Article
Chemistry, Physical
Jonathan E. Chellali, Alexander K. Alverson, Jerome R. Robinson
Summary: This study reports a new class of Zn catalysts that exhibit high activity and stability in the ring-opening polymerization of lactide. Mechanistic studies revealed a quantitative structure-function relationship between the steric profile of the catalyst's reaction site and its activity, providing important insights for the design of homogeneous catalysts.
Article
Polymer Science
Yi Wan, Yun Bai, Hai Xu, Jianghua He, Yuetao Zhang
Summary: The study successfully synthesized five chiral binuclear aluminum methyl complexes, which catalyze the ring-opening polymerization of rac-lactide in a controlled manner and produce polymers with high isoselectivity. The kinetic studies show a first-order dependence on monomer concentration, supporting an enantiomorphic site control mechanism for the catalysts. This strategy can also be applied to other lactones for ring-opening polymerization.
MACROMOLECULAR RAPID COMMUNICATIONS
(2021)
Article
Polymer Science
Salvatore Impemba, Gabriele Manca, Irene Tozio, Stefano Milione
Summary: In this study, new zinc catalysts were developed using thioether-amide ligands for the ring-opening polymerization of cyclic esters. Experimental and theoretical studies provided insights into the parameters that influence catalytic activity. The catalysts exhibited high activity in the polymerization of rac-beta-butyrolactone and showed agreement with expected results in terms of molecular weight and polydispersity index.
Article
Polymer Science
Fangping Ren, Xinlei Li, Ji Xian, Xinning Han, Luya Cao, Xiaobo Pan, Jincai Wu
Summary: This study reports three bench-stable potassium phenolates as isoselective catalysts for the ring-opening polymerization of lactides. These catalysts exhibit high activity under moisture conditions and allow for controllable polymerization reactions.
JOURNAL OF POLYMER SCIENCE
(2022)
Article
Chemistry, Physical
Federica Tufano, Federica Santulli, Fabia Grisi, Marina Lamberti
Summary: Two zinc complexes with NHC ligands were synthesized and studied for their behavior in the Ring-Opening Polymerization of lactides, showing efficiency as initiators with molecular weights dependent on cocatalysts. Microstructural analysis revealed enriched heterotactic PLA, with kinetic parameters compared between different conditions and reactions showing pseudo-first-order dependence on monomer concentration. Reactivity studies aimed to uncover the active species in polymerization processes with different catalytic systems, including zinc complexes alone or in combination with neutral or ionic cocatalysts.
Article
Polymer Science
Na Liu, Doudou Liu, Bo Liu, Hao Zhang, Dongmei Cui
Summary: The reaction of heteroscorpionated ligands with homoleptic calcium amide resulted in the formation of new zwitterionic calcium complexes. These complexes were characterized and tested for their controlled polymerization of rac-lactide, showing linear increase in molecular weights with monomer-to-catalyst ratio. Surprisingly, at different temperatures, the complexes produced polylactides with different stereochemistries.
Review
Chemistry, Multidisciplinary
Mathieu J. -L. Tschan, Regis M. Gauvin, Christophe M. Thomas
Summary: This review summarizes the recent developments in biodegradable polymeric materials over the past decade, with a focus on the stereoselective ring-opening polymerization of cyclic esters and the emergence of metal-free stereocontrolled ROP technology. The study emphasizes the synthesis of new stereoselective polymerization catalysts and chiral monomers, while also highlighting the quantification and mechanisms of stereocontrol.
CHEMICAL SOCIETY REVIEWS
(2021)
Article
Polymer Science
Zhedong Li, Shiwei Duan, Na Zhao, Zhibo Li
Summary: In this study, two bulky phenyl diphosphazene bases, p-PDPB and m-PDPB, were synthesized and used in combination with ureas and squaramides as hydrogen-bond donors to mediate stereocontrolled ring opening polymerization (ROP) of lactide. The phenyl diphosphazene based/urea binary catalytic system successfully synthesized semicrystalline PLAs with narrow dispersity and high tacticity (P-m up to 0.84) in a well-controlled manner. Structural analysis confirmed the linear structure and high end-group fidelity of the resulting polymers, and MALDI-TOF MS analysis indicated the good controllability of the binary catalytic system with minimal transesterification.
