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Navrátil M, Císařová I, Štěpnička P. Synthesis and coordination of hybrid phosphinoferrocenes with extended donor pendants. Dalton Trans 2022; 51:14618-14629. [PMID: 36083192 DOI: 10.1039/d2dt02514k] [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
Combining a phosphinoferrocene fragment with extended multidonor moieties affords novel, flexible multidonor pro-ligands. This contribution describes the synthesis of two structurally similar functional phosphines, Ph2PfcNHC(O)CH2PPh2 (1) and Ph2PfcNHCH2CH2PPh2 (2, fc = ferrocene-1,1'-diyl), and their coordination behaviour towards Pd(II). The former amidophosphine reacts with [PdCl2(MeCN)2] to produce the chelate complex [PdCl2(1-κ2P,P')] as a mixture of cis and trans isomers, which convert into bis-chelate [PdCl2(Ph2PfcNC(O)CH2PPh2-κ3P,P',N)] upon reacting with a strong base (KOt-Bu). In contrast, the more flexible and more basic phosphinoamine 2 directly forms the cationic bis-chelate complex [PdCl(2-κ3P,P',N)]Cl via spontaneous self-ionisation. Subsequent halogen abstraction with Ag[SbF6] results either in counter ion exchange to give [PdCl(2-κ3P,P',N)][SbF6] or in the formation of a structurally unique complex [PdCl(2-κ4Fe,P,P',N)][SbF6]2 with an Fe → Pd dative interaction, depending on the amount of silver(I) salt used (1 or 2 equiv.).
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Affiliation(s)
- Michal Navrátil
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Ivana Císařová
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Petr Štěpnička
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
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2
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Synthetic and DFT Modeling Studies on Suzuki–Miyaura Reactions of 4,5-Dibromo-2-methylpyridazin-3(2H)-one with Ferrocene Boronates, Accompanied by Hydrodebromination and a Novel Bridge-Forming Annulation In Vitro Cytotoxic Activity of the Ferrocenyl–Pyridazinone Products. Catalysts 2022. [DOI: 10.3390/catal12060578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
This paper presented the efficiency of different Pd-based catalytic systems in a series of SM reactions of 4,5-dibromo-2-methylpyridazin-3(2H)-one with ferroceneboronic acid, ferrocene-1,1′-diboronoc acid, and its bis-pinacol ester. In addition to the disubstituted product, these transformations afford substantial amounts of isomeric 4- and 5-ferrocenyl-2-methylpyridazin-3(2H)-ones, and a unique asymmetric bi-pyridazinone-bridged ferrocenophane with a screwed molecular architecture. The reactions of phenylboronic acid, conducted under the conditions, are proven to be the most reductive in the conversions of ferroceneboronic acid, and produce 2-methyl-4,5-diphenylpyridazin-3(2H)-one as single product, supporting our view about solvent-mediated hydrodehalogenations that are supposed to proceed via the assistance of the ferrocenyl group present in the reaction mixture, or attached to the bromo-pyridazinone scaffold, which is constructed in the first SM coupling of the heterocyclic precursor. A comparative DFT modelling study on the structures and possible transformations of relevant bromo-, ferrocene- and phenyl-containing carbopalladated intermediate pairs was carried out, providing reasonable mechanisms suitable to account for the apparently surprising regioselectivity of the alternative hydrodebromination processes, and for the formation of the ferrocenophane product. Supporting the results of DFT modelling studies, the implication of DMF as a hydrogen transfer agent in the hydrodebromination reactions is evidenced by deuterium labelling experiments using the solvent mixtures DMF-d7–H2O (4:1) and DMF–D2O (4:1). The organometallic products display antiproliferative effects on human malignant cell lines.
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3
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Hern ZC, Quan SM, Dai R, Lai A, Wang Y, Liu C, Diaconescu PL. ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization. J Am Chem Soc 2021; 143:19802-19808. [PMID: 34792339 DOI: 10.1021/jacs.1c08648] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr(OtBu)2 (salfan = 1,1'-di(2-tert-butyl-6-N-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst's oxidation state and its subsequent monomer (l-lactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly(cyclohexene oxide-b-lactide-b-cyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1-1.5) and molecular weights ranging from 7 to 26 kDa.
