The Experts below are selected from a list of 9054 Experts worldwide ranked by ideXlab platform
Qi Shen - One of the best experts on this subject based on the ideXlab platform.
-
synthesis and characterization of ytterbium guanidinates stabilized by bridged bis Phenolate ligand and their application for the hydrophosphonylation reaction of aldehydes
Journal of Organometallic Chemistry, 2015Co-Authors: Tinghua Zeng, Yingming Yao, Qinqin Qian, Yaorong Wang, Qi ShenAbstract:Abstract A series of ytterbium guanidinato complexes stabilized by an amine-bridged bis(Phenolate) ligand were prepared, and their catalytic property for the hydrophosphonylation reaction of aldehydes was explored. Metathesis reactions of amine-bridged bis(Phenolate) ytterbium chlorides LYbCl(THF) [L = Me 2 NCH 2 CH 2 N{CH 2 -(2-OC 6 H 2 t Bu 2 -3,5)} 2 ] with corresponding lithium guanidinates in a 1:1 molar ratio in THF gave the expected ytterbium guanidinato complexes LYb[R 2 NC(NR 1 ) 2 ] [R 1 = Cy, R 2 N = N(TMS) 2 ( 1 ), N(CH 2 ) 5 ( 2 ); R 1 = i Pr, R 2 N = N(TMS) 2 ( 3 ), NPh 2 ( 4 )]. These ytterbium complexes were well characterized by elemental analyses, IR spectroscopy and single-crystal X-ray structure determination. The metal ion is six-coordinated by two oxygen and two nitrogen atoms from the bis(Phenolate) ligand, and two nitrogen atoms from one guanidinato group. The coordination geometry around ytterbium can be described as a distorted octahedron. It was found that these ytterbium guanidinato complexes are highly efficient catalysts for the hydrophosphonylation reaction of various aldehydes under mild conditions.
-
highly heteroselective ring opening polymerization of racemic lactide initiated by divalent ytterbium complexes bearing amino bis Phenolate ligands
Chemical Communications, 2012Co-Authors: Sheng Yang, Yong Zhang, Qi ShenAbstract:Polymerization of racemic lactide initiated by divalent ytterbium complexes supported by either dimethylamino-amino bis(Phenolate) or methoxy-amino bis(Phenolate) ligands proceeds rapidly at room temperature in a living fashion to give heterotactic polylactide with the racemic enchainment of monomer units Pr ranging from 0.97–0.99.
-
controlled syntheses characterization and reactivity of neutral and anionic lanthanide amides supported by methylene linked bis Phenolate ligands
Inorganic Chemistry, 2007Co-Authors: Zhongjian Zhang, Yingming Yao, Yong Zhang, Qi ShenAbstract:A series of neutral and anionic bis(Phenolate) lanthanide amides were synthesized by general metathesis reactions, and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH 2 (MBMP = 2,2'-methylene bis-(6-tert-butyl-4-methyl-Phenolate)) with [Ln{N(TMS) 2 } 2 (μ-Cl)(THF)]2 (TMS = SiMe 3 ) afforded the desired bridged bis(Phenolate) lanthanide chlorides [(MBMP)Ln(μ-CI)(THF) 2 ] 2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives. Reactions of 1 and 2 with 2 equiv of NaN(TMS) 2 in THF produced the expected neutral bis(Phenolate) lanthanide amido complexes (MBMP)Ln[N(TMS)2](THF)2 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 with LiN(TMS) 2 in a 1:4 molar ratio gave the anionic bis(Phenolate) lanthanide amides as discrete ion-pair complexes [Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH 2 with [Ln{N(TMS) 2 } 2 (μ-Cl)(THF)] 2 in a 2:1 molar ratio, and then with 4 equiv of n BuLi. The reactivity of the neutral and anionic bis-(Phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(Phenolate) lanthanide guanidinate complexes [(μ-Ο-MBMP)Nd{( j PrN)2CN(TMS)2}]2 (7) and (MBMP)Yb[('PrN)2CN(TMS)2] (8), respectively, in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpected ligand-redistributed products, and the homoleptic ion-pair bis(Phenolate) neodymium complex [Li(DME) 2 (THF)]-[(MBMP) 2 Nd(THF) 2 ] (9) was finally isolated as one of the products. Furthermore, the anionic bis(Phenolate) lanthanide amides showed higher catalytic activity for the polymerization of e-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.