JOURNAL OF POLYMER SCIENCE
(2023)
Article
Chemistry, Inorganic & Nuclear
Xiaowei Xu, Han Lu, Gen Luo, Xiaohui Kang, Yi Luo
Summary: The origin of opposite reactivity in the ring-opening polymerizations of lactide (LA) and cyclohexene oxide (CHO) catalyzed by redox-switchable bis(imino)pyridine iron complexes has been computationally elucidated. Larger geometrical deformation leads to lower activity of the oxidized form (Fe-ox) of the iron catalyst toward LA polymerization compared to the reduced analogue (Fe-red), while the higher activity of Fe-ox toward CHO polymerization is attributed to stronger interaction with CHO moieties due to its higher electrophilicity. This theoretical understanding has led to the computational modeling of various Fe-ox analogues with modified substituents to increase their electrophilicity and lower energy barriers in CHO enchainment.
INORGANIC CHEMISTRY FRONTIERS
(2021)
Article
Chemistry, Inorganic & Nuclear
Hong Zhang, Xiaoyun Geng, Ziqiang Li, Ying Peng, Lijuan Wang, Pengjiao Chen
Summary: A series of N-alkyl-beta-ketoiminate monozinc complexes were synthesized and characterized. The structures of these complexes were determined by single-crystal X-ray diffraction, revealing a distorted tetrahedral geometry around the zinc center. These bis(beta-ketoiminate) zinc complexes exhibited high activity towards the ring-opening polymerization of rac-lactide in the absence of alcohol.
INORGANICA CHIMICA ACTA
(2023)
Article
Chemistry, Multidisciplinary
Chunping Feng, Debao Mu, Xuehua Zhu, Yaorong Wang, Dan Yuan, Yingming Yao
Summary: This study investigated the reactivity of benzoxazine functionalized amine bridged bis(phenol)s with rare earth metal complexes and found that the substituents of the ligand and the rare earth metals had influences on the reaction outcomes. Additionally, these compounds showed high efficiency in catalyzing the ring-opening polymerization of rac-lactide.
CHINESE JOURNAL OF CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Jayeeta Bhattacharjee, Alok Sarkar, Tarun K. Panda
Summary: This review highlights the progress of alkali metal-based catalysis for the ring opening polymerization of rac-lactide, critically assesses futuristic research, spotlights major developments achieved in the past few years, and provides an overview of the challenges and opportunities.
CURRENT OPINION IN GREEN AND SUSTAINABLE CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Alina Hermann, Tabea Becker, Martin A. Schaefer, Alexander Hoffmann, Sonja Herres-Pawlis
Summary: The study synthesized two new guanidine hydroquinoline ligands as the basis for six new zinc guanidine complexes, two of which showed high activity in lactide polymerization. The research demonstrated the excellent ability of zinc guanidine complexes to catalyze both polymerization and depolymerization.
Article
Chemistry, Multidisciplinary
Jiang Dai, Wei Xiong, Dong-Yu Li, Zhongzheng Cai, Jian-Bo Zhu
Summary: By combining two stereogenic elements, we have successfully designed a series of bifunctional thiourea-based organocatalysts, which enable stereoselective polymerization of lactide to produce iso-enriched polylactide.
CHEMICAL COMMUNICATIONS
(2023)
Article
Polymer Science
Hans R. Kricheldorf, Steffen M. Weidner, Felix Scheliga
Summary: Alcohol-initiated ring-opening polymerizations of L-Lactide were conducted, and it was found that caprylate exhibited the highest catalytic activity among the three catalysts tested. Increasing the LA/Cat ratio resulted in higher fractions of cyclic polymers.
JOURNAL OF POLYMER SCIENCE
(2022)
Article
Chemistry, Inorganic & Nuclear
William J. M. Blackaby, Katie L. M. Harriman, Samuel M. Greer, Andrea Folli, Stephen Hill, Vera Krewald, Mary F. Mahon, Damien M. Murphy, Muralee Murugesu, Emma Richards, Elizaveta Suturina, Michael K. Whittlesey
Summary: A new series of homoleptic Ni(I) bis-N-heterocyclic carbene complexes with different torsion angles between the ligands have been reported. The complexes exhibit a strongly anisotropic g-tensor and the first excited state energy ranges from 270 to 650 cm(-1). The magnetic relaxation is dominated by Raman and direct processes, and the temperature dependence of the relaxation does not correlate with the torsion angle.
INORGANIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Thomas G. Linford-Wood, Mary F. Mahon, Matthew N. Grayson, Ruth L. Webster
Summary: This paper presents a synthetic study into the catalytic hydrogen/deuterium exchange of 1 degrees silanes, 2 degrees silanes, and 3 degrees siloxanes facilitated by iron-beta-diketiminato complexes (1a and 1b). Near-complete H/D exchange is observed for various aryl- and alkyl-containing hydro-silanes and hydrosiloxanes. The reaction tolerates alternative hydride source pinacolborane (HBpin) with quantitative H/D exchange. A synthetic and density functional theory (DFT) investigation suggests that a monomeric iron-deuteride is responsible for the H/D exchange.