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Affiliation(s)
- Zachary C Hern
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Stephanie M Quan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Ruxi Dai
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Amy Lai
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Yihang Wang
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Chong Liu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Paula L Diaconescu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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4
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Navrátil M, Císařová I, Štěpnička P. Synthesis, Coordination and Electrochemistry of a Ferrocenyl‐Tagged Aminobisphosphane Ligand. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Michal Navrátil
- Department of Inorganic Chemistry Faculty of Science Charles University Hlavova 2030 128 40 Prague Czech Republic
| | - Ivana Císařová
- Department of Inorganic Chemistry Faculty of Science Charles University Hlavova 2030 128 40 Prague Czech Republic
| | - Petr Štěpnička
- Department of Inorganic Chemistry Faculty of Science Charles University Hlavova 2030 128 40 Prague Czech Republic
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5
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Hendricks ME, Xu X, Boller TR, Samples EM, Johnson AR, Nataro C. Synthesis, characterization and electrochemistry of [Pd(PP)MeCl] compounds with 1,1′-bis(phosphino)ferrocene ligands. Polyhedron 2021. [DOI: 10.1016/j.poly.2021.115104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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6
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Maity R, Birenheide BS, Breher F, Sarkar B. Cooperative Effects in Multimetallic Complexes Applied in Catalysis. ChemCatChem 2021. [DOI: 10.1002/cctc.202001951] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ramananda Maity
- Department of Chemistry University of Calcutta 92, A. P. C. Road Kolkata 700009 India
| | - Bernhard S. Birenheide
- Institute of Inorganic Chemistry Karlsruhe Institute of Technology (KIT) Engesserstr. 15 76131 Karlsruhe Germany
| | - Frank Breher
- Institute of Inorganic Chemistry Karlsruhe Institute of Technology (KIT) Engesserstr. 15 76131 Karlsruhe Germany
| | - Biprajit Sarkar
- Lehrstuhl für Anorganische Koordinationschemie Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 D 70569 Stuttgart Germany
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7
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Deng S, Diaconescu PL. A switchable dimeric yttrium complex and its three catalytic states in ring opening polymerization. Inorg Chem Front 2021. [DOI: 10.1039/d0qi01479f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A dimeric yttrium phenoxide complex can be oxidized in a stepwise fashion to access three oxidation states. The three states show different activity in the ring opening polymerization of cyclic esters and epoxides.
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Affiliation(s)
- Shijie Deng
- University of California
- Los Angeles
- Department of Chemistry and Biochemistry
- Los Angeles
- USA
| | - Paula L. Diaconescu
- University of California
- Los Angeles
- Department of Chemistry and Biochemistry
- Los Angeles
- USA
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8
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Bárta O, Gyepes R, Císařová I, Alemayehu A, Štěpnička P. Synthesis and study of Fe → Pd interactions in unsymmetric Pd(ii) complexes with phosphinoferrocene guanidine ligands. Dalton Trans 2020; 49:4225-4229. [PMID: 32196051 DOI: 10.1039/d0dt00812e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Readily available phosphinoferrocene guanidines coordinate Pd(ii) as P,N-chelating or κ3P,N,Fe-bound ligands. As the latter, they give rise to the first donor-asymmetric complexes featuring Fe-Pd dative bonds, which were studied using direct (spectroscopic and electrochemical) methods and theoretical (DFT) approaches.
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Affiliation(s)
- Ondřej Bárta
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Róbert Gyepes
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Ivana Císařová
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Adam Alemayehu
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
| | - Petr Štěpnička
- Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic.
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9
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Hatanaka T, Kusunose H, Kawaguchi H, Funahashi Y. Dinitrogen Activation by a Heterometallic VFe Complex Derived from 1,1'‐Bis(arylamido)vanadocene. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201901120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Tsubasa Hatanaka
- Department of Chemistry Graduate School of Science Osaka University 1–1 Machikaneyama 560–0043 Toyonaka Osaka Japan
| | - Hinano Kusunose
- Department of Chemistry Graduate School of Science Osaka University 1–1 Machikaneyama 560–0043 Toyonaka Osaka Japan
| | - Hiroyuki Kawaguchi
- Department of Chemistry Graduate School of Science Tokyo Institute of Technology 2–12–1 Ookayama, Meguro‐ku 152–8551 Tokyo Japan
| | - Yasuhiro Funahashi
- Department of Chemistry Graduate School of Science Osaka University 1–1 Machikaneyama 560–0043 Toyonaka Osaka Japan
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10
