Microwave spectra of [13C] and [15N] pyridine N-oxides and a preliminary ring structure

Snerling, Ole; Nielson, Claus Jórgen; Nygaars, Lise; Pedersen, Erik; Sørensen, Georg

doi:10.1016/0022-2860(75)85138-6

Cited by 27 publications

(4 citation statements)

References 9 publications

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“…Pyridine N -oxide- d 5 was prepared to allow generation of [(HBpz 3 )ReO 2 (Ph)]OTf without extraneous peaks in the aromatic region of the 1 H NMR. It was prepared according to the literature procedure used previously for other labeled pyridine N -oxides …”

Section: Methodsmentioning

confidence: 99%

Phenyl-to-Oxo Migration in an Electrophilic Rhenium(VII) Dioxo Complex

1996

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Reaction of (HBpz3)ReO(Ph)(OTf) with oxygen atom donors leads to oxidation of the phenyl group [HBpz3 = hydrotris(1-pyrazolyl)borate, OTf = triflate, OSO2CF3]. Reaction with Me2SO gives the adduct [(HBpz3)ReO(Ph)(OSMe2)]OTf, which undergoes phenyl-to-oxo migration at 25 °C to give the phenoxide complex [(HBpz3)ReO(OPh)(OSMe2)]OTf and Me2S. The Me2SO adduct readily and reversibly loses Me2S (k = 2.9(4) s-1 at 25 °C) as indicated by isotope exchange reactions and magnetization transfer. The Me2SO adduct also slowly oxidizes Me2SO to Me2SO2. These reactions all proceed via an intermediate rhenium(VII) dioxo complex, [(HBpz3)ReO2(Ph)]OTf. This dioxo complex can be observed at low temperature on reaction of (HBpz3)ReO(Ph)(OTf) with pyridine N-oxide. It rearranges at 0 °C by phenyl-to-oxo migration to give phenoxide products and the catecholate complex (HBpz3)ReO(O2C6H4). The kinetics of this migration have been measured (ΔH ⧧ = 14.8(7) kcal/mol, ΔS ⧧ = −20.5(25) eu). From these data and the activation parameters for reactions of [(HBpz3)ReO(Ph)(OSMe2)]OTf, a detailed free energy surface for the reactions of [(HBpz3)ReO2(Ph)]OTf is constructed. The dioxo complex reacts very rapidly with Me2S (1.7 × 105 M-1 s-1) with essentially no enthalpic barrier, consistent with the action of a highly electrophilic oxo ligand. Electrophilicity of the oxo groups is suggested to be a critical factor in facilitating the phenyl-to-oxo migration. A general explanation for the relative ease of various organometallic migration reactions, based on analogies with organic [1,2]-shifts, is presented.

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Section: Methodsmentioning

confidence: 99%

Phenyl-to-Oxo Migration in an Electrophilic Rhenium(VII) Dioxo Complex

1996

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“…In our hands, it is only practicable to use CCSD(T) for first states of each symmetry; in order to include both the 1 2 B 1 and 2 2 B 1 states, we used SA-MCSCF, as well. For the calculated structure of theX 1 A 1 state, the average differences in bond lengths and angles from the MW substitution structure [5][6][7][8] are 0.0014 Å and 0.30…”

Section: A the Ground And Cationic Structuresmentioning

confidence: 99%

“…More details of the subset of calculated Rydberg states are given in Table II. Least squares fit between the observed Rydberg state energies in column 1 (x) and the calculated ones in column 6 (y) with form: y = A + Bx has A = −0.54 (48) and B = 1.06 (6), where the standard deviations for the last digit are given. The median and maximum absolute errors are 0.26 and 0.52 eV.…”

Section: B Rydberg State Identification In the Vuv Spectrummentioning

confidence: 99%

“…1, abbreviated to PyNO) is the simplest N-oxide of the azines, a class of fully conjugated heterocyclic compounds. [1][2][3][4] The importance of PyNO is demonstrated by the number of studies of its molecular structure, with several microwave (MW) substitution structures (having differing isotopic compositions), [5][6][7][8] electron diffraction (ED), 9 and x-ray diffraction 10 studies. The N-oxides are obtained by the oxidation of the corresponding azines such as pyridine (2 in Fig.…”

Section: Introductionmentioning

confidence: 99%

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The electronic states of pyridine-N-oxide studied by VUV photoabsorption and ab initio configuration interaction computations

Palmer

Hoffmann

Jones

et al. 2013

The Journal of Chemical Physics

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The first vacuum-ultraviolet absorption spectrum of pyridine-N-oxide has been obtained, and has led to the identification of nearly 30 Rydberg states. These states were identified by use of the vibrational envelope ("footprint") of the UV-photoelectron spectrum, and are based on the first to the third ionization energies (IE). The adiabatic IE order, central to the Rydberg state symmetry identification, is confirmed by multi-configuration SCF calculations as: 1 2 B 1 < 1 2 B 2 < 1 2 A 2 < 2 2 B 1 . Several excited valence state equilibrium structures were determined by multi-configuration SCF and coupled cluster procedures. Multi-reference multi-root CI was used to calculate both Rydberg and valence state vertical excitation energies and oscillator strengths, which were correlated with the experimental measurements. © 2013 AIP Publishing LLC. [http://dx

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