Article
Chemistry, Multidisciplinary
Kyle G. Pearce, Chiara Dinoi, Michael S. Hill, Mary F. Mahon, Laurent Maron, Ryan S. Schwamm, Andrew S. S. Wilson
Summary: The synthesis and catalytic properties of hydrocarbon-soluble beta-diketiminato phenylcalcium derivatives are discussed in this article. The compounds display different modes of Ca-mu(2)-Ph-Ca bridging and can selectively and uncatalyzedly form biaryls when reacted with aryl bromides.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Lia Sotorrios, Fedor M. Miloserdov, Anne-Frederique Pecharman, John P. Lowe, Stuart A. Macgregor, Mary F. Mahon, Michael K. Whittlesey
Summary: The syntheses, reactivity, and electronic structure analyses of [Ru(PPh3)(2)(ZnMe)(4)H-2] and [Ru(PPh3)(2)(ZnPh)(4)H-2] are reported. [Ru(PPh3)(2)(ZnMe)(4)H-2] exhibits an 8-coordinate Ru center with axial phosphines and a symmetrical (2 : 2) arrangement of ZnMe ligands in the equatorial plane. The ZnMe ligands in [Ru(PPh3)(2)(ZnMe)(4)H-2] undergo facile, sequential exchange with ZnPh2 to give [Ru(PPh3)(2)(ZnPh)(4)H-2], which shows a 3 : 1 arrangement of ZnPh ligands. Mechanisms for ZnMe/ZnPh exchange and isomerization are proposed using DFT calculations, and the relationships of these {Ru(ZnR)(4)H-2} species to isoelectronic Group 8 transition metal polyhydrides and related Schlenk equilibria in the Negishi reaction are discussed.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Adam N. Barrett, Martin Diefenbach, Mary F. Mahon, Vera Krewald, Ruth L. Webster
Summary: In this study, gram-scale quantities of 2,4,6-tris(triphenylmethyl)-Dewar-1,3,5-triphosphabenzene were synthesized using an alkyne cyclotrimerization regime. It was found that this compound can undergo rearrangement and phosphorus migration reactions to form ring-contracted species. Additionally, novel crystallographically characterized products of other transformations were reported.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Han-Ying Liu, Samuel E. Neale, Michael S. Hill, Mary F. Mahon, Claire L. McMullin, Emma Richards
Summary: Ionic compounds containing sodium cations are known for their stability and resistance to redox reactivity. However, when treated with non-reducible organic bases, a low oxidation state {Mg2Na2} species undergoes selective extrusion of sodium metal and oxidation of the Mg-I centers. Quantum chemical studies indicate that intramolecular electron transfer is facilitated by the molecular orbitals of the {Mg2Na2} ensemble.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Laura E. English, Thomas M. Horsley Downie, Catherine L. Lyall, Mary F. Mahon, Claire L. McMullin, Samuel E. Neale, Carla M. Saunders, David J. Liptrot
Summary: The (IPr)CuOtBu catalysed reduction of 11 aryl and alkyl isocyanates with pinacolborane resulted in the formation of boraformamides, pinBN(R)C(O)H, in most cases. Overreduction was observed only for electron poor aryl isocyanates (4-NC-C6H4NCO, 4-F3C-C6H4NCO, 3-O2N-C6H4NCO). Computational analysis revealed that the stability of [(IPr)CuH](2), proposed as the catalyst resting state, influences selectivity and offers a potential solution to prevent overreduction in future work. In the case of iPrNCO, the formation of [(IPr)CuH](2) prevents overreduction kinetically. However, for 4-NC-C6H4NCO, the barrier height for the first step of overreduction is much lower, resulting in unselective reduction.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Kyle G. G. Pearce, Michael S. S. Hill, Mary F. F. Mahon
Summary: Reaction of BeCl2 with dilithium diamide yields the dimeric chloroberyllate, leading to the formation of a 2-coordinate beryllium amide. Reduction of the beryllium amide using lithium or sodium in benzene produces relevant organoberyllate products, likely through transient Be(i) radicals.
