
Wolfgang A. HerrmannTechnical University of Munich | TUM · Section of Inorganic Chemistry
Wolfgang A. Herrmann
PhD
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Publications (925)
The synthesis and characterization of two water-soluble bis-N-heterocyclic carbene (NHC) complexes of rhodium and iridium is presented. Both compounds are active in H2 generation from formic acid and in hydrogenation of bicarbonate to formate. The rhodium derivative is most active in both reactions, reaching a TOF of 39 000 h(-1) and a TON of 449 0...
A series of complexes of the formula [Pt(dvtms)(ImPy–R)] (dvtms = 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, ImPy–R = 2-R-imidazo[1,5-a]pyridine-3-ylidene; R = 4-cyanophenyl (4a), 4-trifluoromethylphenyl (4b), phenyl (4c), 4-methoxyphenyl (4d), mesityl (4e), pentafluorophenyl (4f), tert-butyl (4g)) are presented. These compounds are synthesized fro...
Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more...
Hydrosilylation of C–C multiple bonds is one of the most important applications of homogeneous catalysis in industry. The reaction is characterized by its atom-efficiency, broad substrate scope, and widespread application. To date, industry still relies on highly active platinum-based systems that were developed over half a century ago. Despite the...
The hydrosilylation of allyl compounds is very important for the industrial production of γ-substituted propylsilanes; however, it is also a process known to suffer from either substantial selectivity issues or short catalyst lifetimes. While there are reports on the platinum-catalyzed variant, this study is the first comprehensive work on the more...
Ever since the isolation of the first free N-heterocyclic carbene more than 20 years ago, this ligand class has become essential in modern chemistry. This development is decisively owed to the stability of the metal-carbon bond, the smooth fine-tuning of ligand properties, and the facile synthetic access tosuch complexes. Acting as steering ligands...
Amino-functionalised metal-organic frameworks UiO-66 and -67 were post-synthetically modified with salicylaldehyde. A molybdenum complex was immobilised on the resulting materials. They were characterised by 13C-MAS-NMR and PXRD to confirm immobilisation and stability. The immobilised complex is an active and reusable catalyst for olefin epoxidatio...
In recent years, the use of copper N-heterocyclic carbene (NHC) complexes has expanded to fields besides catalysis, namely medicinal chemistry and luminescence applications. In the latter case, multinuclear copper NHC compounds have attracted interest, however, the number of these complexes in the literature is still quite limited. Bis[μ-1,3-bis...
Ever since the isolation of the first free N-heterocyclic carbene more than 20 years ago, this ligand class has become essential in modern chemistry. This development is decisively owed to the stability of the metal-carbon bond, the smooth fine-tuning of ligand properties, and the facile synthetic access to such complexes. Acting as steering ligand...
The synthesis of cyclic carbonates through coupling of carbon dioxide with epoxides is 100 % atom economical and is already performed on an industrial scale. Its impact regarding the use of carbon dioxide as a renewable carbon source is expected to grow significantly in the near future, so that the development of efficient catalysts is of high inte...
The direct synthesis of the first μ2-η2,η2- allyl-bridged diiridium complex ([2]+), bearing the uncommon counterion [IrCl2(COD)]− ([3]−), is described. Both bridging moieties in [2]+, namely, allyl and acetate, are introduced in a single reaction step from [{IrCl(COD)}2] (1) and allyl acetate. A combination of X-ray crystallography and density func...
The synthesis of five new silver(I) NHC complexes, bearing alkylenebimpy ligands with bridge lengths ranging from ethylene to hexylene is described. Their solid-state structures exhibit an unforeseen variety, including infinite strands of Ag3 units within a helically wound ligand environment. The very first infinite chain of almost linear Ag3 units...
A series of imidazolium perrhenates with different substituents at the imidazolium ring were synthesised and characterised, including single crystal X-ray diffraction. The effect of the substitution pattern on the state of aggregation of the compounds, the charge delocalisation and the ion pairing interaction via hydrogen bonds was studied. Particu...