-
synthesis reactivity and characterization of amine bis Phenolate lanthanide complexes and their application in the polymerization of e caprolactone
Organometallics, 2005Co-Authors: Yingming Yao, Yong Zhang, Qi Shen, Wing Tak WongAbstract:A series of amine bis(phenolato)lanthanide methyl and amido complexes were synthesized by general salt metathesis reaction in this paper. The reaction of anhydrous lanthanide trichlorides with 1 equiv of sodium amine bis(Phenolate) LNa2 [L = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in THF at room temperature gave the amine bis(Phenolate) lanthanide chlorides LLnCl(THF) (Ln = Yb (1), Ln = Er (2)). Complexes 1 and 2 can be used as starting materials to prepare amine bis(Phenolate) lanthanide derivatives. Complexes 1 and 2 reacted with lithium methyl and lithium amide, respectively, to give the corresponding lanthanide methyl and amido products LLnMe(THF) (Ln = Yb (3), Ln = Er (4)) and LLnNPh2(THF) (Ln = Yb (5), Ln = Er (6)). These complexes were well characterized by elemental analyses and IR spectra. The definitive molecular structures of complexes 1, 2, 3, 5, and 6 were provided by single-crystal X-ray analyses. Reactivity studies of complexes 3, 5, and 6 have shown them to be efficient initiators for the r...
Vanderlei G Machado - One of the best experts on this subject based on the ideXlab platform.
-
solvatochromic behavior of substituted 4 nitrostyryl Phenolate dyes in pure solvents and in binary solvent mixtures composed of water and alcohols
Journal of Molecular Liquids, 2018Co-Authors: Rafaela I. Stock, Crislaine Sandri, Marcos Caroli Rezende, Vanderlei G MachadoAbstract:Abstract Several 4-(nitrostyryl)Phenolates have been used recently as solvatochromic dyes in the investigation of pure solvents. Changes in their molecular structures allow a comparison of their solvation patterns to be made in different binary solvent mixtures, in an effort to relate structural factors to the preferential solvation (PS) observed in these media. Firstly, the solvatochromism of four of these probes was studied and a reversal in their solvatochromism was verified, which was expected following a comparison with other similar systems previously studied. The solvatochromic behavior of a series of twelve 4-(nitrostyryl)Phenolate dyes was then investigated in water-alcohol mixtures. A sigmoid behavior was verified for one of the dyes in ethane-1,2-diol-water mixtures, and the dye was preferentially solvated by water in the alcohol-rich region. For all other mixture compositions a strong synergy was observed, with the PS of the dye molecules occurring through the less polar moiety of the water-alcohol aggregates in the binary mixtures. In addition, synergy was observed for some dyes, with PS occurring through the less polar moiety of the alcohol-water aggregates. For all of the other water-alcohol mixtures, the probes were preferentially solvated by the alcohol cosolvent. In order to quantify these deviations, a PS (or non-ideality) index PSI was proposed. The PSI values obtained correlated well with the hydrogen-bond donating ability of the alcoholic co-solvent, and also with the basicity of the Phenolate dyes, and the trends observed were confirmed with data from the literature for two other Phenolate dyes.
