1
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Tansky M, Comito RJ. Bimetallic polymerization of lactide with binaphthol-derived bis-heteroscorpionate dizinc and dimagnesium complexes. Dalton Trans 2023. [PMID: 37318380 DOI: 10.1039/d3dt00592e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Discrete bimetallic catalysts often provide enhanced reactivity and selectivity in lactone polymerization, making metal-metal cooperativity an important design principle for new catalyst development. However, the poor modularity of binucleating ligands limits structure-reactivity analysis and optimization. This report describes a modular, binucleating bis(pyrazolyl)alkane ligand series (1-R) bridged by a chiral binaphthol unit, prepared by nucleophile-catalyzed condensation between a dialdehyde and a bis(pyrazolyl)methanone. A bis(ethylzinc) complex was characterized by single-crystal X-ray diffraction, but in situ complexation with Zn(HMDS)2 and Mg(HMDS)2 provided more active catalysts for lactide polymerization (HMDS- = hexamethyldisilazide). Structure-reactivity studies identified complexes of 1-Me2 as the most active, and these catalysts show significant enhancements in rate compared to their monometallic analogues. Kinetic analysis resulted in first-order dependence on both mono- and bimetallic catalysts, suggesting metal-metal cooperativity as the basis for this rate enhancement. End-group analysis and low dispersity implicate a coordination-insertion mechanism through an alkoxide. Despite rapid transesterification observed by MALDI, we still demonstrated controlled polymerization in the block copolymerization of ε-caprolactone and L-lactide. Although we observed rate differences in the polymerization of L-lactide by opposite enantiomer catalysts, we did not observe catalyst-directed stereoselectivity in the polymerization of rac- or meso-lactide.
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Affiliation(s)
- Maxym Tansky
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
| | - Robert J Comito
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
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2
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Tannoux T, Auffrant A. Complexes featuring tridentate iminophosphorane ligands: Synthesis, reactivity, and catalysis. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.214845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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3
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de Frémont P, Adet N, Parmentier J, Xu X, Jacques B, Dagorne S. Cationic organometallic complexes of group 12 metals: A decade of progress toward the quest of novel Lewis acidic catalysts. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Gu Z, Comito RJ. Binucleating Bis(pyrazolyl)alkane Ligands and Their Cationic Dizinc Complexes: Modular, Bimetallic Catalysts for Ring-Opening Polymerization. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zipeng Gu
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, United States
| | - Robert J. Comito
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, United States
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5
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Hu M, Song X, Wang F, Zhang W, Ma W, Han F. Ring-opening polymerization of rac-lactide catalyzed by magnesium and zinc complexes supported by an NNO ligand. NEW J CHEM 2022. [DOI: 10.1039/d1nj05157a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Preparation of magnesium and zinc complexes containing unsymmetric tertiary amine ligands and their catalytic properties for polymerization of rac-lactide.
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Affiliation(s)
- Minggang Hu
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
- Heilongjiang Provincial Key Laboratory of Catalytic Synthesis for Fine Chemicals, Qiqihar University, Qiqihar, 161006, China
| | - Xinfeng Song
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Fugui Wang
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Wenzhi Zhang
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Wenhui Ma
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
| | - Fuzhong Han
- College of Chemistry and Chemical Engineering, Qiqihar University, Qiqihar, 161006, China
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6
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Huse K, Wölper C, Schulz S. Synthesis, Reactivity, and Lewis Acidity of Cationic Zinc Complexes. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kevin Huse
- Institute for Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (Cenide), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Christoph Wölper
- Institute for Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (Cenide), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Stephan Schulz
- Institute for Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (Cenide), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
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7
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Jha VK, Das S, Subramaniyan V, Guchhait T, Dakua KK, Mishra S, Mani G. Synthesis, structural characterization, and bonding analysis of two-coordinate copper(I) and silver(I) complexes of pyrrole-based bis(phosphinimine): new metal-pyrrole ring π-interactions. Dalton Trans 2021; 50:8036-8044. [PMID: 34013307 DOI: 10.1039/d1dt01091c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The reaction between 2,5-bis(diphenylphosphinomethyl)pyrrole and Me3SiN3 gave the new pyrrole-based bis(phosphinimine) L1H in an excellent yield. L1H reacts with [CuCl(COD)]2, AgBF4, or AgOTf to give the corresponding two-coordinate mononuclear ionic complex formulated as [M{(L1H)-κ2N,N}]+[X]- where M = Cu and Ag; X = [CuCl2], BF4 or OTf. Their single crystal X-ray diffraction studies confirmed the two-coordinate geometry formed by the chelate bonding mode of L1H. These 10-membered metalacycles exhibit planar chirality and were also characterized by spectroscopic methods. In addition, in all three structures, there exists a hitherto unknown π-interaction between the pyrrole ring atoms and metal, represented as η2-(Cα-N) in the copper(i) complex, and η3-(Cα-N-Cα') in the silver(i) complexes. These weak interactions were supported by DFT calculations in terms of their electron densities, non-covalent interaction plots and the decrease in the aromaticity of the pyrrole ring.