Organorhenium complexes are attracting interest because of their possible uses as deoxygenation catalysts in the refinement of lignocellulosic biomass such as lignin, carbohydrates, and sugar alcohols in the homogeneous phase. Furthermore, organorhenium compounds are known for their promising catalytic applications in the olefination of aldehydes,...
Hydroxymethyl-functionalized methylene-bridged dinuclear N-heterocyclic bis(NHC) complexes with Ag(I) (2), Cu(I) (3) and Au(I) (4) have been synthesized and characterized by spectroscopic methods and X-ray diffraction studies. Depending on the metal employed, different isomers are formed. The structural properties and differences of all three new c...
Organic-phase supramolecular ion pair (SIP) host–guest assemblies of perrhenate anions (ReO4−) with ammonium amide receptor cations are reported. These compounds act as catalysts for the epoxidation of alkenes by aqueous hydrogen peroxide under biphasic conditions and can be recycled several times with no loss in activity.
A series of salts containing the weakly coordinating cations (WCC) 1-butyl-3-methylimidazolium ([Bmim]+), 1-butyl-2,3-dimethylimidazolium ([Bdmim]+), 1-dodecyl-3-methylimidazolium ([C12mim]+), tetrabutylphosphonium ([PBu4]+), tributyltetradecylphosphonium ([P 4,4,4,14 ] +), tetrabutylammonium ([NBu4]+), and 1,1,3,3-tetramethylguanidium ([TMG]+) and...
Hydroxy-functionalized mono- and bisimidazolium bromides were synthesized and applied as catalysts for the cycloaddition of CO2 and epoxides to cyclic carbonates. A catalyst screening showed the influence of the number of protic hydrogen atoms at the cation for the activation of epoxides. The most active catalyst operates at very mild reaction cond...
Novel iridium(I) complexes bearing N-donor-functionalized N-heterocyclic carbene ligands were synthesized. Although hemilabile coordination of the attached donor is considered beneficial in catalysis, no detailed study of this phenomenon in these systems is available to date. The present report provides insight into the hemilabile bonding propertie...
A range of imidazolium- and pyridinium-substituted η3-cycloheptatrienide-Pd complexes was synthesized by nucleophilic attack of different N-donors on cycloheptatrienylidene-Pd complexes. Their full characterization is reported along with DFT studies of their formation and special properties. The target compounds represent the first crystallographic...
The epoxidation of propene is performed in homogeneous phase using different molecular catalysts and H2O2 or tert-butyl hydroperoxide as oxidants. A comparison between molybdenum catalysts and methyltrioxorhenium (MTO) shows that the well known Re catalyst is the best among the examined catalysts.
This work reports on iron-catalysed hydroxylation of benzene and toluene using aqueous H2O2. While benzene is hydroxylated with a high selectivity to phenol, toluene is hydroxylated to cresols with a high selectivity for the ortho and para-position. An inverse KIE indicates the presence of a high valent Fe[double bond, length as m-dash]O species du...
A new immobilization mode for methylene-bridged bis(NHC) (NHC=N-heterocyclic carbene) ligand systems is presented, allowing fine-tuning of the steric and electronic properties of the bidentate ligand. For example, four hydroxymethyl-functionalized imidazolium salts (1 a–c and 2 a) and three bis(NHC) Pd complexes 3 a, 3 b, and 4 a are described. The...
A novel approach towards the synthesis of radiolabeled organometallic rhenium complexes is presented. We successfully synthesized and analyzed the first (188) Re-labeled N-heterocyclic biscarbene complex, trans-dioxobis(1,1'-methylene-bis(3,3'-diisopropylimidazolium-2-ylidene))(188) rhenium(V) hexafluorophosphate ((188) Re-4) via transmetalation us...
The higher homologues of group 7 transition metals, namely technetium and rhenium, offer radioisotopes suitable for the application as radiopharmaceuticals. Three generations of radiopharmaceuticals have been applied so far, with two of them reaching clinical application. While the first generation does not display a target specific functionality t...
