Carborane: Dedicated to the Work of Professor Alan Welch

This Special Issue on carboranes is dedicated to Prof. Alan Welch on the occasion of his retirement and his outstanding contributions to the field of carborane chemistry. Polyhedral carboranes lie at the interface of organic and inorganic chemistry. One of their most attractive and important features is the variety and beauty of their chemical structures. They have found applications as diverse as catalysis, in Boron Neutron Capture Therapy, as liquid crystals and as semiconductors. This Special Issue illustrates the very comprehensive world of heteroborane chemistry, from liquid crystals to BNCT agents, di-halogen bonding to quantum chemical calculations of tetrel complexes of the carbonium ylide CB11H11, nickellacarboranes as potential acid–base sensors to revealing how the selective formations of metallacarborane diastereomers can arise and metallacarboranes as function as radical cation salts with dielectric or semiconductor properties

Boron in Catalysis and Materials Chemistry: A Themed Issue in Honor of Professor Todd B. Marder on the Occasion of His 65th Birthday

Boron, a metalloid with rich chemistry, continues to offer a diverse platform in designing novel catalysts and materials for applications in a variety of areas. This book, while celebrating Professor Todd Marder’s contributions to boron chemistry, on the occasion of his 65th birthday in November 2020, highlights and brings into focus some of the important discoveries in this field, through state-of-the-art reviews and research article

Synthesis and structural characterization of half- and full-sandwich group 4 metallacarboranes.

Kwong Wai-chuen.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 98-102).Abstracts in English and Chinese.Acknowledgement --- p.IAbstract (in English) --- p.IIAbstract (in Chinese) --- p.IIIAbbreviation --- p.VList of Compounds --- p.VIContents --- p.VIIChapter Chapter 1. --- IntroductionChapter 1.1 --- Metallacarboranes of the C2B4 Systems --- p.1Chapter 1.1.1 --- Group 1 Metallacarboranes of the C2B4 Systems --- p.3Chapter 1.1.2 --- Group 4 Metallacarboranes of the C2B4 Systems --- p.6Chapter 1.2 --- Group 4 Metallacarboranes of the C2B9 Systems --- p.17Chapter 1.3 --- Group 4 Metallacarboranes of the C2B10 Systems --- p.35Chapter 1.4 --- Applications of Group 4 Metallacarboranes --- p.44Chapter 1.5 --- Research Objectives --- p.47Chapter Chapter 2. --- Synthesis and Structural Characterization of Group4 Metallacarboranes of the C2B9 SystemsChapter 2.1 --- Synthesis and Structural Characterization of {{466}4:η2-[(C6H5CH2)2C2B9H9]2ZrCl(THF)} {Na(THF)3} --- p.48Chapter 2.2 --- Synthesis and Structural Characterization of [η4:η2- {(C6H5CH2)2C2B9H9} 2ZrCl(THF)] [Li(THF)4] --- p.54Chapter 2.3 --- Synthesis and Structural Characterization of ZrCl[N(SiMe3)2]3 --- p.57Chapter 2.4 --- "Synthesis and Structural Characterization of η2-(C6H5CH2)2C2B9H9]M(NEt2)2(NHEt2HCH2Cl2) (M = Ti, Zr)" --- p.62Chapter 2.5 --- "Synthesis and Structural Characterization of [μ-{ o-C6H4(CH2)2 }C2B9H9]2M(THF)2 (M = Zr, Hf)" --- p.68Chapter 2.6 --- Conclusion --- p.71Chapter Chapter 3. --- Synthesis and Structural Characterization of Group4 Metallacarboranes of the C2B10 SystemsChapter 3.1 --- "Synthesis and Structural Characterization of {{471}-l,，2-(o-C6H4(CH2)2)- 1,2-C2B 10H10]2Zr} {Na(THF)3}2 and {[μ-l，2-(o-C6H4(CH2)2)-l,2- C2B10H10]2ZrCl2} {Na(THF)3}2(THF)" --- p.72Chapter 3.2 --- Conclusion --- p.78Chapter Chapter4. --- Summary --- p.79Chapter Chapter5. --- Experimental Section --- p.81References --- p.98AppendixChapter I. --- Crystal Data and Summary of Data Collection and Refinement --- p.103Chapter II. --- Atomic Coordinates and Thermal Parameters --- p.109Chapter III. --- Bond Distances and Angles --- p.11

