Change search
Refine search result
1 - 41 of 41
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlquist, Mårten
    et al.
    Scripps Research Insititute.
    Fokin, Valery V.
    Enhanced reactivity of dinuclear Copper(I) acetylides in dipolar cycloadditions2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 18, p. 4389-4391Article in journal (Refereed)
    Abstract [en]

    Dinuclear alkynyl copper(I) complexes exhibit superior reactivity toward organic azides compared to their monomeric analogues. DFT studies indicate that the second copper center facilitates the formation of the cupracycle in the rate-determining step and stabilizes the metallacycle intermediate itself. These findings support the experimentally determined rate law and shed light on the origin of high reactivity of the in situ generated copper acetylides.

  • 2.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Fristrup, P
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    Theoretical evidence for low-ligated palladium(0): [Pd-L] as the active species in oxidative addition reactions2006In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, no 8, p. 2066-2073Article in journal (Refereed)
    Abstract [en]

    The oxidative addition of PhI to Pd-O has been studied by DFT with a continuum representation of the solvent. It is shown that the preferred number of ligands on palladium is lower than would be expected from "conventional wisdom" and the 18-electron rule. The most favored oxidative addition is obtained when Pd is coordinated by only the aryl iodide and one additional ligand in a linear arrangement. The calculations indicate that p-orbitals on the central metal are not involved in bonding in any of the complexes described herein, in good agreement with classic ligand field theory and also with a recent bonding analysis by Weinhold and Landis, but in apparent violation of the 18-electron rule.

  • 3.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Kozuch, S
    Shaik, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    On the performance of continuum solvation models for the solvation energy of small anions2006In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, no 1, p. 45-47Article in journal (Refereed)
    Abstract [en]

    The determination of continuum solvation models for the solvation energy of anions, was described. To investigate the reliability of the solvent model, a few explicit THF molecules were incorporated. A set of anions was chosen for which the experimental free energiesof solvation were available for both H 2O and DMSO solutions. A major difference between the water model and the DMSO model is that the latter systematically overestimates the free energy of solvation. The full water model in Jaguar v 4.2, including also nonelectrostatic terms, gives good correlation with experimental values for energy of solvation.

  • 4.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Norrby, Per-Ola
    Göteborg University.
    Oxidative addition of aryl chlorides to monoligated palladium(0): A DFT-SCRF study2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 3, p. 550-553Article in journal (Refereed)
    Abstract [en]

    Oxidative addition of aryl chlorides to palladium has been investigated by hybrid density functional theory methods (B3LYP), including a continuum model describing the solvent implicitly. A series of para-substituted aryl chlorides were studied to see the influence of electronic effects on the reaction. It was found that the experimentally observed higher reactivity of the more electron deficient aryl chlorides is due to their ability to accept back-donation from Pd-0 and form reasonably strong pre-reactive complexes. This effect is less pronounced in the transition state; when it is measured from the pre-reactive complex, the barrier to oxidative addition is actually higher for the electron-deficient aryl chlorides, but the overall reaction barrier is still lower than for the electron-rich aryl chlorides.

  • 5.
    Alvi, Muhammad Rouf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Burkhard O., Jahn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Computational Investigation of Brook-Type Silabenzenes and Their Possible Formation through [1,3]-Si -> O Silyl Shifts2013In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, no 1, p. 16-28Article in journal (Refereed)
    Abstract [en]

    Quantum chemical calculations with the M062X hybrid meta density functional theory method were performed in order to examine formation of Brook-type silabenzenes 4a 4l, silapyridines 6a 6d, and five-membered ring silaheteroaromatics 8a8d through [1,3]-trimethylsilyl (TMS) and [1,3]-tri(isopropyl)silyl (TIPS) shifts from a tetrahedral silicon atom to an adjacent carbonyl oxygen of cyclic conjugated acylsilane precursors. All Brook-type silabenzenes and silapyridines, having a 2-trialkylsiloxy substituent, are at lower relative energies than their precursors, whereas silaheteroaromatics 8a 8d are found at slightly higher energies. The free energies of activation for the thermal [1,3]-TMS shifts range from 29 to 44 kcal/mol, with the lowest for a Brook-type silapyridine and the highest for a silafuran. The geometries of the Brook-type silabenzenes, silapyridines, silafuran and silathiophene indicate aromatic character, but the silapyrroles are nonaromatic. At M062X/6-311+G(d)//M062X/6-31G(d) level all Brook-type silabenzene dimers studied herein are more stable than two silabenzenes, also for a silabenzene with bulky TIPS, OTIPS and tert-butyl substituents (4l). Yet, comparisons of the B3LYP/6-31G(d) dimerization energies of 4l with that of the isolable 1-Tbt-silabenzene (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) of Tokitoh [J. Chin. Chem. Soc. 2008, 55, 487] indicate that 4l will also be a monomeric silabenzene, and thus, a suitable synthetic target.

  • 6. Andrew, Rhiann E.
    et al.
    Ferdani, Dominic W.
    Ohlin, C. Andre
    Chaplin, Adrian B.
    Coordination Induced Atropisomerism in an NHC-Based Rhodium Macrocycle2015In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 34, no 5, p. 913-917Article in journal (Refereed)
    Abstract [en]

    Reversible interaction with carbon monoxide results in the onset of dynamic atropisomerism at 298 K in an otherwise static NHC-based rhodium pincer complex, [Rh(C boolean AND N boolean AND C-(CH2)(12))(CO)][BArF4] (1, ArF = 3,5-C6H3(CF3)(2)). The mechanism of this process has been comprehensively interrogated by a combination of variable-temperature NMR spectroscopy, IR spectroscopy, and computational modeling. In addition, a structural analogue of a high-energy symmetrical intermediate species-invoked in the process but not directly observed spectroscopically-has been prepared and characterized in solution and the solid-state.