Synthesis and Characterization of Imidazolium Salts with the Weakly Coordinating [B(C 6 F 5 ) 4 ] – Anion
Both enantiomers of the chiral rhodium-NHC complex [(4X, 5X)-1,3-bis[2,6-diisopropyl-phenyl]- 4,5-ditert-butylimidazolidine-2-ylidene][1,5-cyclooctadiene]-iodo-rhodium(I) with X = R, S were applied as catalysts for the asymmetric hydrosilylation of prochiral ketones. The influence of employed solvent, substrate, silane, and catalyst enantiomer on t...
It is shown that the introduction of sterically demanding ligands in lanthanoid metal complexes can depend more on the precise composition of the lanthanoid precursor than on the size of the new ligand. Thus, tris(r-butyl)methanol (“rmojt-H”) does not react with the amides Ln[N(SiMe 3 ) 2 ] 3 of the “late” (small) lanthanoid metals. However, fast a...
Carbene transfer from aliphatic diazoalkanes upon coordinatively unsaturated metal centers is a general synthetic concept that provides straight-forward routes into organo-metallic hydrocarbon chemistry. A comparison focussing on several key reactions of general applicability demonstrates that mononuclear organometal substrates add carbenes that ma...
The organorhenium(V) complexes (η5-C5Me5)ReX4 (2a, X = Cl; 2b, X = Br; Me = CH3) undergo stepwise dehalogenation upon treatment with various reducing agents, e.g. with HgCl2-activated aluminium powder, forming the isolable ReIV and ReIII dimers [η5-C5Me5)ReCl3]2 (3a) and [η5-C5Me5)ReX2]2 (4a, X = Cl;4b, X = Br), respectively. The weak metal-metal s...
The cationic diselenium bridged title compound 2 and [{(μ
Upon irradiation of C 5 H 5 V(CO) 4 in the presence of the Schiff base, derived from pyridine-carbaldehyde (2) and S-(—)-α-methylbenzyl-amine, two cis CO groups are replaced by the chelating ligand with the formation of complex 3. The reaction of C 5 H 5 W(CO) 3 Cl with 8-hydroxy-quinoline in boiling THF yields the oxinato complex 4. The analogous...
The metal metal distances of a representative number of organometallic manganese complexes vary from 2.50 Å to 3.23 Å, although all these compounds are predicted by the EAN Rule to possess single metal to metal bonds. It is no longer acceptable to predict bond orders from bond lengths, and vice versa.
The novel doubly bridged μ-methylene iron complexes μ-[C(H)CO2R]-μ-CO[(η5-C5H5)Fe(CO)]2 (R = C2H5: 3a; R = tC4H9: 3b) have been synthesized by low-temperature photolysis of the corresponding alkyldiazoacetates 2a and 2b, resp., in the presence of [(η5-C5H5)Fe(CO)2]2 (1) and characterized by means of their analytical data and IR, 1H NMR and mass spe...
Reaction of triirondodecacarbonyl (1) with the dinuclear chloroiridium complex [(η
The class of π-alkyne complexes of metals in medium and high oxidation states has been extended by the type CH 3 ReO 2 (RC≡CR′) (3a—i). Exchange of alkyne for oxo ligands under reducing conditions has been employed as a new general synthesis. Compounds 3 are thus obtained by reaction of methyltrioxorhenium(VII) (1) with the alkynes 2a—i in the pres...
Trimethylstannyl perrhenate, (CH3)3SnOReO3 (2), synthesized from dirheniumheptoxide and tetramethyltin, has a zigzag-chain crystal structure. This structure originates from catenation of individual molecules via the tin atom to a perrhenate group of another molecule. The tin atom thus forms the center of a trigonal-bipyramidal coordination geometry...
Reaction of (N-trimethylsilyl)-α-aminopicolin with the rhenium(V) oxohalogenide (η
Low temperature photolysis of (η
Ethyl diazoacetate (2 a) and tert-butyl diazoacetate (2 b) are converted into the metal stabilized, doubly bridging alkoxycarbonyl carbenes upon photolysis with (ƞ5-C5H5)Co(CO)2 (1) in tetrahydrofurane at -110°C. Although the yields of µ-dicarbonyl-µ-ethoxycarbonylmethylene- bis(ƞ5-cyclopentadienylcobalt) (3 a) and the corresponding ieri-butyl deri...