Carbon-bridged cyclopentadienyl amido group 4 metal complexes : ligand tuning and olefin polymerization

De organometaalchemie en vooral die van overgangsmetalen en lanthaniden heeft zich in 40-50 jaar buitengewoon sterk ontwikkeld. Niet alleen werd een breed gebied van synthese en karakterisatie van nieuwe verbindingen en uitgebreid reactiviteitsonderzoek ontsloten maar ook werd de ontwikkeling van nieuwe methoden en inzichten in meer toepassingsgerichte gebieden zoals de organische synthese maar vooral de (homogene en heterogene) katalyse door de organometaalchemie sterk gestimuleerd. ... Zie: Samenvatting

Stereoselective Cationic Polymerization of Vinyl Ethers Through Asymmetric Ion-Pairing Catalysis

I. Background and IntroductionThe thermomechanical properties of macromolecules can be directly linked to their tacticity, the relative stereochemistry of repeat units. Herein, the importance of polymer tacticity and strategies for stereoselective polymer synthesis are described. A brief discussion on stereoselective coordination–insertion, coordination–addition, anionic, and cationic polymerization methodologies is included.II. Mechanistic Insight into Using a Chiral Lewis AcidWe recently demonstrated asymmetric ion pairing catalysis as an effective approach to achieve stereoselective cationic polymerization of vinyl ethers through the use of a chiral Lewis acid. Herein, we provide a deeper understanding of stereoselective ion-pairing polymerization through comprehensive experimental and computational studies. These findings demonstrate the importance of ligand deceleration effects for the identification of reaction conditions that enhance stereoselectivity.III. Substrate Scope and Copolymerization Using a Chiral Lewis AcidAn evaluation of monomer substrates with systematic variations in steric parameters and functional group identities established key structure−reactivity and structure—property relationships for stereoselective polymerization facilitated by our chiral Lewis acid. This methodology also allowed for successful stereoselective copolymerization, enabling the systematic tuning of both glass transition and melting temperature in copolymers derived from alkyl vinyl ethers. Collectively, these results highlight the diverse material properties and expanded chemical space that can be accessed by this method.IV. Catalyst and Monomer ChiralityCatalyst and monomer chirality were thoroughly probed in the cationic polymerization of vinyl ethers enabled by both our chiral Lewis acid system, as well as a novel single component Brønsted acid system based on an imidodiphosphormidate (IDPi) scaffold. In the context of investigating the axial chirality of both catalyst scaffolds, we found that using differing enantiomeric ratios of either catalyst did not result in a change to polymer tacticity. Subsequent studies expanding the monomer scope to include enantioenriched vinyl ethers were then performed, enabling the systematic studying of match-mismatch effects within a polymerization. V. Using Chiral Hydrogen Bond DonorsHerein, we report the targeted binding of triflate anions with chiral squaramides for the stereoselective cationic polymerization of vinyl ethers. Kinetic investigations reveal a ligand deceleration effect, while temperature dependent stereoselectivity analyses confirm the need for low reaction temperatures. Further, this work represents the first example of anion binding catalysis applied to cationic polymerization, thereby introducing a new mechanistic framework for the continued exploration of stereoselective polymerizations as a whole.Doctor of Philosoph

Design and synthesis of cyclometalated transition metal complexes as functional phosphorescent materials

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2012.Vita. Cataloged from PDF version of thesis.Includes bibliographical references.Cyclometalated Ir(III) and Pt(II) compounds are among the most promising phosphorescent emitters for various applications, such as organic light emitting diodes (OLEDs), chemical sensors and bioimaging labels. This family of complexes exhibits high thermal and photo-stability, excellent quantum efficiency, and relatively short lifetime. More importantly, their luminescent properties can be fully tunable by modifying the coordinating ligands. In this thesis, a series of 2-(1,2,3-triazol-4-yl)-pyridine derivatives, referred to as the "click" ligands, are used to build phosphorescent Ir(III) and Pt(II) compounds. The robust and tolerant nature of the copper mediated 1,3-dipolar cycloaddition reactions offers great flexibility in the molecular design. Chapter 1 and Chapter 2 focus on the synthesis of heteroleptic cyclometalated Ir (III) and Pt(II) complexes by utilizing the Cu(I) triazolide intermediates generated in "click" reactions as transmetalating reagents. Ligand synthesis and metalation can be achieved in one pot under mild reaction conditions. For the Ir(III) system, the "click" ligands show switchable coordination modes, between the C, N- and N, N-chelation. These ligands act as C, N, N-bridging units to form unique zwitterionic dinuclear complexes with two cyclometalated Pt(II) units. In Chapter 3, cyclometalated Pt(II) complexes with N, N-chelating "click" ligands are synthesized. Their aggregation-induced solid-state emission is highly responsive to environmental stimuli, such as solvents, heat and mechanical force. This family of compounds represents the first thermotropic Col(h) liquid crystals with only one sidechain. Furthermore, the combined liquid crystalline and mechanochromic properties make them attractive functional materials.by Shuang Liu.Ph.D