  • 7.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Santoni, Marie-Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Revisiting the Phospha-Wittig - Horner Reaction2012In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, no 3, p. 1118-1126Article in journal (Refereed)
    Abstract [en]

    P,P-Dichlorophosphines 2a-c (RPCl2, R = Ph (a), t-Bu (b), 2,4,6-Me3Ph (c)) and P,P-dibromophosphines 4d,e (RPBr2, R = (i-Pr)(3)SiC C (d) and H2C=CH (e)) react with triethylphosphite under Michaelis-Arbuzov conditions to give phosphinodiphosphonates 3a-e in quantitative yields. After complexation to W(CO)(5) and treatment with CH3ONa, phospha-Wittig-Horner reagents 9a,b are obtained on a multigram scale in good overall yield. Phospha-Wittig-Horner reagents with unsaturated, substituents at P-III (10d,e) can be prepared in analogous procedures; however, their prevail in an unusual ylide form that allows conjugation between the lone pair and the acetylene and vinyl pi-systems, respectively. Phosphinophosphonate 9a has been characterized by X-ray crystallography and is shown to react smoothly with acetone within minutes. The resulting W(CO)(5)-coordinated phosphaalkene is shown to dimerize to a 1,2-diphosphitane or to undergo a 1,3-proton shift depending on the reaction conditions. In addition, a one-pot synthetic sequence starting from W(CO)(5)-coordinated phosphinodiphosphonates 5d,e has been developed to engage compounds with vinyl and acetylene substituents in phospha-Wittig-Horner reactions.

  • 8.
    Bökman, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Bohman, Ove
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Pettersson, L. G. M.
    UNIV STOCKHOLM, DEPT THEORET PHYS, S-11346 STOCKHOLM, SWEDEN.
    Siegbahn, Hans O. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics.
    Electronic Structure of Catalytically Important Palladium Complexes Studied by Photoelectron Spectroscopy1992In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 11, no 5, p. 1784-1788Article in journal (Refereed)
  • 9.
    Carlsson, Marcus
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Chemistry.
    One-pot synthesis of trans mono- or diarylalkynyl substituted platinum(II) compounds with tertiary phosphine or phosphite ligands2006In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, no 22, p. 5500-5502Article in journal (Refereed)
    Abstract [en]

    An efficient one-pot synthesis has been developed for preparation of trans-mono- or diarylalkynyl bisphosphine or bisphosphite Pt(II) compounds. In the procedure, the alkyne and the tertiary phosphorus ligands are mixed with PtCl2 in tetrahydrofuran and triethylamine solution. CuI is added for synthesis of disubstituted complexes, but the catalyst is not used for preparation of monosubstituted complexes. Microwave irradiation is preferably employed to give the trans-mono- or diarylalkynyl Pt(II) compound in short time and high yield.

  • 10. Casey, Charles P.
    et al.
    Boller, Timothy M.
    Samec, Joseph S. M.
    Reinert-Nash, John R.
    Quantitative Determination of the Regioselectivity of Nucleophilic Addition to η3-Propargyl Rhenium Complexes and Direct Observation of an Equilibrium between η3-Propargyl Rhenium Complexes and Rhenacyclobutenes.2009In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 28, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    PMe3 adds selectively to the central C of the η3-propargyl complex [C5Me5(CO)2Re(η3-CH2C≡CCMe3)][BF4] (1-t-Bu) to form the metallacyclobutene [C5Me5(CO)2Re(CH2C(PMe3):CCMe3)][BF4] (7). The rate of rearrangement of the metallacyclobutene 7 to η2-alkyne complex [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)][BF4] (8) is independent of phosphine concn., consistent with a dissociative mechanism proceeding via η3-propargyl complex 1-t-Bu. The rate of this rearrangement is 480 times slower than the rate of exchange of PMe3 with the labeled metallacyclobutene 7-d9. This rate ratio provides an indirect measurement of the regioselectivity for addn. of PMe3 to the central C of η3-propargyl complex 1-t-Bu to give 7 compared to addn. to a terminal C to give 8. The addn. of PPh3 to 1-t-Bu gives the metallacyclobutene [C5Me5(CO)2Re(CH2C(PPh3):CCMe3)][BF4] (11). Low-temp. 1H NMR spectra provide evidence for an equil. between metallacyclobutene 11 and η3-propargyl complex 1-t-Bu (Keq ≈ 44 M-1 at -46° and ΔG°(0°) = -1.2 ± 0.2 kcal mol-1). The crystal and mol. structures of [C5Me5(CO)2Re[η2-(Ar2PCH2CH2PPh2)CH2C≡CCMe3]][BF4]·2CH2Cl2 (Ar = 3,5-(CF3)2C6H3) and [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)]Cl·H2O were detd. by x-ray crystallog. [on SciFinder(R)]

  • 11. Cheng, Mu-Jeng
    et al.
    Nielsen, Robert J.
    Ahlquist, Mårten
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Goddard, William A., III
    Carbon-Oxygen Bond Forming Mechanisms in Rhenium Oxo-Alkyl Complexes2010In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, no 9, p. 2026-2033Article in journal (Refereed)
    Abstract [en]

    Three C X bond formation mechanisms observed in the oxidation of (HBpz(3))ReO(R)(OTf) [HBpz(3) = hydrotris(1-pyrazolypborate; R = Me, Et, and iPr; OTf = OSO(2)CF(3)] by dimethyl sulfoxide (DMSO) were investigated using quantum mechanics (M06//B3LYP DFT) combined with solvation (using the PBF Poisson Boltzmann polarizable continuum solvent model). For R = Et we find the alkyl group is activated through alpha-hydrogen abstraction by external base OTf(-) with a free energy barrier of only 12.0 kcal/mol, leading to formation of acetaldehyde. Alternatively, ethyl migration across the M=O bond (leading to the formation of acetaldehyde and ethanol) poses a free energy barrier of 22.1 kcal/mol, and the previously proposed alpha-hydrogen transfer to oxo (a 2+2 forbidden reaction) poses a barrier of 44.9 kcal/mol. The rate-determining step to formation of the final product acetaldehyde is an oxygen atom transfer from DMSO to the ethylidene, with a free energy barrier of 15.3 kcal/mol. When R = iPr, the alkyl 1,2-migration pathway becomes the more favorable pathway (both kinetically and thermodynamically), with a free energy barrier (Delta G(double dagger) = 11.8 kcal/mol) lower than alpha-hydrogen abstraction by OTf(-) (Delta G(double dagger) = 13.5 kcal/mol). This suggests the feasibility of utilizing this type of migration to functionalize M-R to M-OR. We also considered the nucleophilic attack of water and ammonia on the Re-ethylidene alpha-carbon as a means of recovering two-electron-oxidized products from an alkane oxidation. Nucleophilic attack (with internal deprotonation of the nucleophile) is exothermic. However, the subsequent protonolysis of the Re alkyl bond (to liberate an alcohol or amine) poses a barrier of 37.0 or 42.4 kcal/mol, respectively. Where comparisons are possible, calculated free energies agree very well with experimental measurements.