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Affiliation(s)
- Vikesh Kumar Jha
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Sanghamitra Das
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Vasudevan Subramaniyan
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Tapas Guchhait
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Kishan Kumar Dakua
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Sabyashachi Mishra
- Department of Chemistry and Centre for Computational and Data Sciences, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
| | - Ganesan Mani
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721 302, India.
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8
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Friedrich A, Eyselein J, Langer J, Harder S. Comparison of Magnesium and Zinc in Cationic π-Arene and Halobenzene Complexes. Organometallics 2021. [DOI: 10.1021/acs.organomet.0c00786] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander Friedrich
- Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Jonathan Eyselein
- Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Jens Langer
- Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Sjoerd Harder
- Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
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9
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Schäfer PM, Herres-Pawlis S. Robust Guanidine Metal Catalysts for the Ring-Opening Polymerization of Lactide under Industrially Relevant Conditions. Chempluschem 2020; 85:1044-1052. [PMID: 32449840 DOI: 10.1002/cplu.202000252] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 04/30/2020] [Indexed: 01/21/2023]
Abstract
The increasing awareness of sustainability has led to enormous growth of the demand for bio-based and biodegradable polymers such as poly(lactide) (PLA). In industry, polymerization of lactide is currently carried out using tin catalysts (e. g., tin(II) ethyl hexanoate, Sn(Oct)2 ). Since the catalyst remains in the polymer, it can accumulate in the soil or in the human body after degradation and cause damage due to its toxicity. Therefore, a search for a suitable substitute for this catalyst has been going on for decades. Guanidine metal complexes prove to be excellent catalysts in the polymerization of lactide. They are not only convincing because of their activity and the synthesis of high molar mass polymers, but also show a high robustness against high temperatures, oxidation as well as residual protic impurities in the monomer. Herein, key zinc and iron guanidine complexes are discussed with respect to their apparent rate constant (kapp ) and rate constant of propagation (kp ), produced molar masses and the mechanism involved.
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Affiliation(s)
- Pascal M Schäfer
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
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10
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Guillet GL, Pitts SL, Sheriff KW, Rucker DN, Rogers AL. Synthesis, characterization, and crystal structures of organonickel(II) complexes coordinated to novel 1-bromo-2,6-bis{[(λ 5-phosphanylidene)imino]methyl}benzene NCN-pincer ligands. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2019; 75:1381-1388. [PMID: 31589154 DOI: 10.1107/s2053229619012038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 08/30/2019] [Indexed: 11/10/2022]
Abstract
A novel family of four 1-bromo-2,6-bis{[(λ5-phosphanylidene)imino]methyl}benzene ligands has been synthesized and characterized. The phosphiniminomethyl substituents are decorated with either three phenyl groups, two phenyl and one cyclohexyl group, one phenyl and two cyclohexyl groups, or three cyclohexyl groups. Each ligand was metallated using zero-valent nickel through an oxidative addition to form a family of organonickel(II) complexes, namely (2,6-bis{[(triphenyl-λ5-phosphanylidene)imino]methyl}phenyl-κ3N,C1,N')bromidonickel(II) dichloromethane hemisolvate, [NiBr(C44H37N2P2)]·0.5CH2Cl2, (2,6-bis{[(cyclohexyldiphenyl-λ5-phosphanylidene)imino]methyl}phenyl-κ3N,C1,N')bromidonickel(II) diethyl ether hemisolvate, [NiBr(C44H49N2P2)]·0.5C4H10O, (2,6-bis{[(dicyclohexylphenyl-λ5-phosphanylidene)imino]methyl}phenyl-κ3N,C1,N')bromidonickel(II), [NiBr(C44H61N2P2)], and (2,6-bis{[(tricyclohexyl-λ5-phosphanylidene)imino]methyl}phenyl-κ3N,C1,N')bromidonickel(II), [NiBr(C44H73N2P2)]. This family of complexes represents a useful opportunity to investigate the impact of incrementally changing the steric characteristics of a complex on its structure and reactivity.