-
nitro substituted 4 phenylmethylene imino Phenolates solvatochromism and their use as solvatochromic switches and as probes for the investigation of preferential solvation in solvent mixtures
Journal of Organic Chemistry, 2012Co-Authors: Leandro G. Nandi, Giovanni F. Caramori, Felipe Facin, Vanderleia Gava Marini, Lizandra M Zimmermann, Luciano Albino Giusti, Robson Da Silva, Vanderlei G MachadoAbstract:Four 4-[[(4-nitrophenyl)methylene]imino]phenols (2a–d) were synthesized. After deprotonation in solution, they formed the solvatochromic Phenolates 3a–d, which revealed a reversal in solvatochromism. Their UV–vis spectroscopic behavior was explained on the basis of the interaction of the dyes with the medium through combined effects, such as nonspecific solute–solvent interactions and hydrogen bonding between the solvents and the nitro and Phenolate groups. Dyes 3a–c were used as probes to investigate binary solvent mixtures, and the synergistic behavior observed was attributed to solvent–solvent and solute–solvent interactions. A very unusual UV–vis spectroscopic behavior occurred with dye 3d, which has in its molecular structure two nitro substituents as acceptor groups and two phenyl groups on the Phenolate moiety. In alcohol/water mixtures, the ET(3d) values increase from pure alcohol (methanol, ethanol, and propan-2-ol) until the addition of up to 80–96% water. Subsequently, the addition of a small a...
Rafaela I. Stock - One of the best experts on this subject based on the ideXlab platform.
-
solvatochromic behavior of substituted 4 nitrostyryl Phenolate dyes in pure solvents and in binary solvent mixtures composed of water and alcohols
Journal of Molecular Liquids, 2018Co-Authors: Rafaela I. Stock, Crislaine Sandri, Marcos Caroli Rezende, Vanderlei G MachadoAbstract:Abstract Several 4-(nitrostyryl)Phenolates have been used recently as solvatochromic dyes in the investigation of pure solvents. Changes in their molecular structures allow a comparison of their solvation patterns to be made in different binary solvent mixtures, in an effort to relate structural factors to the preferential solvation (PS) observed in these media. Firstly, the solvatochromism of four of these probes was studied and a reversal in their solvatochromism was verified, which was expected following a comparison with other similar systems previously studied. The solvatochromic behavior of a series of twelve 4-(nitrostyryl)Phenolate dyes was then investigated in water-alcohol mixtures. A sigmoid behavior was verified for one of the dyes in ethane-1,2-diol-water mixtures, and the dye was preferentially solvated by water in the alcohol-rich region. For all other mixture compositions a strong synergy was observed, with the PS of the dye molecules occurring through the less polar moiety of the water-alcohol aggregates in the binary mixtures. In addition, synergy was observed for some dyes, with PS occurring through the less polar moiety of the alcohol-water aggregates. For all of the other water-alcohol mixtures, the probes were preferentially solvated by the alcohol cosolvent. In order to quantify these deviations, a PS (or non-ideality) index PSI was proposed. The PSI values obtained correlated well with the hydrogen-bond donating ability of the alcoholic co-solvent, and also with the basicity of the Phenolate dyes, and the trends observed were confirmed with data from the literature for two other Phenolate dyes.
-
synthesis and solvatochromism of substituted 4 nitrostyryl Phenolate dyes
Journal of Organic Chemistry, 2015Co-Authors: Rafaela I. Stock, Adriana D. S. Schramm, Celso R. Nicoleti, Leandro G. Nandi, Sheila L Meller, Renata S Heying, Daniel F Coimbra, Karla F Andriani, Giovanni F. Caramori, Adailton J BortoluzziAbstract:4-(Nitrostyryl)phenols 2a–9a were synthesized, and by deprotonation in solution, the solvatochromic Phenolates 2b–9b were formed. Their absorption bands in the vis region of the spectra are due to π–π* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor Phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO–LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C═C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, whic...
Adailton J Bortoluzzi - One of the best experts on this subject based on the ideXlab platform.
-
synthesis and solvatochromism of substituted 4 nitrostyryl Phenolate dyes
Journal of Organic Chemistry, 2015Co-Authors: Rafaela I. Stock, Adriana D. S. Schramm, Celso R. Nicoleti, Leandro G. Nandi, Sheila L Meller, Renata S Heying, Daniel F Coimbra, Karla F Andriani, Giovanni F. Caramori, Adailton J BortoluzziAbstract:4-(Nitrostyryl)phenols 2a–9a were synthesized, and by deprotonation in solution, the solvatochromic Phenolates 2b–9b were formed. Their absorption bands in the vis region of the spectra are due to π–π* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor Phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO–LUMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C═C bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, whic...