  • 12.
    Church, Tamara L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Rasmussen, Torben
    Andersson, Pher G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Enantioselectivity in the Iridium-Catalyzed Hydrogenation of Unfunctionalized Olefins2010In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, no 24, p. 6769-6781Article in journal (Refereed)
    Abstract [en]

    The iridium catalyzed asymmetric hydrogenation of largely unfunctionalized olefins has been studied by DFT calculations using a full experimentally tested combination of ligand and substrate All possible diastereomeric pathways were considered within four different hydrogenation mechanisms The effect of a solvent continuum was also considered and both the gas phase and solvent continuum calculations favored the same mechanism This mechanism passed through Ir-III and Ir-V intermediates and was consistent with the sense of stereoselection observed experimentally Comparing the calculations to those performed on a model system permitted an evaluation of the model system s utility in representing the full one A simple general method for predicting the sense of stereoselection in iridium-catalyzed olefin hydrogenation was developed and tested against published data

  • 13.
    Eklöf, Anders M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Guliashvili, Tamaz
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Relation between the π-Contribution to Reversed Si═C Bond Polarization and the Reaction Profile for the Thermolytic Formation of Silenes2008In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, no 20, p. 5203-5211Article in journal (Refereed)
    Abstract [en]

    A quantum chemical investigation of the reaction profiles for the thermal formation of silenes Z2Si═C(XSiH3)Y from silanes Z2(H3Si)Si−C(═X)Y (X = O, S, NMe; Y = NMe2, OMe, SMe, Me; Z = SiH3, Me) has been performed. Focus was put on the influence of the π-conjugative contribution to reversed Si═C bond polarization (Siδ−═Cδ+) as determined by natural resonance theory (NRT) at the B3LYP density functional theory level. Good linear correlations between the weights of π-conjugated reverse polarized resonance structures (ΣΦRP(π)) in the electronic structure and the Si═C bond lengths were found for the two classes of silenes with Z = SiH3 and Me (r2 = 0.957 and 0.955, respectively). Silenes that are strongly influenced by the π-conjugative reverse polarization have low barriers for back-reaction to the silanes, making these silenes more difficult to isolate when formed through a [1,3]-silyl shift than those that are naturally polarized. Modest exponential dependencies of the activation barriers for the reverse reactions on ΣΦRP(π) are found (r2 = 0.685 for Z = SiH3 and r2 = 0.699 for Z = Me). Species with the silyl groups replaced by trimethylsilyl groups, e.g., the Brook-type silene (Me3Si)2Si═C(OSiMe3)t-Bu, have lower contributions of ΣΦRP(π) by 3−23% than the corresponding model silenes, a result of steric bulk. The weight ΣΦRP(π) to the electronic structure of (Me3Si)2Si═C(OSiMe3)t-Bu was calculated to be 7.4%. With Z = Me, the silenes are in general not equally influenced by ΣΦRP(π) as with Z = SiH3, their energies relative to the silanes are higher, and they have higher activation barriers for both forward and backward reactions.

  • 14.
    Eklöf, Anders M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Gullashvili, Tarnaz
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Relation between the pi-Contribution to Reversed Si=C Bond Polarization and the Reaction Profile for the Thermolytic Formation of Silenes2008In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, no 20, p. 5203-5211Article in journal (Refereed)
    Abstract [en]

    A quantum chemical investigation of the reaction profiles for the thermal formation of silenes Z(2)Si=C(XSiH3)Y from silanes Z(2)(H3Si)Si-C(=X)Y (X = O, S, NMe; Y = NMe2, OMe, SMe, Me; Z = SiH3, Me) has been performed. Focus was put on the influence of the pi-conjugative contribution to reversed Si=C bond polarization (Si delta-=C delta+) as determined by natural resonance theory (NRT) at the B3LYP density functional theory level. Good linear correlations between the weights of pi-conjugated reverse polarized resonance structures (Sigma Phi(RP)(pi)) in the electronic structure and the Si=C bond lengths were found for the two classes of silenes with Z = SiH3 and Me (r(2) = 0.957 and 0.955, respectively). Silenes that are strongly influenced by the pi-conjugative reverse polarization have low barriers for back-reaction to the silanes, making these silenes more difficult to isolate when formed through a [1,3]-silyl shift than those that are naturally polarized. Modest exponential dependencies of the activation barriers for the reverse reactions on Sigma Phi(RP)(pi) are found (r(2) = 0.685 for Z = SiH3 and r(2) = 0.699 for Z = Me). Species with the silyl groups replaced by trimethylsilyl groups, e.g., the Brook-type silene (Me3Si)(2)Si=C(OSi-Me-3)t-Bu, have lower contributions of Sigma Phi(RP)(pi) by 3-23% than the corresponding model silenes, a result of steric bulk. The weight Sigma Phi(RP)(pi) to the electronic structure of (Me3Si)(2)Si=C(OSiMe3)t-Bu was calculated to be 7.4%. With Z = Me, the silenes are in general not equally influenced by Sigma Phi(RP)(pi) as with Z = SiH3, their energies relative to the silanes are higher, and they have higher activation barriers for both forward and backward reactions.