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Affiliation(s)
- Gary L Guillet
- Department of Chemistry and Biochemistry, Georgia Southern University, Armstrong Campus, 11935 Abercorn St, Savannah, GA 31419, USA
| | - Skyler L Pitts
- Department of Chemistry and Biochemistry, Georgia Southern University, Armstrong Campus, 11935 Abercorn St, Savannah, GA 31419, USA
| | - Kirkland W Sheriff
- Department of Chemistry and Biochemistry, Georgia Southern University, Armstrong Campus, 11935 Abercorn St, Savannah, GA 31419, USA
| | - Donna N Rucker
- Department of Chemistry and Biochemistry, Georgia Southern University, Armstrong Campus, 11935 Abercorn St, Savannah, GA 31419, USA
| | - Aaryn L Rogers
- Department of Chemistry and Biochemistry, Georgia Southern University, Armstrong Campus, 11935 Abercorn St, Savannah, GA 31419, USA
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11
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Quinlivan PJ, Shlian DG, Amemiya E, Parkin G. Reactivity of the carbodiphosphorane, (Ph 3P) 2C, towards main group metal alkyl compounds: coordination and cyclometalation. Dalton Trans 2019; 48:9139-9151. [PMID: 31145405 DOI: 10.1039/c9dt00678h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The carbodiphosphorane, (Ph3P)2C, reacts with Me3Al and Me3Ga to afford the adducts, [(Ph3P)2C]AlMe3 and [(Ph3P)2C]GaMe3, which have been structurally characterized by X-ray diffraction. (Ph3P)2C also reacts with Me2Zn and Me2Cd to generate an adduct but the formation is reversible on the NMR time scale. At elevated temperatures, however, elimination of methane and cyclometalation occurs to afford [κ2-Ph3PC{PPh2(C6H4)}]ZnMe and [κ2-Ph3PC{PPh2(C6H4)}]CdMe. Analogous cyclometalated products, [κ2-Ph3P{CPPh2(C6H4)}]ZnN(SiMe3)2 and [κ2-Ph3P{CPPh2(C6H4)}]CdN(SiMe3)2, are also obtained upon reaction of (Ph3P)2C with Zn[N(SiMe3)2]2 and Cd[N(SiMe3)2]2. The magnesium compounds, Me2Mg and {Mg[N(SiMe3)2]2}2, likewise react with (Ph3P)2C to afford cyclometalated derivatives, namely [κ2-Ph3PC{PPh2(C6H4)}]MgN(SiMe3)2 and {[κ2-Ph3PC{PPh2(C6H4)}]MgMe}2. While this reactivity is similar to the zinc system, the magnesium methyl complex is a dimer with bridging methyl groups, whereas the zinc complex is a monomer. The greater tendency of the methyl groups to bridge magnesium centers rather than zinc centers is supported by density functional theory calculations.
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Affiliation(s)
- Patrick J Quinlivan
- Department of Chemistry, Columbia University, New York, New York 10027, USA.
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12
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Karmakar M, Basak T, Chattopadhyay S. Phosphatase-mimicking activity of a unique penta-nuclear zinc(ii) complex with a reduced Schiff base ligand: assessment of its ability to sense nitroaromatics. NEW J CHEM 2019. [DOI: 10.1039/c8nj06549g] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A penta-nuclear zinc(ii) complex has been synthesized and characterized. The complex has shown good phosphatase-mimicking activity, which has been evaluated spectrophotometrically. The complex also behaves as a sensor for the detection of nitroaromatics via turn-off fluorescence response.
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Affiliation(s)
- Mainak Karmakar
- Department of Chemistry
- Inorganic Section
- Jadavpur University
- Kolkata – 700032
- India
| | - Tanmoy Basak
- Department of Chemistry
- Inorganic Section
- Jadavpur University
- Kolkata – 700032
- India
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13
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Chambenahalli R, Andrews AP, Ritter F, Okuda J, Venugopal A. Terminal hydridozinc cation. Chem Commun (Camb) 2019; 55:2054-2057. [DOI: 10.1039/c8cc09839e] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Thermally stable hydridozinc cation catalytically converts CO2 to PhSi(OCHO)3 using PhSiH3 in the presence of a mild Lewis acid BPh3.