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Inorganic & Nuclear
Henry T. W. Shere, Michael S. Hill, Samuel E. Neale, Mary F. Mahon, Claire L. McMullin, Andrew S. S. Wilson
Summary: This article investigates the contrasting reactivities of molecular beta-diketiminato (BDI) calcium hydride and n-hexyl derivatives towards bis(pinacolato)diboron (B(2)pin(2)). The study finds that the dimeric calcium hydride forms an unusual diborane(6) dianion, while the initially dimeric organocalcium reagent converts to a calcium diboranate monomer. Attempts to induce heterolysis of the B-B bond in the calcium diboranate monomer were unsuccessful, resulting in either dismutation or the generation of N-donor adduct derivatives. These different reactivities can be explained by density functional theory (DFT) calculations, which attribute them to the larger radius and lower steric congestion of the third-row group 2 cation.
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE
(2023)
Article
Chemistry, Inorganic & Nuclear
Anne-Frederique M. Pecharman, Erika M. Roberts, Fedor M. Miloserdov, Victor Varela-Izquierdo, Mary F. Mahon, Michael K. Whittlesey
Summary: The addition of excess ZnMe2 to a mixture of [Ru(PPh3)(3)HCl] and IMes resulted in the formation of a bis-cyclometallated complex [Ru(IMes)(PPh3)(2)] 2 and a mono-cyclometallated Ru-Zn heterobimetallic complex [Ru(IMes)'(PPh3)(2)(ZnMe)] 3. Further reactions of these complexes with H-2, PhSiH3, pinacolborane, and CO were investigated. Compounds 1, 4, 5, and 6 were synthesized and structurally characterized.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2023)
Article
Chemistry, Physical
Antoine Buchard, Christopher J. Chuck, Matthew G. Davidson, Gerrit Gobius du Sart, Matthew D. Jones, Strachan N. McCormick, Andrew D. Russell
Summary: We have developed a zirconium-based catalytic system for the industrial production of high-molecular-weight poly(lactic acid) (PLA). We were able to prepare high-molecular-weight PLA under both laboratory and industrial conditions, with the catalyst activity comparable to that of conventional tin catalysts.
Article
Chemistry, Inorganic & Nuclear
Anne-Frederique M. Pecharman, Rosalyn L. Falconer, Esme Owen, Michael J. Cowley, John P. Lowe, Claire L. McMullin, Mary F. Mahon, Michael K. Whittlesey
Summary: Treatment of [Ru(L)(PPh3)2(CO)H2] (L = PPh3, IMes) with an N-mesityl amidophosphine aluminium dihydride complex (Al(P-N)H2) gives [Ru(PPh3)2(CO)H3{Al(P-N)H}] (2) and [Ru(IMes)(PPh3)(CO)H3{Al(P-N)H}] (4), which are present in solution as mixtures of diastereomers. Crystal structure determinations and density functional theory (DFT) calculations suggest both 2 and 4 can be formulated as [Ru(L)(PPh3)(CO)H3][Al(P-N)H] complexes with bridging hydride ligands.
Article
Chemistry, Inorganic & Nuclear
Henry T. W. Shere, Michael S. Hill, Mary F. Mahon
Summary: This contribution describes the formation of homonuclear sigma bonding between boron mediated by alkaline earth metals. The reaction between alkaline earth bis-(trimethylsilyl)amides and bis(pinacolato)diboron resulted in the formation of group 2 silazide diborane adducts. Further reaction with bis(pinacolato)diboron led to the formation of bis-triboranate derivatives. These complexes provide rare examples of catena-boron species with propagated B-B bonds beyond the common diboranes.
Article
Chemistry, Multidisciplinary
Han-Ying Liu, Samuel E. Neale, Michael S. Hill, Mary F. Mahon, Claire L. McMullin, Benjamin L. Morrison
Summary: [{SiNDipp}MgNa](2) reacts directly with H-2 to form a heterobimetallic hydride. Computational density functional theory (DFT) studies suggest that this reactivity is initiated by orbitally-constrained sigma(Mg-Mg)-> sigma*(H-H) and sigma(H-H) -> n*(Na(3s)) interactions between the frontier MOs of both H-2 and the tetrametallic core of [{SiNDipp}MgNa](2).
CHEMICAL COMMUNICATIONS
(2023)
Article
Chemistry, Multidisciplinary
Han-Ying Liu, Samuel E. Neale, Michael S. Hill, Mary F. Mahon, Claire L. McMullin
Summary: The copper(i) alumanyl derivative reacts with up to three equivalents of various terminal alkynes, resulting in the sequential formation of cuprous (hydrido)(alkynyl)aluminate, (alkenyl)(alkynyl)aluminate, and bis(alkynyl)aluminate derivatives. The alkene liberation process in the latter step is a unique case of alkyne transfer semi-hydrogenation.