  • 15.
    Emanuelsson, Rikard
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Denisova, Aleksandra
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Baumgartner, Judith
    Institut für Chemie, Universität Graz.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Optimization of the Cyclic Cross-Hyperconjugation in 1,4-Ditetrelcyclohexa-2,5-dienes2014In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 33, no 12, p. 2997-3004Article in journal (Refereed)
    Abstract [en]

    Cyclic cross-hyperconjugation can exist to variable extents in 1,4-ditetrelcyclohexa-2,5-dienes, i.e., all-carbon cyclohexa-1,4-dienes and 1,4-disila/digerma/distanna/diplumbacyclohexa-2,5-dienes. In this study we first use density functional theory (DFT) computations to optimize the conjugation strength by seeking the optimal atom E and substituent group E'Me-3 in the two saturated E(E'Me-3)(2) moieties (E and E' as the same or different tetrel (group 14) elements). We reveal that the all-carbon cyclohexadienes with gradually heavier E'Me-3 substituents at the two saturated carbon atoms display significant cross-hyperconjugation. The first electronic excitations in these compounds, which formally have two isolated C=C bonds, are calculated to reach wavelengths as long as 400 nm (excitation energies of 3.1 eV). These transitions are mostly forbidden, and the lowest allowed transitions are found at 387 nm (3.2 eV). The silicon analogues are also cross-hyperconjugated, while a decline is observed in the 1,4-digerma/distanna/diplumbacyclohexa-2,5-diene. Experiments on two substituted 1,4-disilacyclohexa-2,5-dienes confirm the effect of the E'Me3 substituents, with regard to both electronic excitations and geometries as determined by UV absorption spectroscopy and X-ray crystallography, respectively. At the end, we reveal through computations how electron-donating and electron-withdrawing substituents at the C=C double bonds influence the electronic properties of the all-carbon ring. We find that the first calculated excitation, which is forbidden, can be shifted to 440 nm (2.83 eV). This shows to what extent cyclic cross-hyperconjugation can affect the electronic and optical properties of a compound with two formally isolated C=C double bonds.

  • 16.
    Gogoll, Adolf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Gomes, João
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Bergkvist, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry I.
    Configurational Assignment of Acyclic (π-Allyl)Palladium Complexes: Analytical Application of Chelating Nitrogen Ligands1995In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 14, no 3, p. 1354-1364p. 1354-1364Article in journal (Refereed)
    Abstract [en]

    A method for assignment of the relative stereochemistry in acyclic pi-allyl)palladium complexes by H-1 NMR H-H coupling constants has been developed. It is based on the introduction of nitrogen chelating ligands of the bipyridyl type into the complexes. The analytical suitability of several other types of nitrogen chelating ligands has also been investigated. A model for rationalization of the observed relation between stereochemistry and spectral parameters is proposed. Introduction of the chelating ligand also affects the syn,anti equilibrium of the complexes. Isomer ratios depend upon the relative stereochemistry of the side chain as well as on the chelating ligand.

  • 17.
    Gogoll, Adolf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Axen, Andreas
    Uppsala University.
    (π-Allyl)palladium complexes with N,N'-diphenylbispidinone derivatives as a new type of chelating nitrogen ligand: Complexation studies, spectroscopic properties, and an x-ray structure of (3,7-diphenyl-1,5-dimethylbispidinone)[(1,3-η(3)-propenyl)-pal1997In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 16, no 6, p. 1167-1178p. 1167-1178Article in journal (Refereed)
    Abstract [en]

    A series of 3,7-diazabicyclo[3.3.1]nonane (bispidine) derivatives have been synthesized, and their properties as bidentate nitrogen ligands for (pi-allyl)palladium complexes have been investigated. Complexes of these ligands and of N,N'-diphenylpiperazin

  • 18.
    González Miera, Greco
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martínez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Acceptorless Alcohol Dehydrogenation: OH vs NH Effect in Bifunctional NHC–Ir(III) Complexes2018In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 37, no 5, p. 636-644Article in journal (Refereed)
    Abstract [en]

    Bifunctional complexes bearing N-heterocyclic carbene (NHC) ligands functionalized with hydroxy or amine groups were synthesized to measure the beneficial effect of different modes of metal–ligand cooperation in the acceptorless dehydrogenation of alcohols. In comparison to complexes with an amine moiety, hydroxy-functionalized iridium catalysts showed superior activity. In contrast to alcohols, 1,4-diols underwent cyclization to give the corresponding tetrahydrofurans without involving dehydrogenation processes. Mechanistic investigations to rationalize the “OH effect” in these types of complexes have been undertaken.

  • 19.
    Grennberg, Helena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Gogoll, Adolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Bäckvall, Jan-Erling
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Acid‑Induced Transformation of Palladium(0)­‑Benzoquinone Complexes to Palladium(II) and Hydroquinone1993In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 12, no 5, p. 1790-1793Article in journal (Refereed)
  • 20. Haeffner, F.
    et al.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    How does methyllithium invert? A density functional study2001In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, no 24, p. 5134-5138Article in journal (Refereed)
    Abstract [en]

    Quantum chemical studies (B3LYP) of the inversion of methyllithium in both tetrameric and dimeric aggregates have been carried out. Results show that inversion occurs either via dissociation of the tetramer into the dimers, passage of a four-membered-ring transition state, and association of the dimers to form the inverted tetramer, or via a nonconcerted route involving an eight-membered-ring transition state. The activation energies of these two mechanisms are similar. However, the dissociative mechanism is ruled out by NMR experiments.

  • 21. Johnson, Magnus T.
    et al.
    Johansson, Roger
    Kondrashov, Mikhail V.
    Steyl, Gideon
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Roodt, Andreas
    Wendt, Ola F.
    Mechanisms of the CO2 Insertion into (PCP) Palladium Allyl and Methyl sigma-Bonds. A Kinetic and Computational Study2010In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, no 16, p. 3521-3529Article in journal (Refereed)
    Abstract [en]

    The reaction of the sigma-bonded (PCP)Pd-Me complex (PCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with CO2 is first-order in palladium and first-order in CO, with a rate constant k(s) = 8.9 +/- 0.8 M-1 s(-1) at 353 K. Activation parameters are Delta H double dagger = 73 7 kJ/mol and Delta S double dagger = 118 +/- 19 J/K mol. Based on this and theoretical calculations we propose an S(E)2 mechanism where the coordinated methyl group attacks a completely noncoordinated carbon dioxide molecule in a bimolecular reaction. The PCPPd-crotyl complex was synthesized in an 65:35 E:Z mixture, and it was shown to react with CO, to give the complex PCPPd-O(CO)CH(CH3)CHCH2 as a single isomer, where the former gamma-carbon has been carboxylated. Theoretical calculations again suggest an S(E)2 mechanism with a noncoordinated carbon dioxide reacting with the terminal carbon on the allyl group, forming an eta(2)-bonded olefin complex as an intermediate. The rearrangement of this intermediate to the O-bonded product is concluded to be rate determining. The crystal structure of PCPPd-O(CO)C(CH3)(2)CHCH2 is reported and as well as the solubility of carbon dioxide in benzene-d(6) at different pressures and temperatures.