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Lai A, Hern ZC, Diaconescu PL. Switchable Ring‐Opening Polymerization by a Ferrocene Supported Aluminum Complex. ChemCatChem 2019. [DOI: 10.1002/cctc.201900747] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Amy Lai
- Department of Chemistry and Biochemistry University of California, Los Angeles 607 Charles E. Young Drive East Los Angeles CA 90095 USA
| | - Zachary C. Hern
- Department of Chemistry and Biochemistry University of California, Los Angeles 607 Charles E. Young Drive East Los Angeles CA 90095 USA
| | - Paula L. Diaconescu
- Department of Chemistry and Biochemistry University of California, Los Angeles 607 Charles E. Young Drive East Los Angeles CA 90095 USA
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11
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Palomero OE, Jones RA. 1,1′-Dicarbodiimidoferrocenes: Synthesis, Characterization, and Group IV 1,1′-Bisguanidinateferrocene Complexes. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00336] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Orhi Esarte Palomero
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - Richard A. Jones
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712-1224, United States
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12
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Shen Y, Shepard SM, Reed CJ, Diaconescu PL. Zirconium complexes supported by a ferrocene-based ligand as redox switches for hydroamination reactions. Chem Commun (Camb) 2019; 55:5587-5590. [PMID: 31020301 DOI: 10.1039/c9cc01076a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The synthesis of (thiolfan*)Zr(NEt2)2 (thiolfan* = 1,1'-bis(2,4-di-tert-butyl-6-thiophenoxy)ferrocene) and its catalytic activity for intramolecular hydroamination are reported. In situ oxidation and reduction of the metal complex results in reactivity towards different substrates. The reduced form of (thiolfan*)Zr(NEt2)2 catalyzes hydroamination reactions of primary aminoalkenes, whereas the oxidized form catalyzes hydroamination reactions of secondary aminoalkenes.
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Affiliation(s)
- Yi Shen
- Department of Chemistry & Biochemistry, University of California, Los Angeles, USA.
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13
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Wei J, Diaconescu PL. Redox-Switchable Ring-Opening Polymerization with Ferrocene Derivatives. Acc Chem Res 2019; 52:415-424. [PMID: 30707548 DOI: 10.1021/acs.accounts.8b00523] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Switchable catalysts incorporate stimuli-responsive features and allow synthetic tasks that are difficult or impossible to accomplish in other ways. They mimic biological processes in that they can provide both spatial and temporal control, unlike most reactions promoted by human-made catalysts that usually occur according to carefully optimized conditions. In the area of switchable catalysis, redox-switchable ring-opening polymerization (ROP) has attracted much attention, emerging as a powerful strategy for the development of environmentally friendly biodegradable copolymers, especially those containing blocks with complementary properties. Controlling the sequence and regularity of each copolymeric building block can affect the material properties significantly since they are directly related to the respective microstructures. Such control can be exerted with a well-designed redox-switchable catalyst by timing the oxidation and reduction events. In highly selective systems, one form of the catalyst reacts with a monomer until the redox state of the catalyst is altered, at which point the altered state of the catalyst reacts with another monomer. The reaction time may be varied from one cycle to another to generate various designer multiblock copolymers. The first instance of redox-mediated ROP was described by N. Long and co-workers in 2006. This example, as well as many early reported redox-switchable catalysts, could only achieve an on/off switch of activity toward a single monomer or substrate. However, our efforts brought on a general strategy for designing redox-switchable metal complexes that can catalyze different reactions in two oxidation states. In recent years, our contributions to this research field led to the synthesis of several multiblock copolymers prepared from biorenewable resources. This Account provides an overview of reported redox-switchable polymerization catalysts that allow for complementary reactivity in different oxidation states and highlights the potential of this strategy in preparing biodegradable materials. First, we define the field of redox-switchable catalysis and illustrate the design and significance of our ferrocene-chelating ligands, in which the oxidation state of iron in ferrocene can control the reactivity of the resulting metal complexes remotely. Next, we illustrate recent advances in the synthesis of new biodegradable copolymers including (1) how to tune the activity of the ROP catalysts by exploring various metal centers and ferrocene-based ligand combinations; (2) how to synthesize new multiblock copolymers of cyclic esters, epoxides, and carbonates by redox-switchable ROP; and (3) how to understand the mechanism of these reactions by discussing both experimental and theoretical investigations. By the application and development of redox-switchable strategies, various novel materials and reactions can be expected in the future.