Iron is the most abundant transition metal in Earth's crust. It is relatively inexpensive, not very toxic, and environmentally benign. Undoubtedly, due to the involvement in a multitude of biological processes, which heavily rely on the rich functionalities of iron-containing enzymes, iron is one of the most important elements in nature. Additional...
a The synthesis and characterization of a library of imidazolium-based compounds of the type [R 1 R 2 R 3 im]Br (R 1 = H, CH 3 , benzyl (Bz), 1-(2,3,4,5,6-pentafluoro)benzyl (Bz F5); R 2 = H, CH 3 , C 2 H 5 ; R 3 = n-butyl, n-octyl) are reported. All compounds were characterized by means of 1 H and 13 C NMR spectroscopy, elemental analysis and sing...
Niobium(V) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide a The application of niobium(V) chloride and several imidazolium bromides as catalyst systems for the cycloaddition of propylene oxide (PO) with carbon dioxide to propylene carbonate (PC) is reported. A set of...
The combination of pentaerythritol with nucleophilic halide salts such as nBu4 NI is used as a dual catalyst system for the cycloaddition of carbon dioxide (CO2 ) with a broad range of organic epoxides yielding the respective cyclic carbonates. Due to synergistic effects of the organocatalysts, excellent yields and selectivities could be achieved u...
The reactions of dinuclear palladium precursors with the pyrazolato-bridged
bis(imidazolium) salt 3,5-bis(methylimidazolium-1-ylmethyl]-1H-pyrazole bis(hexafluorophosphate)
at different conditions are investigated to further explore the scope of this ligand class towards
multinuclear complexes. Depending on the reaction conditions, in dichlorometha...
Polyoxomolybdates were generated in situby teattng a carboxylic acid-functionalized ionic liquid with an aqueous solution of sodium molybdate. This reaction mixture was applied in the catalytic epoxidation of olefins using hydrogen peroxide as oxidant. The influence of acid and catalyst con-centration as well as of the reaction temperature was inve...
Methyldioxorhenium (MDO)-catalyzed CO bond cleavage of a variety of lignin β-O-4-model compounds yields phenolic and aldehydic compounds in homogeneous phase under mild reaction conditions. MDO is in situ generated by reduction of methyltrioxorhenium (MTO) and is remarkably stable under the applied reaction conditions allowing its reuse for least...
The combination of pentaerythritol with nucleophilic halide salts such as nBu4NI is used as a dual catalyst system for the cycloaddition of CO2 with a broad range of organic epoxides yielding the respective cyclic carbonates. Due to synergistic effects of the organocatalysts, excellent yields and selectivities could be achieved under mild reaction...
Twelve novel Re(i) acetonitrile complexes of the type [Re(CO)3(L)(MeCN)][WCA], with L being a chelating bis(NHC) ligand with alkylene-bridged and N-substituted bis(imidazolineylidene) moieties, and WCA (WCA = weakly coordinating anion) representing PF6(-) and [Al(OC(CF3)3)4](-), have been synthesized. 1D and 2D NMR spectroscopy as well as IR spectr...
The crystal structure of xylyltrioxorhenium has been determined and the applicability of the hybrid density functionals B3LYP, O3LYP, M06 and the gradient-corrected PBEPBE functional for predicting ground state geometries and vibrational energies of selected alkyl- and aryl Re(VII) trioxo compounds were evaluated. Different combinations of ECPs and...
The application of a ruthenium complex, bearing a sulfonated bis-N-heterocyclic carbene (NHC) ligand as catalyst precursor for the hydrogenation of aromatic compounds is reported. The reaction proceeds under mild conditions in aqueous phase. The treatment of the Ru complex with 40 bar H2 at 60 °C in water (0.1m KOH solution) leads to the formation...