  • 22.
    Kalek, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-catalyzed C-P bond formation: Mechanistic studies on the ligand substitution and the reductive elimination. An intramolecular catalysis by the acetate group in PdII complexes2008In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, no 22, p. 5876-5888Article in journal (Refereed)
    Abstract [en]

    Ligand substitution and reductive elimination of the palladium-catalyzed C−P bond forming cross-coupling were investigated in depth. It was found that for PhPdII(PPh3)2X (X = I, Br, Cl) complexes, a step commonly referred to as ligand substitution commenced with coordination of an H-phosphonate diester, followed by its deprotonation to form an equilibrium mixture of penta- and tetracoordinate palladiumphosphonate intermediates, from which reductive elimination of the product (diethyl phenylphosphonate) occurred. For the acetate counterpart, PhPdII(PPh3)2(OAc), the incorporation of a phosphonate moiety to the complex was preceded by a rate-determining removal of the supporting phosphine ligand, facilitated by an intramolecular catalysis by the acetate group. Both the reaction steps, i.e., formation of palladiumphosphonate intermediates and reductive elimination, were significantly faster for the acetate versus halides containing PdII complexes investigated. Similar observations were found to be true also for bidentate ligand complexes [(dppp)PdII(Ph)X]; however, in this instance, a single palladiumphosphonate intermediate, (dppp)PdII(Ph)(PO(OEt)2), could be observed by 31P NMR spectroscopy. The synthetic and kinetic studies on the cross-coupling reaction of diethyl H-phosphonate with phenyl halides permitted us to elucidate a crucial catalytic role of an acetate group in PdII complexes and to propose two distinctive catalytic cycles, which complemented traditional Pd0/PdII schemes, for the palladium-mediated C−P bond formation.

  • 23.
    Kalek, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pd(0)-Catalyzed phosphorus-carbon bond formation: Mechanistic and synthetic studies on the role of the palladium sources and anionic additives2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 24, p. 5840-5847Article in journal (Refereed)
    Abstract [en]

    Pd(PPh3)4, Pd(dba)2, Pd(OAc)2, and PdCl2, have been evaluated as possible Pd(0) sources for the palladium-catalyzed P−C bond formation via a cross-coupling of aryl halides with H-phosphonate diesters. It was found that the most efficient catalytic system can be generated from Pd(OAc)2 with a key role being played by Pd(II) and Pd(0) species with coordinated acetate ions. The reactivity of differently ligated Pd(II) complexes was determined, and 31P NMR spectroscopy studies were carried out to provide mechanistic interpretations for the observed differences between the catalytic systems.

  • 24. Kleimark, Jonatan
    et al.
    Johansson, Charlotte
    Olsson, Susanne
    Håkansson, Mikael
    Hansson, Sverker
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Norrby, Per-Ola
    Sterically goverend selectivity in palladium-assisted allylic alkylation2011In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 30, p. 230-238Article in journal (Refereed)
    Abstract [en]

    The selectivity in the Pd-assisted allylic alkylation has been investigated in a system with a ligand tethered to the allylic moiety. Isolation of (η3-allyl)Pd complexes and stoichiometric reaction with malonate nucleophiles allowed separation of various factors influencing the regioselectivity in a system that cannot undergo apparent rotation. Unexpectedly, trans effects were found to have only a minor influence on the selectivity, whereas changing the tether length could shift the preference from favored internal to dominant terminal attack. DFT-assisted analysis revealed that the dominant selectivity-determiningfactors are the forced rotation of the allylic moiety and an important steric repulsion from a syn-alkyl substituent

  • 25.
    Niclas, Solin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism of the η3-η1-η3 Isomerization in Allylpalladium Complexes: Solvent Coordination, Ligand, and Substituent Effects2001In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, p. 5464-5471Article in journal (Refereed)
    Abstract [en]

    The mechanism of the η3 → η1 → η3 isomerization of (η3-allyl)palladium complexes occurring as catalytic intermediates in important synthetic transformations has been studied by applying density functional theory at the B3PW91(DZ+P) level. It was found that under catalytic conditions, in the condensed phase, the isomerization process involves tetracoordinated (η1-allyl)palladium intermediates. In these intermediates a solvent molecule or another ancillary ligand coordinates to palladium. The stability of the (η1-allyl)palladium intermediates critically depends on the electronic effects and on the coordination ability of the solvent molecules and the ancillary ligands. The theoretical calculations indicate a dσ → π* type hyperconjugative interaction occurring in the η1-allyl moiety of the intermediary complexes. These hyperconjugative interactions influence the structure of the complexes and the activation barrier to rotation through the C1−C2 bond. Alkyl substitution of the metalated carbon leads to destabilization of the (η1-allyl)palladium complexes, which increases the activation energy of the syn/anti isomerization process. This substituent effect arises from a dual steric and electronic destabilizing interaction between the methyl substituent and the metal atom.

  • 26. Ohshita, Joji
    et al.
    Kawamoto, Hiroyuki
    Kunai, Atsutaka
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Formation of Acylsilenolates from Bis(acyl)trisilanes as the Silicon Analogues of Acylenolates2010In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, no 18, p. 4199-4202Article in journal (Refereed)
    Abstract [en]

    Reactions of bis(acyl)trisilanes with tris(trimethylsilyl)silyllithium in THF, followed by treatment of the resulting dark red solutions with alkyl halides, gave the Si-alkylated products and tetrakis(trimethylsilyl)silane, indicating the formation of lithium acylsilenolates via Si-Li exchange. Exo-thermic formation of lithium acylsilenolate was demonstrated by DFT calculations on a model reaction.

  • 27. Osadchuk, Irina
    et al.
    Tamm, Toomas
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Theoretical Investigation of a Parallel Catalytic Cycle in CO2 Hydrogenation by (PNP)IrH32015In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 34, no 20, p. 4932-4940Article in journal (Refereed)
    Abstract [en]

    The (PNP)IrH3 (2,6-bis(diisopropylphosp-hinomethyl)pyridine iridium trihydride) complex by Nozaki is a highly active and selective catalyst for CO2 hydrogenation to formic acid in aqueous KOH. Previous theoretical investigations found that regeneration of the catalyst is the rate-determining step in this reaction. In the current article we present results from a computational study using density func- theory in order to consider the possibility of sequential insertion of two CO2 molecules in two Ir-H bonds before the reaction with hydrogen. We found that insertion of a second CO2 molecule is indeed possible; moreover, this sequential insertion allows formation of a more electrophilic iridium mono-hydride intermediate, and thereby the process of H-2 cleavage is facilitated. In addition, we considered the influence of ligands coplanar with the PNP ligand on the energy of CO2 insertion into the (PNP)IrH2X complex and found that sigma- and pi-donating ligands promote the reaction.