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Affiliation(s)
- Junnian Wei
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095, United States
| | - Paula L. Diaconescu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095, United States
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14
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Liu X, Chi J, Dong B, Sun Y. Recent Progress in Decoupled H
2
and O
2
Production from Electrolytic Water Splitting. ChemElectroChem 2019. [DOI: 10.1002/celc.201801671] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Xuan Liu
- Department of Chemistry University of Cincinnati Cincinnati OH 45221 USA
| | - Jingqi Chi
- State Key Laboratory of Heavy Oil Processing College of Science China University of Petroleum (East China) Qingdao Shandong 266580 China
| | - Bin Dong
- State Key Laboratory of Heavy Oil Processing College of Science China University of Petroleum (East China) Qingdao Shandong 266580 China
| | - Yujie Sun
- Department of Chemistry University of Cincinnati Cincinnati OH 45221 USA
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15
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Halder P, SantaLucia DJ, Park SV, Berry JF. From Pincer to Paddlewheel: C-H and C-S Bond Activation at Bis(2-pyridylthio)methane by Palladium(II). Inorg Chem 2019; 58:2270-2274. [PMID: 30698431 DOI: 10.1021/acs.inorgchem.8b03568] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The bis(2-pyridylthio)methanidopalladium(II) pincer complex (1), containing a Pd-C bond, was obtained from the reaction of bis(2-pyridylthio)methane (H2L) with palladium(II) acetate in toluene under reflux. When palladium(II) trifluoroacetate was used, H2L reacted to generate the tetrakis(pyridine-2-thiol)palladium(II) complex (2). Complex 2 was converted to a heterobimetallic palladium(II)-iron(II) paddlewheel complex (3) upon treatment with iron(II) triflate in the presence of a base in acetonitrile at room temperature.
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Affiliation(s)
- Partha Halder
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Daniel J SantaLucia
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - Sungho V Park
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
| | - John F Berry
- Department of Chemistry , University of Wisconsin-Madison , 1101 University Avenue , Madison , Wisconsin 53706 , United States
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Mohammadi H, Shaterian HR. γ-Fe2O3@SiO2-γ-aminobutyric acid as a novel superparamagnetic nanocatalyst promoted green synthesis of chromeno[4,3,2-de][1,6]naphthyridine derivatives. MONATSHEFTE FUR CHEMIE 2018. [DOI: 10.1007/s00706-018-2317-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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17
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Ringenberg MR. Beyond Common Metal-Metal Bonds, κ 3 -Bis(donor)ferrocenyl→Transition-Metal Interactions. Chemistry 2018; 25:2396-2406. [PMID: 30238642 DOI: 10.1002/chem.201803150] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/24/2018] [Indexed: 12/22/2022]
Abstract
Ligands with 1,1'-bis(donor)ferrocene motif are capable of a wide range of binding modes, including the trans chelation mode in which there is a Fe-M interaction (κ3 -D,Fe,D), in the form of a dative Fe→TM bond (TM=transition metal). This Minireview will explore the nature of this Fe-TM interaction thorough select examples as well as how to characterize a Fe→TM dative bond using physical, computational, and spectroscopic techniques.
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Affiliation(s)
- Mark R Ringenberg
- Institute for Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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18
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Dai R, Lai A, Alexandrova AN, Diaconescu PL. Geometry Change in a Series of Zirconium Compounds during Lactide Ring-Opening Polymerization. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00620] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Ruxi Dai
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Amy Lai
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Anastassia N. Alexandrova
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Paula L. Diaconescu
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
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Exploring Oxidation State-Dependent Selectivity in Polymerization of Cyclic Esters and Carbonates with Zinc(II) Complexes. iScience 2018; 7:120-131. [PMID: 30267674 PMCID: PMC6153418 DOI: 10.1016/j.isci.2018.08.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/21/2018] [Accepted: 08/21/2018] [Indexed: 11/24/2022] Open
Abstract
Neutral zinc alkoxide complexes show high activity toward the ring-opening polymerization of cyclic esters and carbonates, to generate biodegradable plastics applicable in several areas. Herein, we use a ferrocene-chelating heteroscorpionate complex in redox-switchable polymerization reactions, and we show that it is a moderately active catalyst for the ring-opening polymerization of L-lactide, ɛ-caprolactone, trimethylene carbonate, and δ-valerolactone. Uniquely for this type of catalyst, the oxidized complex has a similar polymerization activity as the corresponding reduced compound, but displays significantly different rates of reaction in the case of trimethylene carbonate and δ-valerolactone. Investigations of the oxidized compound suggest the presence of an organic radical rather than an Fe(III) complex. Electronic structure and density functional theory (DFT) calculations were performed to support the proposed electronic states of the catalytic complex and to help explain the observed reactivity differences. The catalyst was also compared with a monomeric phenoxide complex to show the influence of the phosphine-zinc interaction on catalytic properties. Dimeric and monomeric zinc heteroscorpionate species were prepared Monomeric zinc complex gives irreversible chemical redox and is inactive toward ROP Dimeric zinc complex gives reversible chemical redox and is inactive toward ROP Oxidation of the zinc benzoxide species occurs at the phosphine moiety
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