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Affiliation(s)
- Raju Chambenahalli
- School of Chemistry
- Indian Institute of Science Education and Research Thiruvananthapuram
- Thiruvananthapuram 695551
- India
| | - Alex P. Andrews
- School of Chemistry
- Indian Institute of Science Education and Research Thiruvananthapuram
- Thiruvananthapuram 695551
- India
| | - Florian Ritter
- Institute of Inorganic Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| | - Jun Okuda
- Institute of Inorganic Chemistry
- RWTH Aachen University
- 52056 Aachen
- Germany
| | - Ajay Venugopal
- School of Chemistry
- Indian Institute of Science Education and Research Thiruvananthapuram
- Thiruvananthapuram 695551
- India
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14
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Schäfer PM, McKeown P, Fuchs M, Rittinghaus RD, Hermann A, Henkel J, Seidel S, Roitzheim C, Ksiazkiewicz AN, Hoffmann A, Pich A, Jones MD, Herres-Pawlis S. Tuning a robust system: N,O zinc guanidine catalysts for the ROP of lactide. Dalton Trans 2019; 48:6071-6082. [PMID: 30758389 DOI: 10.1039/c8dt04938f] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Non-toxic, highly active and robust complexes are the holy grail as ideal green catalysts for the polymerisation of biorenewable and biodegradable polylactide. Four new zinc guanidine complexes [ZnCl2(TMG4NMe2asme)], [ZnCl2(TMG5Clasme)], [ZnCl2(TMG5Measme)] and [ZnCl2(TMG5NMe2asme)] with different electron-donating and electron-withdrawing groups on the ligand's aromatic backbone have been synthesised. Ligands are derived from low-cost commercially available compounds and have been converted by a three- or four-step synthesis process into the desired ligand in good yields. The compounds have been fully characterised and tested in the ROP of rac-LA under industrially relevant conditions. The complexes are based on the recently published structure [ZnCl2(TMGasme)] which has shown high activity in the polymerisation of lactide at 150 °C. Different substituents in the para-position of the guanidine moiety significantly increase the polymerisation rate whereas positioning substituents in the meta-position causes no change in the reaction rate. With molecular weights over 71 000 g mol-1 being achievable, the best system produces polymers for multiple industrial applications and its polymerisation rate approaches that of Sn(Oct)2. The robust systems are able to polymerise non-purified lactide. The initiation of the polymerisation is suggested to occur due to impurities in the monomer.
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Affiliation(s)
- Pascal M Schäfer
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany.
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15
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Kang MS, Cho J, Nayab S, Jeong JH. Synthesis and characterization of Zn(II) and Cu(II) complexes bearing (chiral substituent)(diethyl)-ethanediamine derivatives as precatalysts for rac-lactide polymerisation. Polyhedron 2019. [DOI: 10.1016/j.poly.2018.10.068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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16
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Cho J, Chun MK, Nayab S, Jeong JH. Synthesis, characterisation, and X-ray structures of zinc(II) complexes bearing camphor-based ethyleneamineimines as pre-catalysts for heterotactic-enriched polylactide from rac-lactide. TRANSIT METAL CHEM 2018. [DOI: 10.1007/s11243-018-0282-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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17
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Newland RJ, Delve MP, Wingad RL, Mansell SM. Two isomers of a bis(diphenylphosphino)phosphinine, and the synthesis and reactivity of Ru arene/Cp* phosphinophosphinine complexes. NEW J CHEM 2018. [DOI: 10.1039/c8nj03632b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Two isomers of a bis(diphenylphosphino)phosphinine have been synthesised, and the Ru coordination chemistry of a 2-phosphinophosphinine extended to include reactions of H2O across a PC double bond.
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18
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Metz A, McKeown P, Esser B, Gohlke C, Kröckert K, Laurini L, Scheckenbach M, McCormick SN, Oswald M, Hoffmann A, Jones MD, Herres-Pawlis S. ZnII
Chlorido Complexes with Aliphatic, Chiral Bisguanidine Ligands as Catalysts in the Ring-Opening Polymerisation of rac
-Lactide Using FT-IR Spectroscopy in Bulk. Eur J Inorg Chem 2017. [DOI: 10.1002/ejic.201701147] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Angela Metz
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Paul McKeown
- Centre for Sustainable Chemical Technologies; Department of Chemistry; University of Bath; Claverton Down BA2 7AY Bath United Kingdom
| | - Bastian Esser
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Clara Gohlke
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Konstantin Kröckert
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Larissa Laurini
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Michael Scheckenbach
- Department of Chemistry and Pharmacy; Ludwig-Maximlians University Munich; Butenandtstraße 5-13 81377 Munich Germany
| | - Strachan N. McCormick
- Centre for Sustainable Chemical Technologies; Department of Chemistry; University of Bath; Claverton Down BA2 7AY Bath United Kingdom
| | - Michaela Oswald
- Department of Chemistry and Pharmacy; Ludwig-Maximlians University Munich; Butenandtstraße 5-13 81377 Munich Germany
| | - Alexander Hoffmann
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
| | - Matthew D. Jones
- Centre for Sustainable Chemical Technologies; Department of Chemistry; University of Bath; Claverton Down BA2 7AY Bath United Kingdom
| | - Sonja Herres-Pawlis
- Institute of Inorganic Chemistry; RWTH Aachen University; Landoltweg 1 52074 Germany
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19
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Reactivity of Zinc Halide Complexes Containing Camphor-Derived Guanidine Ligands with Technical rac-Lactide. INORGANICS 2017. [DOI: 10.3390/inorganics5040085] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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20
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Schäfer PM, Fuchs M, Ohligschläger A, Rittinghaus R, McKeown P, Akin E, Schmidt M, Hoffmann A, Liauw MA, Jones MD, Herres-Pawlis S. Highly Active N,O Zinc Guanidine Catalysts for the Ring-Opening Polymerization of Lactide. CHEMSUSCHEM 2017; 10:3547-3556. [PMID: 28779508 DOI: 10.1002/cssc.201701237] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 08/04/2017] [Indexed: 06/07/2023]
Abstract
New zinc guanidine complexes with N,O donor functionalities were prepared, characterized by X-Ray crystallography, and examined for their catalytic activity in the solvent-free ring-opening polymerization (ROP) of technical-grade rac-lactide at 150 °C. All complexes showed a high activity. The fastest complex [ZnCl2 (DMEGasme)] (C1) produced colorless poly(lactide) (PLA) after 90 min with a conversion of 52 % and high molar masses (Mw =69 100, polydispersity=1.4). The complexes were tested with different monomer-to-initiator ratios to determine the rate constant kp . Furthermore, a polymerization with the most active complex C1 was monitored by in situ Raman spectroscopy. Overall, conversion of up to 90 % can be obtained. End-group analysis was performed to clarify the mechanism. All four complexes combine robustness against impurities in the lactide with high polymerization rates, and they represent the fastest robust lactide ROP catalysts to date, opening new avenues to a sustainable ROP catalyst family for industrial use.