  • 28. Polukeev, Alexey V.
    et al.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO).
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Iridium Hydride Complexes with Cyclohexyl-Based Pincer Ligands: Fluxionality and Deuterium Exchange2016In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 35, no 16, p. 2600-2608Article in journal (Refereed)
    Abstract [en]

    Two hydride compounds with aliphatic pincer ligands, (PCyP)IrH2 (PCyP = {cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane}(-) (1) and (PCyP)IrH4 (2), have been studied, with emphasis on features where such systems differ from arene-based analogues. Both compounds reveal relatively rapid exchange between alpha-C-H and Ir-H, which can occur via formation of carbene or through demetalation, with nearly equal barriers. This observation is confirmed by deuterium incorporation into the alpha-C-H position. Complex 1 can reversibly add an N-2 molecule, which competes with the alpha-agostic bond for a coordination site at iridium. The hydrogen binding mode in tetrahydride 2 is discussed on the basis of NMR and IR spectra, as well as DFT calculations. While the interpretation of the data is somewhat ambiguous, the best model seems to be a tetrahydride with minor contribution from a dihydrido-dihydrogen complex. In addition, the catalytic activity of 1 in deuterium exchange using benzene-d(6) as a deuterium source is presented.

  • 29.
    Privalov, Timofei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Linde, C.
    Zetterberg, K.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Theoretical studies of the mechanism of aerobic alcohol oxidation with palladium catalyst systems2005In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 24, no 5, p. 885-893Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) was applied to a comprehensive mechanistic study of the Pd(II)-catalyzed oxidation of alcohols by molecular oxygen. Both parts of the catalytic cycle, i.e., the oxidative dehydrogenation of the substrate and the regeneration of the catalyst by the co-oxidant, molecular oxygen, were studied. The catalytic cycle under consideration consists of intramolecular deprotonation, beta-hydride elimination, and migratory insertion steps, and it is relevant for a wide class of catalytic systems. In particular, a Pd(II) cyclometalated system was addressed and qualitatively compared with the Uemura system (Pd(OAc)(2)/pyridine) and with the Pd-carbene system. Geometries of the intermediate complexes and relative Gibbs free energies were identified along the proposed reaction path with the help of computational methods. The transition state for the beta-hydride elimination, which is the highest point on the energy profile of the catalytic cycle, was identified.

  • 30.
    Privalov, Timofei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Samec, Joseph S. M.
    Backvall, Jan- E.
    DFT study of an inner-sphere mechanism in the hydrogen transfer from a hydroxycyclopentadienyl ruthenium hydride to imines2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 11, p. 2840-2848Article in journal (Refereed)
    Abstract [en]

    A combination of the DFT method with the computational description of environmental effects by solvent was applied to a theoretical study of the hydrogen transfer to imines by [2,3,4,5-Ph-4(eta(5)-C4COH)Ru(CO)(2)H] (2) within a molecular model that closely mimics the authentic reaction conditions. A consistent polarizable continuum solvent model (PCM) was instrumental and necessary in achieving stability of the computational model. Environmental effects by solvent were also considered in an extended model with an addition of explicit solvent molecules within the PCM. The study elucidates an inner-sphere mechanism in detail. Intermediate complexes and transition states are characterized. Three distinct energy barriers along the reaction coordinate are predicted when solvent effects are taken into account. The imine coordinates to ruthenium via ring slippage with an energy barrier of about 15 kcal/mol. Close in energy (12 kcal/mol) is the transition state of the hydride transfer, which gives an (eta(2)-cyclopentadienone)ruthenium amine intermediate. The presence of Ph groups on the Cp ring facilitates the ring slippage that occurs on imine coordination. This eta(2)-intermediate finally rearranges to the corresponding (eta(4)-cyclopentadienone)ruthenium amine complex via a transition state at 9 kcal/mol. The stable ruthenium amine complex was verified against an X-ray structure of the corresponding complex. Inclusion of the solvent (by PCM or explicit molecules) was required to stabilize low-hapticity intermediates and transition state structures.

  • 31. Privalov, Timofei
    et al.
    Samec, Joseph S. M.
    Baeckvall, Jan-E.
    DFT study of an inner-sphere mechanism in the hydrogen transfer from a hydroxycyclopentadienyl ruthenium hydride to imines.2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 11, p. 2840-2848Article in journal (Refereed)
    Abstract [en]

    A combination of the DFT method with the computational description of environmental effects by solvent was applied to a theor. study of the H transfer to imines by [2,3,4,5-Ph4(η5-C4COH)Ru(CO)2H] (2) within a mol. model that closely mimics the authentic reaction conditions. A consistent polarizable continuum solvent model (PCM) was instrumental and necessary in achieving stability of the computational model. Environmental effects by solvent were also considered in an extended model with an addn. of explicit solvent mols. within the PCM. The study elucidates an inner-sphere mechanism. Intermediate complexes and transition states were characterized. Three distinct energy barriers along the reaction coordinate are predicted when solvent effects are taken into account. The imine coordinates to Ru via ring slippage with an energy barrier of ∌15 kcal/mol. Close in energy (12 kcal/mol) is the transition state of the hydride transfer, which gives an (η2-cyclopentadienone)ruthenium amine intermediate. The presence of Ph groups on the Cp ring facilitates the ring slippage that occurs on imine coordination. This η2-intermediate finally rearranges to the corresponding (η4-cyclopentadienone)ruthenium amine complex via a transition state at 9 kcal/mol. The stable Ru amine complex was verified against an x-ray structure of the corresponding complex. Inclusion of the solvent (by PCM or explicit mols.) was required to stabilize low-hapticity intermediates and transition state structures. [on SciFinder(R)]