The synthesis and an exemplary catalytic application of a SBA‐15‐supported rhodium–N‐heterocyclic carbene (NHC) complex is reported. In contrast to the conventional method of immobilization of unsaturated NHC complexes, the rhodium–NHC compound described here is connected to the SBA‐15 surface by a linker originating from the backbone of the unsatu...
On the way to clean biomass conversion The cover picture shows that oxygen functionalized arenes serve as model substrates for aromatic derivatives found for example in lignocellulosic biomass such as phenol or acetophenone. These arenes are hydrogenated to obtain the analogue cyclohexane derivatives in water. As precatalyst, a highly soluble sulfo...
Ring opening of various nickela- and palladalactones induced by the cleavage of the M-O bond by methyl trifluoromethanesulfonate (MeOTf) and methyl iodide (MeI) is examined. Experimental evidence supports the mechanism of ring opening by the alkylating agent followed by β-H elimination leading to methyl acrylate and a metal-hydride species. MeOTf s...
The dinuclear complex cis-[(CH3CN)(6)Mo-2(O2C-Fc)(2)(BF4)(2)] (2) and the square-shaped compound [(CH3CN)(4)Mo-2(O2C-Fc-CO2) (BF4)(2)](4) (3) can be synthesized by reacting [Mo-2(NCCH3)(10)][BF4](4) (1) with the corresponding ferrocenemonocarboxylic and -dicarboxylic acids (FMCA and FDCA) in a mixture of CH3CN and THF. The reaction of [Mo-2(NCCH3)(...
Pyrazolato-bridged dinuclear complexes of ruthenium and rhodium were synthesized from N-heterocyclic carbene (NHC) precursors, 3,5-bis[(methylimidazolium-1-yl)methyl]-1H-pyrazole bis(hexafluorophosphate), and the metal precursors [Ru(p-cymene)Cl-2](2) and [Rh(eta(5)-C5Me5)-Cl-2](2). Depending on the reaction conditions, dinuclear bis(imidazolium) c...
A novel method for the synthesis of 2-imidazolylpyridines is presented. The reaction of 2-halopyridines, potassium carbonate, and imidazole at high temperatures under inert gas atmosphere leads exclusively to the formation of 2-imidazolylpyridines in high yields. The synthesis is scalable, comparatively inexpensive, and the products are easily isol...
1,2,3-Triazolylidenes as versatile, strong donor ligands have currently experienced a boost in complex synthesis as well as catalytic applications. Although many examples of “abnormal” 1,2,3-triazolylidenes have been described, their “normal” congeners have been barely examined to date (for abnormal carbenes the resonance structures of the carbenes...
To date, only few examples of tetrazolylidene carbenes coordinated to transition metal complexes have been described. A direct comparison of "normal" tetrazolylidenes (1,4-substitution pattern) and "abnormal" tetrazolylidenes (also referred to as "mesoionic carbenes"; 1,3-substitution pattern) has not been performed at all. In this work, we describ...
Using new 'normal'-substituted 1,2,3-triazolylidene silver compounds as starting materials allowed for preparation of a series of molybdenum, ruthenium, rhodium, and palladium transition metal complexes bound to the new 1,2,3-triazolylidene ligand system. In this work, the first triazolylidene Mo compound is presented as well as the first structura...
Ionic compounds containing the polyoxomolybdate anion [Mo6O19](2-) and [(n-C4H9)(4)P](+) (tetra-butylphosphonium), [(n-C4H9)(3)P(n-C14H29)](+) (tributyl (tetradecyl)phosphonium), [Dbmim](+) (1-butyl-3-methylimidazolium) and [Dbmim] (1,2-dimethyl-3-butylimidazolium) cations were prepared and characterized, including the determination of three of the...
We provide an overview on the state-of-the-art in transition-metal complexes formed with water-soluble NHC ligands. Paths to introducing water solubility by ligand design are elucidated and some general properties of water-soluble NHC complexes are highlighted. The enhanced hydrophilicity of water-soluble catalysts offers advantages in applications...
This tutorial review summarizes all works and highlights recent advances published in the growing field of group 7 N-heterocyclic carbene (NHC) complexes. It provides a valuable source for all scientists that are interested in conducting research with new compounds bearing these metals. The article provides an overview of all manganese NHC complexe...
The synthesis of highly water soluble ruthenium(II) and osmium(II) complexes based on chelating N-heterocyclic carbene (NHC) ligands bearing sulfonated side chains is reported. The complexes are easily accessible in very good yields via synthesis of silver-bis(NHC) complexes and subsequent reaction with [(p-cymene)MCl2](2) (M = Ru, Os). They expres...
Dieser Aufsatz gibt eine Übersicht über Übergangsmetallkomplexe mit wasserlöslichen NHC‐Liganden. Bekannte Routen zur Einführung von Wasserlöslichkeit durch gezieltes Ligandendesign werden beleuchtet, und einige allgemeine Eigenschaften wasserlöslicher NHC‐Komplexen werden diskutiert. Die erhöhte Hydrophilie wasserlöslicher Katalysatoren bietet zus...
Polyoxomolybdates were generated in situ by treating a carboxylic acid-functionalized ionic liquid with an aqueous solution of sodium molybdate. This reaction mixture was applied in the catalytic epoxidation of olefins using hydrogen peroxide as oxidant. The influence of acid and catalyst concentration as well as of the reaction temperature was inv...
Cycloheptatrienylidene (CHT)-palladium complexes may react with N-donor molecules, showing two different pathways of reaction, either nucleophilic attack on the CHT ligand or coordination to the metal center. The first variant leads to a formation of water-soluble eta(3)-cycloheptatrienyl complexes, as in the case of 3,5-lutidine or 3-chloropyridin...
The hydrosilylation of allyl compounds is often accompanied by the formation of high amounts of byproducts. The formation processes have not been fully understood so far. In this work, the allyl hydrosilylation mechanism is investigated in detail and experimental and theoretical evidence for multiple, coexisting reaction pathways is provided. Based...
Three novel iron(II) complexes bearing tetradentate ligands of the type pyridine-bis(N-heterocyclic carbene) pyridine (NCCN) have been synthesized. The compounds trans-diacetonitrile[bis(o-imidazol-2-ylidenepyridine)alkane]iron(II) hexafluorophosphate (alkane = methane (2a), ethane (2b)) and cis-diacetonitrile[1,3-bis(o-imidazol-2-ylidenepyridine)p...
The synthesis of water-soluble Rh(I), Ir(I), and Ru(II) N-heterocyclic carbene complexes is described. These complexes are applied as catalysts for aqueous phase hydrogenation reactions. Good hydrogenation activities under ca. 40 atm pressure H2 at room temperature are observed.
A new ammonia adduct of a N-heterocyclic carbene (NHC) has been isolated, which can be used as a reagent for the synthesis of transition metal carbene complexes. It represents the first example of a 1,2,3-triazolylidene with a 1,2,4-substitution pattern, thus opening a new subclass ('normal' 1,2,3-triazolylidenes) of sterically and electronically t...
Treatment of propylperrhenate with 1 equiv. phenylzinc acetate yields dioxidodiphenylrhenium propionate. This novel complex can be synthesized with a yield of 41 % and is char-acterized by NMR and IR spectroscopy, as well as single-crystal X-ray diffraction. The compound is sensitive to moisture. It decomposes in sunlight and above 0 °C. The crysta...
Nine new complexes of the type fac-[(CO)(3)ReBr(L)], where L represents a chelating bis-NHC ligand consisting of two alkylene (propylene and butylene) bridged (R') N-substituted (R) imidazoline moieties (1,1'-di-R-3,3'-R'-diimidazolin-2,2'-diylidene), were synthesized. Spectroscopic methods, elemental analysis, mass spectrometry and X-ray crystallo...
Bridged rhodium(I) bis(NHC) complexes of the formula [bis-(NHC)Rh(I)PF6] (1c–5c) were synthesized and applied as catalysts in the transfer hydrogenation of acetophenone in 2-propanol. The activity of the rhodium(I) complexes largely depends on the nature of the N-substituents and the applied bases. The synthesized compounds were characterized by el...
Mu-nick: The methyl iodide-mediated ring opening of nickelalactones, which can be formed by oxidative coupling of carbon dioxide and ethylene at Ni0 complexes, induces β-H elimination, producing methyl acrylate in yields of up to 56 %. This reaction is found to be very sensitive to the ligands coordinated to the central nickel atom.
In der Vergangenheit wurde eine Vielzahl von Methoden zur Verwendung von Kohlendioxid in der organischen Synthese entwickelt. Trotz der breiten Gesamtverfügbarkeit von CO2 auf der Erde ist sein Einsatz als Reaktant, insbesondere in der Synthesechemie, recht selten. In den letzten 35 Jahren wurde intensiv daran geforscht, kosten- und energieeffizien...
The activation of carbon dioxide is one of the major tasks of catalysis today. CO2 is a ubiquitous and cheap C1 feedstock for the synthesis of raw and fine chemicals, yet its use as a reactant in industrial synthesis is comparatively scarce. The transformation of CO2 into acids, esters, lactones, and polymers with molecular transition-metal catalys...
A plethora of methods have been developed over the years so that carbon dioxide can be used as a reactant in organic synthesis. Given the abundance of this compound, its utilization in synthetic chemistry, particularly on an industrial scale, is still at a rather low level. In the last 35 years, considerable research has been performed to find cata...
Ionic liquids are an interesting alternative to classical solvents presenting several advantages. A variety of catalysts show good or even enhanced activities when applied in ionic liquids. Oxidation catalysis represents a large segment of industrial chemistry, providing both bulk chemicals and intermediates for high value added special products an...
To determine the functional and anatomic outcome of early surgical repair with vitrectomy and silicone oil in open-globe injuries with retinal detachment (RD).
Retrospective consecutive interventional case series.
All patients with open-globe injuries with RD treated between 1997 and 2007 underwent primary repair including vitrectomy with silicone...
Metal-organic frameworks (MOF) are becoming a more and more important class of functional materials. Yet, very often, the synthesis of MOFs is not easy to control and requires a profound knowledge and experience in solid state chemistry. One of the most frequently used metal connectors is the so-called 'paddle-wheel' (PW) unit, which is a well-know...
A series of chelating bridge functionalized bis-N-heterocyclic carbenes (NHC) complexes of rhodium (I) were prepared by reacting the corresponding imidazolium salts with [Rh(COD)Cl]2 in an in-situ reaction. For the N-methyl substituted complex with a PF6-anion an X-ray crystal structure was exemplary obtained. All complexes were spectroscopically c...
A detailed study investigating the mechanism of the hydrosilylation of 4-F-acetophenone by N-heterocyclic biscarbene rhodium(I) complexes was performed, delivering substantial experimental evidence for a recently proposed catalytic cycle and explaining the observed side-product formation. Labeling experiments, silylene trapping reactions, and speci...
New chiral bis(triazolium) salts have been prepared in good yields. The corresponding mononuclear platinum(II) complexes [Pt{bis(NHC)}X2] (X = Br, I) have been synthesized and spectroscopically characterized. One of the synthesized biscarbene complexes has also been characterised by X-ray crystallography. These complexes are efficient catalyst prec...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The synthesis and characterization of symmetrically substituted bis-N-heterocyclic carbene palladium(II) complexes with a functional group attached to the bridging moiety is described, as well as the immobilization of one of them on polystyrene Wang resin. The resulting complexes were tested both in homogeneous and heterogeneous Suzuki–Miyaura cros...
Over the last fifteen years, N-heterocyclic carbenes (NHCs) have mostly been used as ancillary ligands for the preparation of transition metal-based catalysts. Compared to phosphorus-containing ligands, NHCs tend to bind more strongly to metal centres, avoiding the necessity for the use of excess ligand in catalytic reactions. The corresponding com...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.