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Affiliation(s)
- Pascal M Schäfer
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Martin Fuchs
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Andreas Ohligschläger
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Ruth Rittinghaus
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Paul McKeown
- Department of Chemistry, University of Bath, ClavertonDown, Bath, BA2 7AY, UK
| | - Enver Akin
- Fakultät für Naturwissenschaften, Department Chemie, Universität Paderborn, Warburger Strasse 100, 33098, Paderborn, Germany
| | - Maximilian Schmidt
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Alexander Hoffmann
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
| | - Marcel A Liauw
- Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Matthew D Jones
- Department of Chemistry, University of Bath, ClavertonDown, Bath, BA2 7AY, UK
| | - Sonja Herres-Pawlis
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany
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21
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Chakraborty D, Chokkapu ER, Mandal M, Gowda RR, Ramkumar V. Zwitterionic Complexes of Group 4 Metal Chlorides Containing a Bis(imino)phenoxide Scaffold: Synthesis, Characterization and Polymerization Studies. ChemistrySelect 2016. [DOI: 10.1002/slct.201600909] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Debashis Chakraborty
- Department of Chemistry; Indian Institute of Technology Madras; Chennai-600 036, Tamil Nadu India
| | - Eswara Rao Chokkapu
- Department of Chemistry; Indian Institute of Technology Madras; Chennai-600 036, Tamil Nadu India
| | - Mrinmay Mandal
- Department of Chemistry; Indian Institute of Technology Patna; Patna-800 013, Bihar India
| | - Ravikumar R. Gowda
- Department of Chemistry; Indian Institute of Technology Madras; Chennai-600 036, Tamil Nadu India
| | - Venkatachalam Ramkumar
- Department of Chemistry; Indian Institute of Technology Madras; Chennai-600 036, Tamil Nadu India
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22
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Anga S, Bhattacharjee J, Banerjee I, Nayek HP, Panda TK. Calcium Complexes Having Different Amidinate Ligands - Synthesis and Structural Diversity. ChemistrySelect 2016. [DOI: 10.1002/slct.201600299] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Srinivas Anga
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi - 502 285 Sangareddy, Telangana India
| | - Jayeeta Bhattacharjee
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi - 502 285 Sangareddy, Telangana India
| | - Indrani Banerjee
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi - 502 285 Sangareddy, Telangana India
| | - Hari Pada Nayek
- Department of Applied Chemistry; Indian School of Mines, Dhanbad; 826004 Jharkhand India
| | - Tarun K. Panda
- Department of Chemistry; Indian Institute of Technology Hyderabad; Kandi - 502 285 Sangareddy, Telangana India
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23
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Roy S, Bauza A, Frontera A, Schaper F, Banik R, Purkayastha A, Reddy BM, Sridhar B, Drew MG, Das SK, Das S. Structural diversity and non-covalent interactions in Cd(II) and Zn(II) complexes derived from 3,5-dinitrobenzoic acid and pyridine: Experimental and theoretical aspects. Inorganica Chim Acta 2016. [DOI: 10.1016/j.ica.2015.10.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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24
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Hänninen MM, Zamora MT, MacNeil CS, Knott JP, Hayes PG. Elucidation of the resting state of a rhodium NNN-pincer hydrogenation catalyst that features a remarkably upfield hydride 1H NMR chemical shift. Chem Commun (Camb) 2016; 52:586-9. [DOI: 10.1039/c5cc08348f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Rhodium(i) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes. The terminal or resting state of the catalyst, which exhibits an unusually upfield Rh–hydride 1H NMR chemical shift, has been identified.
