Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes

Jose A Castro-Osma; Carlos Alonso-Moreno; Isabel Márquez-Segovia; Antonio Otero; Agustín Lara-Sánchez; Juan Fernández-Baeza; Ana M Rodríguez; Luis F Sánchez-Barba; Joaquín C García-Martínez

doi:10.1039/c3dt32657h

Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes

Jose A Castro-Osma, Carlos Alonso-Moreno, Isabel Márquez-Segovia, Antonio Otero, Agustín Lara-Sánchez, Juan Fernández-Baeza, Ana M Rodríguez, Luis F Sánchez-Barba, Joaquín C García-Martínez

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

Five-coordinate alkyl aluminium complexes [AlR(κ(2)-pbpam)2] (R = Me 1, Et 2), [AlR(κ(2)-sbpam)2] (R = Me 3, Et 4) and [AlR{κ(2)-(S)-mbpam}2] (R = Me 5, Et 6), -pbpam [pbpam = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate], sbpam [sbpam = N-sec-butyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] and (S)-mbpam [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] were obtained by an alkane elimination route involving the reaction of the previously reported acetamide heteroscorpionate precursors with 0.5 equiv. of the corresponding AlR3. In the solid state, complexes 1-6 adopt a distorted trigonal bipyramidal structure with the heteroscorpionate ligands arranged in a κ(2)-NO coordination mode. The molecular structures of 1-6 in solution were studied by VT NMR spectroscopy and a fluxional exchange between coordinated and noncoordinated pyrazole rings was observed. This process led to interconversion between the different isomers. Compounds 4 and 6 were used as precursors for the synthesis of the aryloxide aluminium compounds [Al(OR)(κ(2)-sbpam)2] (7) and [Al(OR){κ(2)-(S)-mbpam}2] (8) (R = 2,6-Me2C6H3O) by reaction with the corresponding 2,6-dimethylphenol. The structures of the complexes were determined by spectroscopic methods, and the X-ray crystal structures of 2, 6 and 7 were also established. Five-coordinate compounds 1-8 were evaluated as initiators in the ring-opening polymerization of rac-lactide. Compound 5 was also evaluated in the presence of a co-initiator. Finally, a study of the block and random copolymerization of ε-caprolactone and L-lactide was carried out.

Original language	English
Pages (from-to)	9325-9337
Number of pages	13
Journal	Dalton Transactions
Volume	42
Issue number	25
Early online date	8 Feb 2013
DOIs	https://doi.org/10.1039/c3dt32657h
Publication status	Published - 7 Jul 2013

Keywords

Aluminum
Caproates
Catalysis
Dioxanes
Lactones
Models, Molecular
Molecular Structure
Organometallic Compounds
Polymerization

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10.1039/c3dt32657h

Cite this

Castro-Osma, J. A., Alonso-Moreno, C., Márquez-Segovia, I., Otero, A., Lara-Sánchez, A., Fernández-Baeza, J., Rodríguez, A. M., Sánchez-Barba, L. F., & García-Martínez, J. C. (2013). Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes. Dalton Transactions, 42(25), 9325-9337. https://doi.org/10.1039/c3dt32657h

@article{4f2ed992fd96472784516b8dde3af5ce,

title = "Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes",

abstract = "Five-coordinate alkyl aluminium complexes [AlR(κ(2)-pbpam)2] (R = Me 1, Et 2), [AlR(κ(2)-sbpam)2] (R = Me 3, Et 4) and [AlR{κ(2)-(S)-mbpam}2] (R = Me 5, Et 6), -pbpam [pbpam = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate], sbpam [sbpam = N-sec-butyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] and (S)-mbpam [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] were obtained by an alkane elimination route involving the reaction of the previously reported acetamide heteroscorpionate precursors with 0.5 equiv. of the corresponding AlR3. In the solid state, complexes 1-6 adopt a distorted trigonal bipyramidal structure with the heteroscorpionate ligands arranged in a κ(2)-NO coordination mode. The molecular structures of 1-6 in solution were studied by VT NMR spectroscopy and a fluxional exchange between coordinated and noncoordinated pyrazole rings was observed. This process led to interconversion between the different isomers. Compounds 4 and 6 were used as precursors for the synthesis of the aryloxide aluminium compounds [Al(OR)(κ(2)-sbpam)2] (7) and [Al(OR){κ(2)-(S)-mbpam}2] (8) (R = 2,6-Me2C6H3O) by reaction with the corresponding 2,6-dimethylphenol. The structures of the complexes were determined by spectroscopic methods, and the X-ray crystal structures of 2, 6 and 7 were also established. Five-coordinate compounds 1-8 were evaluated as initiators in the ring-opening polymerization of rac-lactide. Compound 5 was also evaluated in the presence of a co-initiator. Finally, a study of the block and random copolymerization of ε-caprolactone and L-lactide was carried out.",

keywords = "Aluminum, Caproates, Catalysis, Dioxanes, Lactones, Models, Molecular, Molecular Structure, Organometallic Compounds, Polymerization",

author = "Castro-Osma, {Jose A} and Carlos Alonso-Moreno and Isabel M{\'a}rquez-Segovia and Antonio Otero and Agust{\'i}n Lara-S{\'a}nchez and Juan Fern{\'a}ndez-Baeza and Rodr{\'i}guez, {Ana M} and S{\'a}nchez-Barba, {Luis F} and Garc{\'i}a-Mart{\'i}nez, {Joaqu{\'i}n C}",