Yong Zhang - One of the best experts on this subject based on the ideXlab platform.
-
highly heteroselective ring opening polymerization of racemic lactide initiated by divalent ytterbium complexes bearing amino bis Phenolate ligands
Chemical Communications, 2012Co-Authors: Sheng Yang, Yong Zhang, Qi ShenAbstract:Polymerization of racemic lactide initiated by divalent ytterbium complexes supported by either dimethylamino-amino bis(Phenolate) or methoxy-amino bis(Phenolate) ligands proceeds rapidly at room temperature in a living fashion to give heterotactic polylactide with the racemic enchainment of monomer units Pr ranging from 0.97–0.99.
-
controlled syntheses characterization and reactivity of neutral and anionic lanthanide amides supported by methylene linked bis Phenolate ligands
Inorganic Chemistry, 2007Co-Authors: Zhongjian Zhang, Yingming Yao, Yong Zhang, Qi ShenAbstract:A series of neutral and anionic bis(Phenolate) lanthanide amides were synthesized by general metathesis reactions, and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH 2 (MBMP = 2,2'-methylene bis-(6-tert-butyl-4-methyl-Phenolate)) with [Ln{N(TMS) 2 } 2 (μ-Cl)(THF)]2 (TMS = SiMe 3 ) afforded the desired bridged bis(Phenolate) lanthanide chlorides [(MBMP)Ln(μ-CI)(THF) 2 ] 2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives. Reactions of 1 and 2 with 2 equiv of NaN(TMS) 2 in THF produced the expected neutral bis(Phenolate) lanthanide amido complexes (MBMP)Ln[N(TMS)2](THF)2 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 with LiN(TMS) 2 in a 1:4 molar ratio gave the anionic bis(Phenolate) lanthanide amides as discrete ion-pair complexes [Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH 2 with [Ln{N(TMS) 2 } 2 (μ-Cl)(THF)] 2 in a 2:1 molar ratio, and then with 4 equiv of n BuLi. The reactivity of the neutral and anionic bis-(Phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(Phenolate) lanthanide guanidinate complexes [(μ-Ο-MBMP)Nd{( j PrN)2CN(TMS)2}]2 (7) and (MBMP)Yb[('PrN)2CN(TMS)2] (8), respectively, in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpected ligand-redistributed products, and the homoleptic ion-pair bis(Phenolate) neodymium complex [Li(DME) 2 (THF)]-[(MBMP) 2 Nd(THF) 2 ] (9) was finally isolated as one of the products. Furthermore, the anionic bis(Phenolate) lanthanide amides showed higher catalytic activity for the polymerization of e-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.
-
synthesis reactivity and characterization of amine bis Phenolate lanthanide complexes and their application in the polymerization of e caprolactone
Organometallics, 2005Co-Authors: Yingming Yao, Yong Zhang, Qi Shen, Wing Tak WongAbstract:A series of amine bis(phenolato)lanthanide methyl and amido complexes were synthesized by general salt metathesis reaction in this paper. The reaction of anhydrous lanthanide trichlorides with 1 equiv of sodium amine bis(Phenolate) LNa2 [L = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in THF at room temperature gave the amine bis(Phenolate) lanthanide chlorides LLnCl(THF) (Ln = Yb (1), Ln = Er (2)). Complexes 1 and 2 can be used as starting materials to prepare amine bis(Phenolate) lanthanide derivatives. Complexes 1 and 2 reacted with lithium methyl and lithium amide, respectively, to give the corresponding lanthanide methyl and amido products LLnMe(THF) (Ln = Yb (3), Ln = Er (4)) and LLnNPh2(THF) (Ln = Yb (5), Ln = Er (6)). These complexes were well characterized by elemental analyses and IR spectra. The definitive molecular structures of complexes 1, 2, 3, 5, and 6 were provided by single-crystal X-ray analyses. Reactivity studies of complexes 3, 5, and 6 have shown them to be efficient initiators for the r...