Design nanostruktur založených na klastrových sloučeninách bóru ve vodných roztocích

Náplní této disertační práce bylo studium roztokového chování klastrových sloučenin bóru a jejich interakce s polymery, s důrazem na pochopení zákonitostí vedoucích k tvorbě příslušných nano-struktur. Kromě polymerního systému obsahujícího o-karboran, byl výzkum zaměřen zejména na chování kobalt bis(dikarbollidového) aniontu (COSAN). Hlavní myšlenkou bylo pochopit některé dosud nejasné aspekty micelizace COSANu v souladu s dlouhodobými badatelskými plány v naší skupině. Z toho důvodu byla provedena detailní kalorimetrická studie, která umožnila kromě dalších termodynamických parametrů stanovit hodnotu agregačního čísla solí COSANu při koncentracích blízkých kritické micelární koncentrace (KMK), což je obtížně dostupné pomocí jiných experimentálních technik. Použití acetonitrilu jako příměsi ve vodném roztoku COSANu se ukázalo jako velmi účinný prostředek pro získání alespoň přibližné představy o vnitřní struktuře micel COSANu, což je z experimentálního hlediska jinak velmi obtížné. Z provedených fyzikálně chemických experimentů plyne, že C-H skupiny COSANu pravděpodobně směřují dovnitř nano-agregátů. Dále byla studována solubilizace COSANu v micelách s hydrofobním jádrem a polyelektrolytovou slupkou, kde byl použit COSAN jako modelové léčivo kombinující elektrostatický náboj s hydrofobním...Thesis The main objective of this thesis is the study of boron cluster compounds in solution, their interaction with polymers and the formation of nanostructures. Most of the work was focused around cobalt bis(dicarbollide) (COSAN) but the incorporation of carborane into polymers was also studied. The idea was to close the knowledge gap around the way COSAN aggregates and continue the line of the laboratory in leading this topic. Therefore, we performed in-depth analysis of isothermal titration calorimetry curves to determine the aggregation number at concentrations around the critical micellar concentration (CMC). Thus, the aggregation number obtained was an improvement over previous data obtained a much higher concentration. The use of acetonitrile as a cosolvent in the micellization process helped formulate a model describing how C-H bonds in the COSAN micelles are directed towards the inside of the micelle. Furthermore, COSAN was used as a model drug for loading nanocarriers composed of hydrophobic core and charged corona. The importance of this work relies on the creation of guidelines for drug loading into similar polymeric vectors in order to determine how the nanocarrier will be affected. With the help of coarse-grained simulations, we determined that changes in the hydrophobicity of the...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Synthesis and Characterization of Group-13-Bridged [1]- and [1.1]Metallacyclophanes

The synthesis and characterization of the first aluminum- and gallium-bridged [1]chromarenophanes, [1]vanadarenophanes and [1]molybdarenophanes are described; these compounds belong to a class of compounds referred to as [1]metallacyclophanes. [1]Metallacyclophanes are strained, ring-tilted complexes that have a propensity to undergo ring-opening polymerizations (ROPs). On the basis of using bulky, intramolecularly coordinating ligands, the [1]metallacyclophanes described within have been synthesized and characterized. By exploring known transition-metal catalyzed ROP methodologies, a serendipitous discovery has been made. The gallium-bridged [1]molybdarenophane undergoes ring-opening reactions catalyzed by sigma donors such as thf and triethylphospine or by pi donors such as 1,5-cyclooctadiene. Known transition-metal catalyzed ROP methodologies proved to be unsuccessful with the aluminum- and gallium-bridged [1]metallarenophanes, possibly due to steric overprotection. The synthesis and characterization of the first [1.1]metallarenophanes is described. By utilizing ligands with dimethylamine-donor functionalities, aluminum- and gallium-bridged unstrained [1.1]chromarenophanes and [1.1]molybdarenophanes have been isolated. Gallium-bridged [1.1]metallarenophanes have been determined to be Class II compounds through investigations by cyclic voltammetry. Aluminum-bridged [1.1]metallarenophanes can not be successfully characterized by electrochemical measurements because of their acute sensitivity towards oxygen and moisture. All isolated [1.1]metallarenophanes adopt anti conformations in the solid state. Several new reactive aluminum, gallium and indium and compounds have been prepared that incorporate bulky donor ligands. All new compounds have been characterized by NMR spectroscopy, X-ray crystallography, mass spectrometry and elemental analysis. When comparing solid-state structures of [1]metallarenophanes, some generalizations can be made. For a given [1]metallarenophane gallium-bridged compounds are always more tilted when compared to their respective aluminum-bridged compound for reasons that still remain unknown. If the bridging element is kept constant, the tilt angles are found to increase in the order of Mo > V > Cr for the [1]metallarenophanes, which can be attributed directly to their respective metallic radii

Diffusion of tin from TEC-8 conductive glass into mesoporous titanium dioxide in dye sensitized solar cells

The photoanode of a dye sensitized solar cell is typically a mesoporous titanium dioxide thin film adhered to a conductive glass plate. In the case of TEC-8 glass, an approximately 500 nm film of tin oxide provides the conductivity of this substrate. During the calcining step of photoanode fabrication, tin diffuses into the titanium dioxide layer. Scanning Electron Microscopy and Electron Dispersion Microscopy are used to analyze quantitatively the diffusion of tin through the photoanode. At temperatures (400 to 600 °C) and times (30 to 90 min) typically employed in the calcinations of titanium dioxide layers for dye sensitized solar cells, tin is observed to diffuse through several micrometers of the photoanode. The transport of tin is reasonably described using Fick\u27s Law of Diffusion through a semi-infinite medium with a fixed tin concentration at the interface. Numerical modeling allows for extraction of mass transport parameters that will be important in assessing the degree to which tin diffusion influences the performance of dye sensitized solar cells

Synthesis and Characterization of Novel Pincer Ligands and Triarylaminium Oxidants

Diarylamido-based tridentate pincer ligands have become an important archetype in transition-metal chemistry and their reactivity has been widely explored. The diarylamido backbone offers rigidity and can be easily tuned to change the steric and electronic properties of the ligand. Motivated by previous successes, efforts were made to expand the scope of pincer ligands developed within the Ozerov group, which historically have been limited to C2V symmetric ligands bearing either two phosphine donor arms or two imine donor arms. New ligands synthesized for this purpose include CS symmetric ligands PNP and PNN ligands. In an effort to categorize pincer ligands commonly employed in the Ozerov group we set out to compare the redox properties of the ligands and their donor ability towards a metal center. This was a two part endeavor where we (a) obtained cyclic voltammograms for (pincer)MCl compounds of Group 10 metals and (b) measured the IR stretching frequencies of (pincer)RhCO compounds. Our underlying assumptions were that the cyclic voltammograms report on how easy it is to oxidize the ligand (approximates the electron-richness of the ligand) and that the IR stretching frequencies give insight into the “electron-richness” of the metal center (a reflection on the basicity of the pincer ligand). The results of this study suggest that changes to the ligand framework directly affect the level of conjugation and in turn affect the redox potentials and the ν(CO) values in a nearly linear fashion. The more electron-rich a ligand is, (due to direct conjugation from donor substituents on the diarylamido-backbone and from the influence of the donor arms) the more readily it is oxidized and the stronger donor it becomes. Chemical oxidations have become a rising field of interest. Triarylaminium oxidants are advantageous since they boast modest oxidation potentials and generate chemically neutral amines upon reduction. Our goal was to expand the scope of triarylaminium oxidants bearing non-coordinating carborane anions. A series of oxidizing triarylaminium radical cations were synthesized and isolated as [NAr3]^+[CRB11Cl11]^− salts (R = H, CH3). These salts were prepared by treatment of a neutral amine, Me3SiX (X = OTf, Cl), and Na[CRB11Cl11] (R = H, CH3) with half an equivalent of PhI(OAc)2