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Affiliation(s)
- Mikko M. Hänninen
- Department of Chemistry and Biochemistry
- University of Lethbridge
- Lethbridge
- Canada
| | - Matthew T. Zamora
- Department of Chemistry and Biochemistry
- University of Lethbridge
- Lethbridge
- Canada
| | - Connor S. MacNeil
- Department of Chemistry and Biochemistry
- University of Lethbridge
- Lethbridge
- Canada
| | - Jackson P. Knott
- Department of Chemistry and Biochemistry
- University of Lethbridge
- Lethbridge
- Canada
| | - Paul G. Hayes
- Department of Chemistry and Biochemistry
- University of Lethbridge
- Lethbridge
- Canada
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25
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Döring A, Flörke U, Hoffmann A, Jones MD, Kuckling D, Michaelis de Vasconcellos J, Herres-Pawlis S. Zinc Complexes with Guanidine-Pyridine Hybrid Ligands: Anion Effect and Catalytic Activity. Z Anorg Allg Chem 2015. [DOI: 10.1002/zaac.201500538] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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26
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Sarazin Y, Carpentier JF. Discrete Cationic Complexes for Ring-Opening Polymerization Catalysis of Cyclic Esters and Epoxides. Chem Rev 2015; 115:3564-614. [DOI: 10.1021/acs.chemrev.5b00033] [Citation(s) in RCA: 211] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yann Sarazin
- Institut des Sciences Chimiques
de Rennes, Organometallics, Materials and Catalysis Laboratories,
UMR 6226 CNRS, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex, France
| | - Jean-François Carpentier
- Institut des Sciences Chimiques
de Rennes, Organometallics, Materials and Catalysis Laboratories,
UMR 6226 CNRS, Université de Rennes 1, Campus de Beaulieu, F-35042 Rennes Cedex, France
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27
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Gossage RA. Pincer Complexes of Lithium, Sodium, Magnesium and Related Metals: A Discussion of Solution and Solid-State Aggregated Structure and Reactivity. TOP ORGANOMETAL CHEM 2015. [DOI: 10.1007/3418_2015_119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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28
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McGrew GI, Khatri PA, Geiger WE, Kemp RA, Waterman R. Unexpected formal insertion of CO2 into the C–Si bonds of a zinc compound. Chem Commun (Camb) 2015; 51:15804-7. [DOI: 10.1039/c5cc06910f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A formal insertion of CO2 into the C–Si bond of zinc compound has been observed under mild conditions.
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Affiliation(s)
| | | | | | - Richard A. Kemp
- Department of Chemistry and Chemical Biology
- University of New Mexico
- Albuquerque
- USA
- Advanced Materials Laboratory
| | - Rory Waterman
- Department of Chemistry
- University of Vermont
- Burlington
- USA
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29
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Chilleck MA, Hartenstein L, Braun T, Roesky PW, Braun B. Cationic Zinc Organyls as Precatalysts for Hydroamination Reactions. Chemistry 2014; 21:2594-602. [DOI: 10.1002/chem.201405662] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Indexed: 11/08/2022]
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30
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Kwon KS, Nayab S, Lee H, Jeong JH. Synthesis and structural characterisation of zinc complexes bearing furanylmethyl and thiophenylmethyl derivatives of (R,R)-1,2-diaminocyclohexanes for stereoselective polymerisation of poly(rac-lactide). Polyhedron 2014. [DOI: 10.1016/j.poly.2014.03.055] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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31
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Scheiper C, Schulz S, Wölper C, Bläser D, Roll J. Synthesis and Single Crystal X-ray Structures of Cationic Zincβ-Diketiminate Complexes. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300119] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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32
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Eckert PK, Vieira IDS, Gessner VH, Börner J, Strohmann C, Herres-Pawlis S. Simple is best: Diamine zinc complexes as unexpected catalysts in lactide polymerisation. Polyhedron 2013. [DOI: 10.1016/j.poly.2012.09.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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33
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dos Santos Vieira I, Dietz C, Mohr F, Beckert R, Herres-Pawlis S. Oxalic Amidines - Protonation Studies and Activity in Lactide Polymerisation. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200838] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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34
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Lichtenberg C, Spaniol TP, Okuda J. Dimerization of the Allylzinc Cation: Selective Coupling of Allyl Anions in a Metallo-Ene Reaction. Angew Chem Int Ed Engl 2012; 51:8101-5. [DOI: 10.1002/anie.201203698] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Indexed: 11/12/2022]
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35
