A5051854568- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Organoboron and organosilicon chemistry
- Synthesis and characterization of novel inorganic/organometallic compounds
- Coordination Chemistry and Organometallics
- Organometallic Complex Synthesis and Catalysis
- Asymmetric Hydrogenation and Catalysis
- Catalytic Cross-Coupling Reactions
- Crystallography and molecular interactions
- Advanced NMR Techniques and Applications
- Organophosphorus compounds synthesis
- Advanced Synthetic Organic Chemistry
- Phosphorus compounds and reactions
- Chemical Synthesis and Analysis
- Boron Compounds in Chemistry
- N-Heterocyclic Carbenes in Organic and Inorganic Chemistry
- Advanced MRI Techniques and Applications
- Atomic and Subatomic Physics Research
- Lanthanide and Transition Metal Complexes
- Catalytic C–H Functionalization Methods
- Ferrocene Chemistry and Applications
- Ammonia Synthesis and Nitrogen Reduction
- Magnetism in coordination complexes
- Cyclopropane Reaction Mechanisms
- Electron Spin Resonance Studies
University of Edinburgh
2014-2024
Saarland University
2012-2018
Institute of General and Inorganic Chemistry
2018
Klinikum Saarbrücken
2018
University of York
2007-2014
Society for Cardiovascular Angiography and Interventions
2001
The sensitivity of both nuclear magnetic resonance spectroscopy and imaging is very low because the detected signal strength depends on small population difference between spin states even in high fields. Hyperpolarization methods can be used to increase this thereby enhance strength. This has been achieved previously by incorporating molecular singlet para-hydrogen into hydrogenation reaction products. We show here that a metal complex facilitate reversible interaction with suitable organic...
While the characterization of materials by NMR is hugely important in physical and biological sciences, it also plays a vital role medical imaging. This success all more impressive because inherently low sensitivity method. We establish here that [Ir(H)(2)(IMes)(py)(3)]Cl undergoes both pyridine (py) loss as well reductive elimination H(2). These reversible processes bring para-H(2) py into contact magnetically coupled environment, delivering an 8100-fold increase (1)H signal strength...
The cationic iridium complex [Ir(COD)(PCy3)(py)]BF4 (1) is shown to react with dihydrogen in the presence of pyridine (py) form dihydride fac,cis-[Ir(PCy3)(py)3(H)2]BF4 (2). Complex 2 undergoes rapid exchange two bound ligands which are trans hydride free pyridine; activation parameters for this process methanol ΔH⧧ = 97.4 ± 9 kJ mol−1 and ΔS⧧ 84 31 J K−1 mol−1. When parahydrogen employed as a source nuclear spin polarization, spontaneous magnetization transfer proceeds low magnetic field...
Abstract An aluminum‐catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL‐H or bench‐stable Et 3 Al⋅DABCO as catalyst and H‐Bpin both boron reagent stoichiometric source has been developed. Mechanistic studies revealed a unique mode reactivity in which reaction is proposed to proceed through hydroalumination σ‐bond metathesis between resultant alkenyl species HBpin, acts drive turnover catalytic cycle.
The aluminum-catalyzed hydroboration of alkenes with HBpin is reported using simple commercially available aluminum hydride precatalysts [LiAlH4 or sodium bis(2-methoxyethoxy)aluminum (Red-Al)]. Good substrate scope and functional group tolerance demonstrated for alkene hydroboration, the protocol was also applied to ketone, ester, nitrile groups, showing potential wider application. proposed proceed by hydroalumination, which generates an alkyl species that undergoes σ-bond metathesis drive...
We report on a strategy for using SABRE (signal amplification by reversible exchange) polarizing (1)H and (13)C nuclei of weakly interacting ligands which possess biologically relevant nonaromatic motifs. first demonstrate this via the polarization acetonitrile, Ir(IMes)(COD)Cl as catalyst precursor, confirm that route to hyperpolarization transfer is J-coupling network. extend work propionitrile, benzylnitrile, benzonitrile, trans-3-hexenedinitrile in order assess its generality. In NMR...
