of China | Wang P.,Soochow University of China | Li Q.,Soochow University of China | Zhang Y.,Soochow University of China | And 3 more authors.
Chemical Communications | Year: 2014

Readily available lanthanide complexes stabilized by a bridged poly(phenolate) ligand have been used for the first time as efficient catalysts for the insertion of CO2 into epoxides to generate cyclic carbonates with high activity, high selectivity, and a wide substrate scope under mild conditions. This journal is © the Partner Organisations 2014.


Sun S.,Soochow University of China | Sun Q.,Soochow University of China | Zhao B.,Soochow University of China | Zhang Y.,Soochow University of China | And 3 more authors.
Organometallics | Year: 2013

Treatment of META-[Na(THF)2]2 (1; META = {[2,6- iPr2C6H3NC(Me)C(H)C(Me)N] -}2-(m-phenylene)] with 1 equiv of {Ln[N(SiMe 3)2]2(μ-Cl)(THF)}2 (Ln = Y, Yb) in toluene at 110 C afforded bimetallic lanthanide amido complexes bridged by a chloride and a phenyl group, {Ln[N(SiMe3)2]} 2(META′)(μ-Cl) (Ln = Y (2), Yb (3)), which formed via unexpected C-H bond activation of the arene ring. However, the same reactions carried out in both THF and toluene at room temperature gave the bimetallic lanthanide amido-chloro complexes {Ln[N(SiMe3)2] 2}META{Ln[N(SiMe3)2]Cl(THF)} (Ln = Y (4), Yb (5)). When they were heated to 110 C in toluene, complexes 4 and 5 were converted to complexes 2 and 3 via amine elimination. All of these complexes were confirmed by elemental analysis, FT-IR, and X-ray structure analysis and by NMR analysis in the cases of complexes 1, 2, and 4. © 2013 American Chemical Society.

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