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Lichtenberg C, Spaniol TP, Okuda J. Dimerisierung des Allylzink-Kations: selektive Kupplung von Allylanionen in einer Metallo-En-Reaktion. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203698] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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36
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β-Diketiminato-Alkaline Earth Cationic Complexes: Synthesis, Structures, Lactide Polymerization and Unusual Oxidative Reactivity of the Ancillary Ligand. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200183] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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37
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Wheaton CA, Hayes PG. Electron deficient zinc complexes: Enhanced lactide polymerization activity achieved through rational ligand design. J Organomet Chem 2012. [DOI: 10.1016/j.jorganchem.2012.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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38
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dos Santos Vieira I, Herres‐Pawlis S. Lactide Polymerisation with Complexes of Neutral N‐Donors – New Strategies for Robust Catalysts. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201101131] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ines dos Santos Vieira
- Fakultät Chemie, Anorganische Chemie, Technische Universität Dortmund, 44221 Dortmund, German, Fax: +49‐231‐7555048
| | - Sonja Herres‐Pawlis
- Fakultät Chemie, Anorganische Chemie, Technische Universität Dortmund, 44221 Dortmund, German, Fax: +49‐231‐7555048
- Present address: Fakultät für Chemie und Pharmazie, Department Chemie, Ludwig‐Maximilians‐Universität München, Butenandtstr. 5–13, 81377 München, Germany, Fax: +49‐89‐218077867
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39
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Sun H, Ritch JS, Hayes PG. Ring-opening polymerisation of rac-lactide mediated by cationic zinc complexes featuring P-stereogenic bisphosphinimine ligands. Dalton Trans 2012; 41:3701-13. [DOI: 10.1039/c2dt11954d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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40
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Wheaton CA, Hayes PG. Exploring the versatility of a bis(phosphinimine) pincer ligand: effect of sterics on structure and lactide polymerization activity of cationic zinc complexes. Catal Sci Technol 2012. [DOI: 10.1039/c1cy00306b] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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41
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Ring opening polymerization of l-lactide by an electron-rich Schiff base zinc complex: An activity and kinetic study. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.molcata.2011.10.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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42
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Liu B, Roisnel T, Sarazin Y. Well-defined, solvent-free cationic barium complexes: Synthetic strategies and catalytic activity in the ring-opening polymerization of lactide. Inorganica Chim Acta 2012. [DOI: 10.1016/j.ica.2011.09.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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43
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Wheaton CA, Ireland BJ, Hayes PG. Synthesis and Structural Diversity of ZnCl2 and Zn(C6F5)2 Complexes of a Phosphinimine Ligand. Z Anorg Allg Chem 2011. [DOI: 10.1002/zaac.201100355] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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44
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Börner J, dos Santos Vieira I, Jones MD, Döring A, Kuckling D, Flörke U, Herres-Pawlis S. Zinc Complexes with Guanidine-Pyridine Hybrid Ligands - Guanidine Effect and Catalytic Activity. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201100540] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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45
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Sun H, Ritch JS, Hayes PG. Toward Stereoselective Lactide Polymerization Catalysts: Cationic Zinc Complexes Supported by a Chiral Phosphinimine Scaffold. Inorg Chem 2011; 50:8063-72. [DOI: 10.1021/ic201139b] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hongsui Sun
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada
| | - Jamie S. Ritch
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada
| | - Paul G. Hayes
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada
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46
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Synthesis and characterization of aluminum and zinc complexes supported by pyrrole-based ligands and catalysis of the aluminum complexes toward the ring-opening polymerization of ɛ-caprolactone. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.04.028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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47
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Giffin NA, Hendsbee AD, Masuda JD. Rhodium carbonyl complexes of bulky, anionic nitrogen-based ligands: A comparison of donating ability. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.03.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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48
