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  • 1.
    Alvi, Muhammad Rouf
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Burkhard O., Jahn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Computational Investigation of Brook-Type Silabenzenes and Their Possible Formation through [1,3]-Si -> O Silyl Shifts2013Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, nr 1, s. 16-28Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    Arkhypchuk, Anna I.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Santoni, Marie-Pierre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Ott, Sascha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Revisiting the Phospha-Wittig - Horner Reaction2012Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 31, nr 3, s. 1118-1126Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Bökman, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Gogoll, Adolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Bohman, Ove
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Pettersson, L. G. M.
    UNIV STOCKHOLM, DEPT THEORET PHYS, S-11346 STOCKHOLM, SWEDEN.
    Siegbahn, Hans O. G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen.
    Electronic Structure of Catalytically Important Palladium Complexes Studied by Photoelectron Spectroscopy1992Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 11, nr 5, s. 1784-1788Artikel i tidskrift (Refereegranskat)
  • 4. 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.2009Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 28, nr 1, s. 123-131Artikel i tidskrift (Refereegranskat)
    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)]

  • 5.
    Church, Tamara L.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Rasmussen, Torben
    Andersson, Pher G.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Enantioselectivity in the Iridium-Catalyzed Hydrogenation of Unfunctionalized Olefins2010Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, nr 24, s. 6769-6781Artikel i tidskrift (Refereegranskat)
    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

  • 6.
    Eklöf, Anders M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Guliashvili, Tamaz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Relation between the π-Contribution to Reversed Si═C Bond Polarization and the Reaction Profile for the Thermolytic Formation of Silenes2008Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, nr 20, s. 5203-5211Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Eklöf, Anders M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Gullashvili, Tarnaz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Relation between the pi-Contribution to Reversed Si=C Bond Polarization and the Reaction Profile for the Thermolytic Formation of Silenes2008Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 27, nr 20, s. 5203-5211Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Emanuelsson, Rikard
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Denisova, Aleksandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Baumgartner, Judith
    Institut für Chemie, Universität Graz.
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Optimization of the Cyclic Cross-Hyperconjugation in 1,4-Ditetrelcyclohexa-2,5-dienes2014Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 33, nr 12, s. 2997-3004Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Gogoll, Adolf
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
    Gomes, João
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
    Bergkvist, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
    Grennberg, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
    Configurational Assignment of Acyclic (π-Allyl)Palladium Complexes: Analytical Application of Chelating Nitrogen Ligands1995Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 14, nr 3, s. 1354-1364s. 1354-1364Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Gogoll, Adolf
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen.
    Grennberg, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Axen, Andreas
    Uppsala universitet.
    (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)-pal1997Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 16, nr 6, s. 1167-1178s. 1167-1178Artikel i tidskrift (Refereegranskat)
    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

  • 11.
    Grennberg, Helena
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Gogoll, Adolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Bäckvall, Jan-Erling
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi.
    Acid‑Induced Transformation of Palladium(0)­‑Benzoquinone Complexes to Palladium(II) and Hydroquinone1993Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 12, nr 5, s. 1790-1793Artikel i tidskrift (Refereegranskat)
  • 12. Ohshita, Joji
    et al.
    Kawamoto, Hiroyuki
    Kunai, Atsutaka
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi.
    Formation of Acylsilenolates from Bis(acyl)trisilanes as the Silicon Analogues of Acylenolates2010Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 29, nr 18, s. 4199-4202Artikel i tidskrift (Refereegranskat)
    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.

  • 13. 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.2007Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, nr 11, s. 2840-2848Artikel i tidskrift (Refereegranskat)
    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)]

  • 14.
    Sawadjoon, Supaporn
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Orthaber, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Sjöberg, Per J. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Eriksson, Lars
    Samec, Joseph S. M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    Equilibrium Study of Pd(dba)2 and P(OPh)3 in the Pd-Catalyzed Allylation of Aniline by Allyl Alcohol2014Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 33, nr 1, s. 249-253Artikel i tidskrift (Refereegranskat)
    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.

  • 15.
    Svensson, Fredrik
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Mane, Rajendra S.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Sävmarker, Jonas
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Larhed, Mats
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Sköld, Christian
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för läkemedelskemi, Avdelningen för organisk farmaceutisk kemi.
    Theoretical and Experimental Investigation of Palladium(II)-Catalyzed Decarboxylative Addition of Arenecarboxylic Acid to Nitrile2013Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, nr 2, s. 490-497Artikel i tidskrift (Refereegranskat)
    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.

  • 16.
    Wallner, Andreas
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Emanuelsson, Rikard
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Baumgartner, Judith
    Marschner, Christoph
    Ottosson, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Fysikalisk-organisk kemi.
    Coupling of Disilane and Trisilane Segments Through Zero, One, Two, and Three Disilanyl Bridges in Cyclic and Bicyclic Saturated Carbosilanes2013Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 32, nr 2, s. 396-405Artikel i tidskrift (Refereegranskat)
    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.

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