  • 32. Ryabov, A. D.
    et al.
    Panyashkina, I. M.
    Polyakov, V. A.
    Fischer, Andreas
    KTH, Superseded Departments, Chemistry.
    Access to central carbon chirality through cycloplatination of 1-(2-pyridinylthio)propanone by cis- PtCl2(S-SOMe(p-tolyl)) . The crystal structure of (SsSc)- Pt{py{SCHC(O)Me}-2}Cl(SOMe(p-tolyl))2002In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 21, no 8, p. 1633-1636Article in journal (Refereed)
    Abstract [en]

    Cycloplatination of the prochiral sp(3)C-H bond of 1-(2-pyridinylthio)propanone (py(SCH2C(O)Me)(-2), 1a) by cis-[PtCl2(SOMe2)] in dry ethanol affords [Pt(py(SCHC(O)Me)-2)Cl(SOMe2)] (3a) in 77% isolated yield without any side product. The same reaction using the chiral complex cis-[PtCl2(S-SOMe(p-tolyl))] (the absolute configuration of sulfur is indicated for the coordinated ligand) leads to two cycloplatinated diastereoisomers, 4a (SsRc) and 4b (SsSc), in 12.9 and 33.7% yield, respectively (de 44.6%). Their absolute configuration was deduced from the analysis of the H-1 NMR spectra and confirmed by an X-ray structural investigation of 4b. Diastereomer 4b was shown to react with PPh3 to give the enantiomer [Pt(py(SCHC(O)Me)-2)Cl(PPh3)] with the central carbon chirality only. Rather surprisingly, attempted cycloplatination Of py(SCH2C(O)Ph)-2 (1b) by cis-[PtCl2(SOMe2)] affords the cycloplatinated complex [Pt(pyf(SCHC(O)Ph)-2)Cl(SOMe2)] (3b) in a miserable yield.

  • 33.
    Sawadjoon, Supaporn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sjöberg, Per J. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Eriksson, Lars
    Samec, Joseph S. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Equilibrium Study of Pd(dba)2 and P(OPh)3 in the Pd-Catalyzed Allylation of Aniline by Allyl Alcohol2014In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 33, no 1, p. 249-253Article in journal (Refereed)
    Abstract [en]

    Reaction of Pd(dba)2 and P(OPh)3 shows a unique equilibrium where the Pd[P(OPh)3]3 complex is favored over both Pd(dba)[P(OPh)3]2 and Pd[P(OPh)3]4 complexes at room temperature. At a lower temperature, Pd[P(OPh)3]4 becomes the most abundant complex in solution. X-ray studies of Pd[P(OPh)3]3 and Pd(dba)[P(OPh)3]2 complexes show that both complexes have a trigonal geometry with a Pd–P distance of 2.25 Å due to the π-acidity of the phosphite ligand. In solution, pure Pd(dba)[P(OPh)3]2 complex equilibrates to the favored Pd[P(OPh)3]3 complex, which is the most stable complex of those studied, and also forms the most active catalytic species. This catalyst precursor dissociates one ligand to give the reactive Pd[P(OPh)3]2, which performs an oxidative addition of nonmanipulated allyl alcohol to generate the π-allyl-Pd[P(OPh)3]2 intermediate according to ESI-MS studies.

  • 34. Sawadjoon, Supaporn
    et al.
    Orthaber, Andreas
    Sjöberg, Per J. R.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Samec, Joseph S. M.
    Equilibrium Study of Pd(dba)(2) and P(OPh)(3) in the Pd-Catalyzed Allylation of Aniline by Allyl Alcohol2014In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 33, no 1, p. 249-253Article in journal (Refereed)
    Abstract [en]

    Reaction of Pd(dba)(2) and P(OPh)(3) shows a unique equilibrium where the Pd[P(OPh)(3)](3) complex is favored over both Pd(dba)[P(OPh)(3)](2) and Pd[P(OPh)(3)](4) complexes at room temperature. At a lower temperature, Pd[P(OPh)(3)](4) becomes the most abundant complex in solution. X-ray studies of Pd[P(OPh)(3)](3) and Pd(dba)[P(OPh)(3)](2) complexes show that both complexes have a trigonal geometry with a Pd-P distance of 2.25 angstrom due to the pi-acidity of the phosphite ligand. In solution, pure Pd(dba)[P(OPh)(3)](2) complex equilibrates to the favored Pd[P(OPh)(3)](3) complex, which is the most stable complex of those studied, and also forms the most active catalytic species. This catalyst precursor dissociates one ligand to give the reactive Pd[P(OPh)(3)](2), which performs an oxidative addition of nonmanipulated allyl alcohol to generate the pi-allyl-Pd[P(OPh)(3)](2) intermediate according to ESI-MS

  • 35. Stokes, F.A.
    et al.
    Less, R.J.
    Haywood, J.
    Melen, Rebecca L.
    Thompson, R.L.
    Wheatley, A.E.
    Wright, D.S.
    Johansson, Adam Johannes
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Structure and Bonding of the Manganese(II) Phosphide Complex (t-BuPH(2))(eta(5)-Cp)Mn{mu-(t-BuPH)}(2)Mn(Cp)(t-BuPH(2))2012In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, no 1, p. 23-26Article in journal (Refereed)
    Abstract [en]

    Rather than achieving bis-deprotonation of the phosphine, reaction of Cp2Mn (Cp = cyclopentadienyl) with t-BuPH2 at room temperature yields monodeprotonation of half of the available phosphine in the product (t-BuPH2)(η5-Cp)Mn{μ-(t-BuPH)}2Mn(Cp)(t-BuPH2) (1). This complex comprises a Mn(II) phosphide and is a dimer in the solid state, containing a Mn2P2 diamond core. Consistent with the observation of a relatively short intermetal distance of 2.8717(4) Å in 1, DFT analysis of the full structure points to a singlet ground state stabilized by a direct Mn–Mn single bond. This is in line with the diamagnetic character of 1 and an 18-electron count at Mn.