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Liang L, Tsai T, Li C, Hsu Y, Lee T. Synthesis, Structure, and Ring‐Opening Polymerization Catalysis of Zinc Complexes Containing Amido Phosphinimine Ligands. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201001362] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Lan‐Chang Liang
- Department of Chemistry and Center for Nanoscience &Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Tzung‐Ling Tsai
- Department of Chemistry and Center for Nanoscience &Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Chun‐Wei Li
- Department of Chemistry and Center for Nanoscience &Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Yu‐Lin Hsu
- Department of Chemistry and Center for Nanoscience &Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Ting‐Yu Lee
- Department of Applied Chemistry, National University of Kaohsiung, Kaohsiung 81148, Taiwan
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49
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Sarazin Y, Liu B, Roisnel T, Maron L, Carpentier JF. Discrete, solvent-free alkaline-earth metal cations: metal···fluorine interactions and ROP catalytic activity. J Am Chem Soc 2011; 133:9069-87. [PMID: 21545119 DOI: 10.1021/ja2024977] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Efficient protocols for the syntheses of well-defined, solvent-free cations of the large alkaline-earth (Ae) metals (Ca, Sr, Ba) and their smaller Zn and Mg analogues have been designed. The reaction of 2,4-di-tert-butyl-6-(morpholinomethyl)phenol ({LO(1)}H), 2-{[bis(2-methoxyethyl)amino]methyl}-4,6-di-tert-butylphenol ({LO(2)}H), 2-[(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)methyl]-4,6-di-tert-butylphenol ({LO(3)}H), and 2-[(1,4,7,10-tetraoxa-13-azacyclo-pentadecan-13-yl)methyl]-1,1,1,3,3,3-hexafluoropropan-2-ol ({RO(3)}H) with [H(OEt(2))(2)](+)[H(2)N{B(C(6)F(5))(3)}(2)](-) readily afforded the doubly acidic pro-ligands [{LO(1)}HH](+)[X](-) (1), [{LO(2)}HH](+)[X](-) (2), [{LO(3)}HH](+)[X](-) (3), and [{RO(3)}HH](+)[X](-) (4) ([X](-) = [H(2)N{B(C(6)F(5))(3)}(2)](-)). The addition of 2 to Ca[N(SiMe(3))(2)](2)(THF)(2) and Sr[N(SiMe(3))(2)](2)(THF)(2) yielded [{LO(2)}Ca(THF)(0.5)](+)[X](-) (5) and [{LO(2)}Sr(THF)](+)[X](-) (6), respectively. Alternatively, 5 could also be prepared upon treatment of {LO(2)}CaN(SiMe(3))(2) (7) with [H(OEt(2))(2)](+)[X](-). Complexes [{LO(3)}M](+)[X](-) (M = Zn, 8; Mg, 9; Ca, 10; Sr, 11; Ba, 12) and [{RO(3)}M](+)[X](-) (M = Zn, 13; Mg, 14; Ca, 15; Sr, 16; Ba, 17) were synthesized in high yields (70-90%) by reaction of 3 or 4 with the neutral precursors M[N(SiMe(3))(2)](2)(THF)(x) (M = Zn, Mg, x = 0; M = Ca, Sr, Ba, x = 2). All compounds were fully characterized by spectroscopic methods, and the solid-sate structures of compounds 1, 3, 7, 8, 13, 14, {15}(4)·3CD(2)Cl(2), {16}(4)·3CD(2)Cl(2), and {{17}(4)·EtOH}·3CD(2)Cl(2) were determined by X-ray diffraction crystallography. Whereas the complexes are monomeric in the case of Zn and Mg, they form bimetallic cations in the case of Ca, Sr and Ba; there is no contact between the metal and the weakly coordinating anion. In all metal complexes, the multidentate ligand is κ(6)-coordinated to the metal. Strong intramolecular M···F secondary interactions between the metal and F atoms from the ancillary ligands are observed in the structures of {15}(4)·3CD(2)Cl(2), {16}(4)·3CD(2)Cl(2), and {{17}(4)·EtOH}·3CD(2)Cl(2). VT (19)F{(1)H} NMR provided no direct evidence that these interactions are maintained in solution; nevertheless, significant Ae···F energies of stabilization of 25-26 (Ca, Ba) and 40 kcal·mol(-1) (Sr) were calculated by NBO analysis on DFT-optimized structures. The identity and integrity of the cationic complexes are preserved in solution in the presence of an excess of alcohol (BnOH, (i)PrOH) or L-lactide (L-LA). Efficient binary catalytic systems for the immortal ring-opening polymerization of L-LA (up to 3,000 equiv) are produced upon addition of an excess (5-50 equiv) of external protic nucleophilic agents (BnOH, (i)PrOH) to 8-12 or 13-17. PLLAs with M(n) up to 35,000 g·mol(-1) were produced in a very controlled fashion (M(w)/M(n) ≈ 1.10-1.20) and without epimerization. In each series of catalysts, the following order of catalytic activity was established: Mg ≪ Zn < Ca < Sr ≈ Ba; also, Ae complexes supported by the aryloxide ligand are more active than their parents supported by the fluorinated alkoxide ancillary, possibly owing to the presence of Ae···F interactions in the latter case. The rate law -d[L-LA]/dt = k(p)·[L-LA](1.0)·[16](1.0)·[BnOH](1.0) was established by NMR kinetic investigations, with the corresponding activation parameters ΔH(++) = 14.8(5) kcal·mol(-1) and ΔS(++) = -7.6(2.0) cal·K(-1)·mol(-1). DFT calculations indicated that the observed order of catalytic activity matches an increase of the L-LA coordination energy onto the cationic metal centers with parallel decrease of the positive metal charge.
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Affiliation(s)
- Yann Sarazin
- UMR 6226 Sciences Chimiques de Rennes, Université de Rennes 1-CNRS, Campus de Beaulieu, 35042 Rennes Cedex, France.
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50
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Wheaton CA, Hayes PG. DESIGNING CATIONIC ZINC AND MAGNESIUM CATALYSTS FOR COORDINATION–INSERTION POLYMERIZATION OF LACTIDE. COMMENT INORG CHEM 2011. [DOI: 10.1080/02603594.2011.634037] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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