The cationic iridium complexes [Ir(COD)(PR3)2]BF4 (1a-c) (a, R = Ph; b, p-tolyl; c, p-C6H4−OMe) react with parahydrogen in the presence of pyridine to give trans, cis, cis-[Ir(PR3)2(py)2(H)2]+ (2a-c) and small amounts fac, cis-[Ir(PR3)(py)3(H)2]+ (3a-c), each which exhibit polarized hydride resonances due magnetic inequivalence associated resultant AA"XX" spin system when 15N-labeled is employed. ligands 2 are labile, exchanging slowly into free a rate constant 0.4 s−1 for 2a at 335 K...
SiSi activation: Reversible formation of a donor–acceptor complex between an N-heterocyclic carbene and cyclotrisilene with carbon-based substituents shifts the electron density double bond thus induces strong polarization, as shown by significantly pyramidal tricoordinate silicon atom.
Ir(COD)(NHC)Cl complexes provide significant insight into the catalytic processes underpinning SABRE hyperpolarization.
Hyperpolarization methods are used in NMR to overcome its inherent sensitivity problem. Herein, the biologically relevant target nicotinamide is polarized by hyperpolarization technique signal amplification reversible exchange. We illustrate how polarization transfer field, and concentrations of para hydrogen, polarization‐transfer‐catalyst substrate can be maximize exchange effectiveness reference first‐order spin system this target. The catalyst shown crucial process, first facilitating...
Abstract The reactivity of the 2‐phosphaethynolate anion (PCO − ) towards a cyclic trisilene (cSi 3 (Tip) 4 is reported. result net activation PC and SiSi multiple bonds precursors affording heteroatomic bicyclo[1.1.1]pentan‐2‐one analogue ([P(CO)Si ] ; 1 ). This reaction can be interpreted as formal addition phosphide carbonyl across double bond. Photolytic decarbonylation results in incorporation vertex into cyclotrisilene scaffold, yielding congener cyclobutene with considerable allylic...
Simple, commercially available borane adducts, H3B·THF and H3B·SMe2, have been used to catalyse the hydroboration of alkynes alkenes with pinacolborane give alkenyl alkyl boronic esters, respectively. Alkynes terminal underwent highly regioselective linear ester products. Good functional group tolerance was observed for substrates bearing ester, amine, ether halide substituents. This catalytic process shows comparable reactivity transition-metal-catalysed protocols.
Abstract Dialumenes are neutral Al I compounds with Al=Al multiple bonds. We report the isolation of an amidophosphine‐supported dialumene. Our X‐ray crystallographic, spectroscopic, and computational DFT analyses reveal a long extreme trans‐bent bond low dissociation energy order. In solution, dialumene can dissociate into monomeric species. Reactivity studies two modes reaction: as or aluminyl monomers.
Abstract The generation of heavier double‐bond systems without by‐ or side‐product formation is considerable importance for their application in synthesis. Peripheral functional groups such alkene homologues are promising this regard owing to inherent mobility. Depending on the steric demand N‐alkyl substituent R, reaction disilenide Ar 2 SiSi(Ar)Li (Ar=2,4,6‐ i Pr 3 C 6 H ) with ClP(NR either affords phosphinodisilene SiSi(Ar)P(NR (for R= Pr) P‐amino functionalized phosphasilenes (R...
An aluminum-catalyzed hydroboration of alkynes using either the commercially available aluminum hydride DIBAL-H or bench-stable Et3Al⋅DABCO as catalyst and H-Bpin both boron reagent stoichiometric source has been developed. Mechanistic studies revealed a unique mode reactivity in which reaction is proposed to proceed through hydroalumination σ-bond metathesis between resultant alkenyl species HBpin, acts drive turnover catalytic cycle.
We report the phospha-bora-Wittig reaction for direct preparation of phosphaalkenes from aldehydes, ketones, esters, or amides. The transient phosphaborene Mes*P═B–NR2 reacts with carbonyl compounds to form 1,2,3-phosphaboraoxetanes, analogues oxaphosphetane intermediates in classical Wittig reaction. 1,2,3-Phosphaboraoxetanes undergo thermal Lewis acid-promoted cycloreversion, yielding phosphaalkenes. Experimental and density functional theory studies reveal far-reaching similarities...
SiSi-Aktivierung: Die reversible Bildung eines Donor-Akzeptor-Komplexes zwischen einem N-heterocyclischen Carben und Cyclotrisilen mit C-Substituenten verschiebt die Elektronendichte der Doppelbindung induziert somit eine starke Polarisierung, wie durch das signifikant pyramidale dreifachkoordinierte Siliciumatom verdeutlicht wird.
Spontaneous reaction of carbon monoxide with cyclotrisilenes has been observed. Depending on the substitution pattern, initial product carbonylation either dimerizes or can be trapped to yield highly functionalized cyclic silenes. As a service our authors and readers, this journal provides supporting information supplied by authors. Such materials are peer reviewed may re-organized for online delivery, but not copy-edited typeset. Technical support issues arising from (other than missing...
Abstract Wir berichten über die Reaktivität des 2‐Phosphaethinolat‐Anions (PCO − ) gegenüber einem cyclischen Trisilen (cSi 3 (Tip) 4 ), in einer Nettoaktivierung der P‐C‐ und Si‐Si‐Mehrfachbindungen Vorstufen resultiert so das heteroatomare Bicyclo[1.1.1]pentan‐2‐on‐Analogon [P(CO)Si ] ( 1 erzeugt. Diese Reaktion kann als formale Addition eines Phosphids Carbonyls Si‐Si‐Doppelbindung interpretiert werden. Photolytische Decarbonylierung von im Einbau Phosphideinheit Cyclotrisilengerüst...
Formal exchange of C=C units with isoelectronic B=N or B=P can provide access to molecules unique electronic chemical properties. Herein, we report the simple solution-phase generation highly reactive phosphaborenes, RP=BR, and demonstrate their use for introduction P=B into organic systems. Ring opening a P-B-containing cyclobutene isostere provided 1,4-boraphosphabutadiene systems conjugated main-group multiple bonds.
The equilibrium between disilenes (R2 Si=SiR2 ) and their silylsilylene (R3 Si-SiR) isomers has previously been inferred but not directly observed, except in the case of parent system H2 Si=SiH2 . Here, we report a new method to prepare base-coordinated with hydride substituents. By varying bulk coordinating base other silicon substituents, have able control rearrangement disilene adducts tautomers. Remarkably, 1,2 migration trimethylsilyl group is preferred over hydrogen migration. A DFT...
Abstract Oxidative addition and reductive elimination are defining reactions of transition‐metal organometallic chemistry. In main‐group chemistry, oxidative is now well‐established but not yet general in the same way. Herein, we report dihydrodialanes supported by amidophosphine ligands. The ligand serves as a stereochemical reporter for reversible elimination/oxidative chemistry involving Al I III intermediates.
The reaction of cyclotrisilenes 1 with equiv alkyl and aryl isocyanides at 25 °C affords the four-membered trisilacyclobutenes 2 an exocyclic imine functionality as major products formal insertion into one Si–Si single bonds 1. Minor quantities iminotrisilabicyclo[1.1.0]butanes 3 are obtained side products, formally resulting from [1 + 2] cycloaddition to double bond bicyclo[1.1.0]butanes become dominant lower temperatures may react additional isonitriles give diiminotrisilabicyclo[1.1.1]pentanes 4.
The first magnesium, copper and zinc disilenides were prepared via transmetallation reactions of a lithium disilenide structurally characterised. derivatives show red-shifted UV/vis absorptions due to admixture metal d-orbitals the highest occupied molecular orbital.