  • 36.
    Svensson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Mane, Rajendra S.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Sävmarker, Jonas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Larhed, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Sköld, Christian
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Organic Pharmaceutical Chemistry.
    Theoretical and Experimental Investigation of Palladium(II)-Catalyzed Decarboxylative Addition of Arenecarboxylic Acid to Nitrile2013In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, no 2, p. 490-497Article in journal (Refereed)
    Abstract [en]

    The reaction mechanism of palladium(II)-catalyzed decarboxylative addition of 2,6-dimethoxybenzoic acid to acetonitrile was investigated by means of density functional theory (DFT) calculations. Calculations of the free energy profile for decarboxylation and carbopalladation indicated carbopalladation as the rate-determining step of the reaction. Investigation of the free energy profile for a series of experimentally evaluated nitrogen-based bidentate palladium ligands revealed that higher energy is required for decarboxylation and carbopalladation employing the experimentally least efficient ligand. The DFT investigation also showed that the relative free energies of the transition states were lowered in polar solvent, and preparative experiments confirmed that a nonoptimal ligand could be greatly improved by addition of water to the reaction system.

  • 37.
    Theveau, Laure
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Bellini, Rosalba
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Dydio, Pawel
    Szabo, Zoltan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    van der Werf, Angela
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Amsterdam, Netherlands.
    Sander, Robin Afshin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Reek, Joost N. H.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Cofactor-Controlled Chirality of Tropoisomeric Ligand2016In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 35, no 11, p. 1956-1963Article in journal (Refereed)
    Abstract [en]

    A new tropos ligand with an integrated anion receptor receptor site has been prepared. Chiral carboxylate and phosphate anions that bind in the anion receptor unit proved capable of stabilizing chiral conformations of the achiral flexible bidentate biaryl phosphite ligand, as shown by variable temperature H-1 and P-31 NMR spectroscopical studies of palladium(0) olefin complexes. Palladium allyl complexes of the supramolecular ligand-chiral cofactor assemblies catalyzed asymmetric allylic substitutions of rac-(E)-1,3-diphenyl-2-propenyl carbonate and rac-3-cyclohexenyl carbonate with malonate and benzylamine as nucleophiles to provide nonracemic products. Although moderate enantioselectivities were observed, (ee:s up to 66%), the results confirm the ability of the anionic guests to affect the conformation of the ligand.

  • 38.
    Wallner, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Emanuelsson, Rikard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Baumgartner, Judith
    Marschner, Christoph
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Coupling of Disilane and Trisilane Segments Through Zero, One, Two, and Three Disilanyl Bridges in Cyclic and Bicyclic Saturated Carbosilanes2013In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, no 2, p. 396-405Article in journal (Refereed)
    Abstract [en]

    Several six-membered cyclic and [2.2.2]bicyclic organo-silanes with varying proportions of silicon atoms in the bridges have been prepared following a stepwise approach that exploits dianionic polysilanes. Focus in our analysis was placed on the bicyclic compounds which all have silicon atoms at the bridgehead positions. Quantum chemical calculations of these compounds revealed the possibility to enhance the coupling through a single cisoid tetrasilane cage segment by replacing one or two of the other -SiMe2SiMe2- bridges with -CH2CH2- bridges. UV absorption spectroscopy revealed a red shift in the lowest visible transitions when going from a bicyclo[2.2.2]octane with three -SiMe2SiMe2- bridges to those with two or one such bridge. However, these red shifts are deceptive, as the lowest vertically excited singlet states, which are dark according to TD-DFT calculations, do not display the same trend. Still, since these compounds have (i) excellent structural rigidity, (ii) provide potentials for functionalization through their exocyclic trimethylsilyl groups, and (iii) display electronic structure variations with the number of -SiMe2SiMe2- bridges, they could be interesting for further studies: e.g., in single-molecule electronics.

  • 39.
    Wang, Ying
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Zhan, Shaoqi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Nucleophilic Attack by OH2 or OH-: A Detailed Investigation on pH Dependent Performance of a Ru Catalyst2019In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 38, no 6, p. 1264-1268Article in journal (Refereed)
    Abstract [en]

    The considerable rate enhancements along with the increase in pH values may be due to the direct involvement of hydroxide anion in attacking electrophilic [Ru-V(tda)(py)(2)O](+) (1; tda = [2,2':6',2 ''-terpyridine]-6,6 ''-dicarboxylate, py = pyridine). The enhanced reaction rate is well in agreement with the descending activation barriers in our calculation. The addition of four extra water molecules in the geometry optimization plays a key role in stabilizing hydroxide anion as well as building a reasonable hydrogen-bonding network, and three of these molecules are required to stabilize the OH as an anion instead of a radical.

  • 40.
    Westlund, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Vestberg, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Glimsdal, Eirik
    Lindgren, Mikael
    Lopes, Cesar
    Malmström, Eva E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Synthesis and Characterization of a 3-Arm Star Platinum(II) Acetylide Chromophore Targeted for Optical Limiting ApplicationsIn: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041Article in journal (Other academic)
  • 41. Zierkiewicz, W.
    et al.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A theoretical study of the essential role of DMSO as a solvent/ligand in the Pd(OAc)(2)/DMSO catalyst system for aerobic oxidation2005In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 24, no 24, p. 6019-6028Article in journal (Refereed)
    Abstract [en]

    Dimethyl sulfoxide (DMSO) has unique properties as an aprotic, polar solvent. The oxygen atom in DMSO can interact with positive charges and thus stabilize metal cation. The sulfur atom, although somewhat positively charged, does not interact with negative charges effectively. Also, two methyl groups surround the sulfur atom and influence binding properties of DMSO. These features of DMSO are addressed in the present computational study of the Pd(AcO)(2)/DMSO-catalyzed aerobic oxidation system. Mechanistic and computational details are provided. The step-by-step Gibbs energy of reaction was calculated using the electronic energy at the B3LYP density functional level with thermal functions calculated at the same level of theory. The solvent was modeled using the polarized medium (PCM) with additional DMSO molecules in the second coordination sphere of the complexes studied. The overall reaction pathway was divided into several steps in accord with available experimental data. All steps, including the first deprotonation and the beta-hydride elimination transition states, were elucidated in good detail. Coordination and reorganization of DMSO in Pd(II)(AcO)(2)/DMSO and Pd(0)/(DMSO)(n) complexes has been studied to provide realistic data about coordination of DMSO with hard (O) versus soft (S) ligand donor atoms. The P-hydride elimination transition state was identified computationally to give an estimation of the activation energy of the alcohol oxidation reaction. Therefore, we suggest that the rate-determining step is related to the alcohol part of the reaction cycle.

1 - 41 of 41
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf