Synthesis of Natural Products and Related Compounds using Enyne
... (RCM). In 1999, Herrmann,[5] Nolan[6] and Grubbs[7] found the novel ruthenium carbene complexes 1d–g having a heterocyclic carbene as a ligand. Since these catalysts are very effective for olefin metathesis compared with the first-generation ruthenium catalysts 1b and 1c,[8] olefin metathesis has be ...
... (RCM). In 1999, Herrmann,[5] Nolan[6] and Grubbs[7] found the novel ruthenium carbene complexes 1d–g having a heterocyclic carbene as a ligand. Since these catalysts are very effective for olefin metathesis compared with the first-generation ruthenium catalysts 1b and 1c,[8] olefin metathesis has be ...
Migratory Insertion - vrg
... Normally this is a transition state structure for a hydride-alkene migratory insertion or a β-hydride elimination. In some cases, however, it can be observed as a ground-state stable structure. Because the C-H bond is sharing some of its σ-bond electron density with the metal, the C-H bond is weaken ...
... Normally this is a transition state structure for a hydride-alkene migratory insertion or a β-hydride elimination. In some cases, however, it can be observed as a ground-state stable structure. Because the C-H bond is sharing some of its σ-bond electron density with the metal, the C-H bond is weaken ...
VITA - Trace: Tennessee Research and Creative Exchange
... (left) and strong field donor ligands (right) with and without π-bonds. Several NHC complexes have been prepared which have four NHCs in one plane around a central metal atom, yet these examples mostly consist of four monodentate-NHCs or two bis-bidentate NHC ligands.12 ...
... (left) and strong field donor ligands (right) with and without π-bonds. Several NHC complexes have been prepared which have four NHCs in one plane around a central metal atom, yet these examples mostly consist of four monodentate-NHCs or two bis-bidentate NHC ligands.12 ...
Chemistry of vanadium-carbon single and double bonds Buijink, Jan
... and of mono(cyclopentadienyl) vanadium(III) alkylidenes. In chapter 2 the cyclopentadienyl ligand is temporarily not used. The attempted syntheses of homoleptic alkyl complexes of vanadium(III) is described, along with the reactivity of the mid and high-valent vanadium alkyl complexes that were obta ...
... and of mono(cyclopentadienyl) vanadium(III) alkylidenes. In chapter 2 the cyclopentadienyl ligand is temporarily not used. The attempted syntheses of homoleptic alkyl complexes of vanadium(III) is described, along with the reactivity of the mid and high-valent vanadium alkyl complexes that were obta ...
IOSR Journal of Applied Chemistry (IOSRJAC)
... A large number of transition metal complexes with various aliphatic, aromatic and heterocyclic dithiocarbamate ligands have been reported1. Dithiocarbamates are an important class of ligands, being capable of stabilising transition metals in a wide range of oxidation states. In by far the vast major ...
... A large number of transition metal complexes with various aliphatic, aromatic and heterocyclic dithiocarbamate ligands have been reported1. Dithiocarbamates are an important class of ligands, being capable of stabilising transition metals in a wide range of oxidation states. In by far the vast major ...
Terminal Cobalt(III) Imido Complexes Supported by Tris(Carbene
... orbital interactions,2 the bonding within the cobalt imido unit reported here is best described as a formal double bond.14 Interestingly, the DFT study also suggests that there is a considerable amount of electron density donated from one of the σ-orbitals of the carbenoid carbon into the π-orbital ...
... orbital interactions,2 the bonding within the cobalt imido unit reported here is best described as a formal double bond.14 Interestingly, the DFT study also suggests that there is a considerable amount of electron density donated from one of the σ-orbitals of the carbenoid carbon into the π-orbital ...
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... calculations 65 seem to indicate accumulation of negative charge on the 2- and 5-carbon atoms and a positive charge on the sulfur atom. Coordination can occur through the sulfur atom (8), through the 2- or 5-carbon or both (r] 1) or through the n-clouds of the C(2)=C(3) or C(4)=C(5) bonds (fl2) or b ...
... calculations 65 seem to indicate accumulation of negative charge on the 2- and 5-carbon atoms and a positive charge on the sulfur atom. Coordination can occur through the sulfur atom (8), through the 2- or 5-carbon or both (r] 1) or through the n-clouds of the C(2)=C(3) or C(4)=C(5) bonds (fl2) or b ...
Synthesis, structure and catalytic activity of NHC-Ag(I)
... an asymmetric, bidentate (2-) manner. Notably, no significant argentophilic interactions were observed in any of the acquired crystal structures (with Ag-Ag bond distance <3.44 Å).36 Ag-C bond lengths are within the expected range for similar complexes. In most cases, the Ag-C bond lengths are ca. ...
... an asymmetric, bidentate (2-) manner. Notably, no significant argentophilic interactions were observed in any of the acquired crystal structures (with Ag-Ag bond distance <3.44 Å).36 Ag-C bond lengths are within the expected range for similar complexes. In most cases, the Ag-C bond lengths are ca. ...
Palladium Complexes Containing Potentially
... Successful cleavage of the dimers was accomplished with methanolic HBr and produced the monometallic pyridylidene complexes 4a–c. An excess of HBr may be used without affecting the Pd–Cpyridylidene bond, thus suggesting a pronounced stability of this bond. In contrast, scission of the Pd–N bond of 4 ...
... Successful cleavage of the dimers was accomplished with methanolic HBr and produced the monometallic pyridylidene complexes 4a–c. An excess of HBr may be used without affecting the Pd–Cpyridylidene bond, thus suggesting a pronounced stability of this bond. In contrast, scission of the Pd–N bond of 4 ...
Chapter 4 (Phosphines)
... PMePh2 (136°), PMe2Ph (122°), PMe3 (118°), PEt3 (132°) P(Cy)3 (170°) tricyclohexylphosphine, P(t-Bu)3 (182°) • the alkyl phosphines are strong s-donors; low MW ones usually colorless liquids, somewhat to very air-sensitive, horrible smelling (unless very high MW and nonvolatile) Poor s-Donors, Good ...
... PMePh2 (136°), PMe2Ph (122°), PMe3 (118°), PEt3 (132°) P(Cy)3 (170°) tricyclohexylphosphine, P(t-Bu)3 (182°) • the alkyl phosphines are strong s-donors; low MW ones usually colorless liquids, somewhat to very air-sensitive, horrible smelling (unless very high MW and nonvolatile) Poor s-Donors, Good ...
CHEM 494 Lecture 10b - UIC Department of Chemistry
... Meissner 1819: To me it seems wholly appropriate to refer to those plant substances currently known by the names of alkalis, but alkaloids, since some of their properties they differ from alkalis considerably, and would thus find their place before the plant acids in the field of plant chemistry. Ja ...
... Meissner 1819: To me it seems wholly appropriate to refer to those plant substances currently known by the names of alkalis, but alkaloids, since some of their properties they differ from alkalis considerably, and would thus find their place before the plant acids in the field of plant chemistry. Ja ...
ALKANES – STRUCTURE, PROPERTIES, AND SYNTHESIS
... of strain present in different conformations in these systems, and use this information to explain relative stabilities. Important types of strain in conformational analysis are: o torsional strain (favors staggered conformations over eclipsed) o bond angle strain (which favors conformations with no ...
... of strain present in different conformations in these systems, and use this information to explain relative stabilities. Important types of strain in conformational analysis are: o torsional strain (favors staggered conformations over eclipsed) o bond angle strain (which favors conformations with no ...
FULL PAPER Cobalt(II), Nickel(II), Copper(II), and Zinc
... typical example of such a titration. Data were analyzed by Specfit[14] and factor analysis gave only two absorbing species for all the systems studied while absorbance versus metal/ligand ratios R displayed breaks at R ⫽ 1 (Figure S2, Supporting Information), so that under the experimental condition ...
... typical example of such a titration. Data were analyzed by Specfit[14] and factor analysis gave only two absorbing species for all the systems studied while absorbance versus metal/ligand ratios R displayed breaks at R ⫽ 1 (Figure S2, Supporting Information), so that under the experimental condition ...
Triruthenium and triosmium carbonyl clusters containing chiral
... and 2; S∼CH = 1-ethylenethiolate-3-H-4-(S)-phenylimidazolin2-ylidene; Scheme 2). Column chromatography and TLC failed to separate 1 and 2. A small amount (9%) of pure 2 was obtained by repeated recrystallization of the crude reaction mixture from combinations of dichloromethane and hexane. An X-ray ...
... and 2; S∼CH = 1-ethylenethiolate-3-H-4-(S)-phenylimidazolin2-ylidene; Scheme 2). Column chromatography and TLC failed to separate 1 and 2. A small amount (9%) of pure 2 was obtained by repeated recrystallization of the crude reaction mixture from combinations of dichloromethane and hexane. An X-ray ...
Coordination Chemistry Reviews 272 - Didier Astruc`s Library
... position. Subsequently, imidazole-based carbenes with the metal bonded at the C4(5) position were also first reported by Crabtree and co-workers (Fig. 2) [11]. These carbenes are called “abnormal” N-heterocyclic carbenes (aNHCs), and they are even stronger donors than C2-bound “normal” N-heterocycl ...
... position. Subsequently, imidazole-based carbenes with the metal bonded at the C4(5) position were also first reported by Crabtree and co-workers (Fig. 2) [11]. These carbenes are called “abnormal” N-heterocyclic carbenes (aNHCs), and they are even stronger donors than C2-bound “normal” N-heterocycl ...
here - University of Alberta
... (temperatures of around 120 °C) are required.35 Surprisingly, this reagent failed to metalate the ditriazolium compound 6 at temperatures below 100 °C, while at higher temperatures only decomposition occurred. Furthermore, our initial attempts to obtain the desired di-MIC-bridged homobimetallic Rh 2 ...
... (temperatures of around 120 °C) are required.35 Surprisingly, this reagent failed to metalate the ditriazolium compound 6 at temperatures below 100 °C, while at higher temperatures only decomposition occurred. Furthermore, our initial attempts to obtain the desired di-MIC-bridged homobimetallic Rh 2 ...
Lecture 1: Key Concepts in Stereoselective Synthesis
... For catalysts, the choice of ligands and metals are both important. To achieve good selectivity and reactivity, a wide range of ligands needs to be screened. However, complicated ligand structures usually require multiple synthetic steps, and it greatly limits their application. Therefore, the idea ...
... For catalysts, the choice of ligands and metals are both important. To achieve good selectivity and reactivity, a wide range of ligands needs to be screened. However, complicated ligand structures usually require multiple synthetic steps, and it greatly limits their application. Therefore, the idea ...
Isocyanide Chemistry
... • 1. General Reactivity of Isocyanide • 2. Heterocycle synthesis involving isocyanide • 3. Isocyanide in organometallics ...
... • 1. General Reactivity of Isocyanide • 2. Heterocycle synthesis involving isocyanide • 3. Isocyanide in organometallics ...
An insight into a base-free Michael addition reaction as catalyzed
... A] distances in comparison to the corresponding ones in the transition state TS1 [d/(NieC1) ¼ 1.865 A, d/(NieC7) ¼ 1.939 A and d/(Nie N3) ¼ 1.881 A] (Supporting information Fig. S7 and Table S4). The reaction proceeds by the approach of the methyl vinyl ketone (b) substrate to the Ni bound ace ...
... A] distances in comparison to the corresponding ones in the transition state TS1 [d/(NieC1) ¼ 1.865 A, d/(NieC7) ¼ 1.939 A and d/(Nie N3) ¼ 1.881 A] (Supporting information Fig. S7 and Table S4). The reaction proceeds by the approach of the methyl vinyl ketone (b) substrate to the Ni bound ace ...
Perspective and prospects for pincer ligand chemistry
... recent observation that the olefins produced in this reaction can undergo metathesis with Schrock alkylidenes to give re-distributated olefins which in turn are re-hydrogenated back to the saturated hydrocarbons, resulting in an overall ‘alkane metathesis’ process. This discovery has huge potential ...
... recent observation that the olefins produced in this reaction can undergo metathesis with Schrock alkylidenes to give re-distributated olefins which in turn are re-hydrogenated back to the saturated hydrocarbons, resulting in an overall ‘alkane metathesis’ process. This discovery has huge potential ...
Highly active iridium(I) complexes for catalytic hydrogen isotope
... a series of new iridium complexes which would deliver these objectives. Nolan6 and Buriak7 have elegantly established that manipulation of the ligand sphere around iridium can improve both stability and catalytic activity relative to Crabtree’s catalyst, albeit within the field of alkene hydrogenatio ...
... a series of new iridium complexes which would deliver these objectives. Nolan6 and Buriak7 have elegantly established that manipulation of the ligand sphere around iridium can improve both stability and catalytic activity relative to Crabtree’s catalyst, albeit within the field of alkene hydrogenatio ...
Title Regioselective Electrophilic C
... exclusively. Highly selective CPh–H bond activation was indicated by the clean NMR spectrum that revealed only a single isomer. Specifically, the presence of four distinct signals for the aromatic protons in the low-field region of the 1H NMR spectrum demonstrates desymmetrization of the N-bound phe ...
... exclusively. Highly selective CPh–H bond activation was indicated by the clean NMR spectrum that revealed only a single isomer. Specifically, the presence of four distinct signals for the aromatic protons in the low-field region of the 1H NMR spectrum demonstrates desymmetrization of the N-bound phe ...
Lecture 4- LIGANDS
... Alkynes behave in ways broadly similar to alkenes, but being more electronegative, they tend to encourage back donation and bind more strong The substituents tend to fold back away from the metal by 30–40 in the complex, and the M−C distances are slightly shorter than in the corresponding alkene com ...
... Alkynes behave in ways broadly similar to alkenes, but being more electronegative, they tend to encourage back donation and bind more strong The substituents tend to fold back away from the metal by 30–40 in the complex, and the M−C distances are slightly shorter than in the corresponding alkene com ...
C1 polymerization and related C-C bond forming - UvA-DARE
... react with a variety of diazo esters, but generally only a single insertion is observed.35,36 The reaction of ethyl diazoacetate (EDA; N2CHCO2Et) with B(Pr)3 yields for example only ethyl ester Pr−CH2CO2Et after aqueous work-up.37 The lack of multiple insertions is probably the result of the relativ ...
... react with a variety of diazo esters, but generally only a single insertion is observed.35,36 The reaction of ethyl diazoacetate (EDA; N2CHCO2Et) with B(Pr)3 yields for example only ethyl ester Pr−CH2CO2Et after aqueous work-up.37 The lack of multiple insertions is probably the result of the relativ ...
Reexamination of Aluminum Hydride as a Stereoselective Reducing
... ketones by aluminum hydride has been studied at different reaction temperature (0o, 25o and reflux) and the reactivity and the isomeric ratio of the product mixture are summarized in Table 1. When the reduction of monocyclic ketones was carried out at 0o, the thermodynamically more stable isomer alc ...
... ketones by aluminum hydride has been studied at different reaction temperature (0o, 25o and reflux) and the reactivity and the isomeric ratio of the product mixture are summarized in Table 1. When the reduction of monocyclic ketones was carried out at 0o, the thermodynamically more stable isomer alc ...
Persistent carbene
A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the 'R's are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.Traditionally carbenes are viewed as so reactive that were only studied indirectly, e.g. by trapping reactions. This situation has changed dramatically with the emergence of persistent carbenes. Although they are fairly reactive substances, i.e., undergoing dimerization, many can be isolated as pure substances.Persistent carbenes can exist in the singlet or the triplet states with the singlet state carbenes being more stable. The relative stability of these compounds is only partly due to steric hindrance by bulky groups. Some singlet carbenes are thermodynamically stable in the absence of moisture and (in most cases) oxygen, and can be isolated and indefinitely stored. Others are not thermodynamically stable and will dimerise slowly over days. The less stable triplet state carbenes have half-lives measured in seconds, and therefore can be observed but not stored.