year = "2013",

month = jul,

day = "7",

doi = "10.1039/c3dt32657h",

language = "English",

volume = "42",

pages = "9325--9337",

journal = "Dalton Transactions",

issn = "1477-9234",

publisher = "The Royal Society of Chemistry",

number = "25",

}

Castro-Osma, JA, Alonso-Moreno, C, Márquez-Segovia, I, Otero, A, Lara-Sánchez, A, Fernández-Baeza, J, Rodríguez, AM, Sánchez-Barba, LF & García-Martínez, JC 2013, 'Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes', Dalton Transactions, vol. 42, no. 25, pp. 9325-9337. https://doi.org/10.1039/c3dt32657h

TY - JOUR

T1 - Synthesis, structural characterization and catalytic evaluation of the ring-opening polymerization of discrete five-coordinate alkyl aluminium complexes

AU - Castro-Osma, Jose A

AU - Alonso-Moreno, Carlos

AU - Márquez-Segovia, Isabel

AU - Otero, Antonio

AU - Lara-Sánchez, Agustín

AU - Fernández-Baeza, Juan

AU - Rodríguez, Ana M

AU - Sánchez-Barba, Luis F

AU - García-Martínez, Joaquín C

PY - 2013/7/7

Y1 - 2013/7/7

N2 - Five-coordinate alkyl aluminium complexes [AlR(κ(2)-pbpam)2] (R = Me 1, Et 2), [AlR(κ(2)-sbpam)2] (R = Me 3, Et 4) and [AlR{κ(2)-(S)-mbpam}2] (R = Me 5, Et 6), -pbpam [pbpam = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate], sbpam [sbpam = N-sec-butyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] and (S)-mbpam [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] were obtained by an alkane elimination route involving the reaction of the previously reported acetamide heteroscorpionate precursors with 0.5 equiv. of the corresponding AlR3. In the solid state, complexes 1-6 adopt a distorted trigonal bipyramidal structure with the heteroscorpionate ligands arranged in a κ(2)-NO coordination mode. The molecular structures of 1-6 in solution were studied by VT NMR spectroscopy and a fluxional exchange between coordinated and noncoordinated pyrazole rings was observed. This process led to interconversion between the different isomers. Compounds 4 and 6 were used as precursors for the synthesis of the aryloxide aluminium compounds [Al(OR)(κ(2)-sbpam)2] (7) and [Al(OR){κ(2)-(S)-mbpam}2] (8) (R = 2,6-Me2C6H3O) by reaction with the corresponding 2,6-dimethylphenol. The structures of the complexes were determined by spectroscopic methods, and the X-ray crystal structures of 2, 6 and 7 were also established. Five-coordinate compounds 1-8 were evaluated as initiators in the ring-opening polymerization of rac-lactide. Compound 5 was also evaluated in the presence of a co-initiator. Finally, a study of the block and random copolymerization of ε-caprolactone and L-lactide was carried out.

AB - Five-coordinate alkyl aluminium complexes [AlR(κ(2)-pbpam)2] (R = Me 1, Et 2), [AlR(κ(2)-sbpam)2] (R = Me 3, Et 4) and [AlR{κ(2)-(S)-mbpam}2] (R = Me 5, Et 6), -pbpam [pbpam = N-phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate], sbpam [sbpam = N-sec-butyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] and (S)-mbpam [(S)-mbpam = (S)-(-)-N-α-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate] were obtained by an alkane elimination route involving the reaction of the previously reported acetamide heteroscorpionate precursors with 0.5 equiv. of the corresponding AlR3. In the solid state, complexes 1-6 adopt a distorted trigonal bipyramidal structure with the heteroscorpionate ligands arranged in a κ(2)-NO coordination mode. The molecular structures of 1-6 in solution were studied by VT NMR spectroscopy and a fluxional exchange between coordinated and noncoordinated pyrazole rings was observed. This process led to interconversion between the different isomers. Compounds 4 and 6 were used as precursors for the synthesis of the aryloxide aluminium compounds [Al(OR)(κ(2)-sbpam)2] (7) and [Al(OR){κ(2)-(S)-mbpam}2] (8) (R = 2,6-Me2C6H3O) by reaction with the corresponding 2,6-dimethylphenol. The structures of the complexes were determined by spectroscopic methods, and the X-ray crystal structures of 2, 6 and 7 were also established. Five-coordinate compounds 1-8 were evaluated as initiators in the ring-opening polymerization of rac-lactide. Compound 5 was also evaluated in the presence of a co-initiator. Finally, a study of the block and random copolymerization of ε-caprolactone and L-lactide was carried out.

KW - Aluminum

KW - Caproates

KW - Catalysis

KW - Dioxanes

KW - Lactones

KW - Models, Molecular

KW - Molecular Structure

KW - Organometallic Compounds

KW - Polymerization

U2 - 10.1039/c3dt32657h

DO - 10.1039/c3dt32657h

M3 - Article

C2 - 23396578

SN - 1477-9234

VL - 42

SP - 9325

EP - 9337

JO - Dalton Transactions

JF - Dalton Transactions

IS - 25

ER -