Synthesis and photoelectron spectroscopic studies of N(CH 2CH2NMe)3P=E (E = O, S, NH, CH2)

Tamás Kárpáti, Tamás Veszprémi, Natesan Thirupathi, Xiaodong Liu, Zhigang Wang, Arkady Ellern, László Nyulászi, John G. Verkade

Research output: Contribution to journalArticle

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Abstract

The synthesis and the crystal and molecular structure of N(CH 2CH2NMe)3P=CH2 is reported. The P-Nax distance is rather long in N(CH2CH 2NMe)3P=CH2. The ylide N(CH2CH 2NMe)3P=CH2 proved to be a stronger proton acceptor than proazaphosphatrane N(CH2CH2NMe) 3P, since it was shown to deprotonate N(CH2CH 2NMe)3PH+. The extremely strong basicity of the ylide is in accordance with its low ionization energy (6.3 eV), which is the lowest in the presently investigated series N(CH2CH 2NMe)3P=E (E: CH2, NH, lone pair, O and S), and to the best of our knowledge it is the smallest value observed for a non-conjugated phosphorus ylide. Computations reveal the existence of two bond strech isomers, and the stabilization of the phosphorus centered cation by electron donation from the equatorial and the axial nitrogens. Similar stabilizing effects operate in the case of protonation of E. A fine balance of these different interactions determines the P-Nax distance, which is thus very sensitive to the level of the theory applied. According to the quantum mechanical calculations, methyl substitution at the equatorial nitrogens flattens the pyramidality of this atom, increasing its electron donor capability. As a consequence, the PNax distance in the short-transannular bonded protonated systems and the radical cations is longer by about 0.5 Å in the Neq(Me) than in the Neq(H) systems. Accordingly, isodesmic reaction energies show that a stabilization of about 25 and 10 kcal/mol is attributable to the formation of the transannular bond in case of Neq(H) and the experimentally realizable N eq(Me) species, respectively.

Original languageEnglish
Pages (from-to)1500-1512
Number of pages13
JournalJournal of the American Chemical Society
Volume128
Issue number5
DOIs
Publication statusPublished - Feb 8 2006

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Photoelectrons
Phosphorus
Cations
Nitrogen
Stabilization
Positive ions
Electrons
Ionization potential
Protonation
Alkalinity
Molecular Structure
Isomers
Molecular structure
Protons
Substitution reactions
Crystal structure
Atoms
P(CH(3)NCH(2)CH(2))(3)N

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Synthesis and photoelectron spectroscopic studies of N(CH 2CH2NMe)3P=E (E = O, S, NH, CH2). / Kárpáti, Tamás; Veszprémi, Tamás; Thirupathi, Natesan; Liu, Xiaodong; Wang, Zhigang; Ellern, Arkady; Nyulászi, László; Verkade, John G.

In: Journal of the American Chemical Society, Vol. 128, No. 5, 08.02.2006, p. 1500-1512.

Research output: Contribution to journalArticle

Kárpáti, Tamás ; Veszprémi, Tamás ; Thirupathi, Natesan ; Liu, Xiaodong ; Wang, Zhigang ; Ellern, Arkady ; Nyulászi, László ; Verkade, John G. / Synthesis and photoelectron spectroscopic studies of N(CH 2CH2NMe)3P=E (E = O, S, NH, CH2). In: Journal of the American Chemical Society. 2006 ; Vol. 128, No. 5. pp. 1500-1512.
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abstract = "The synthesis and the crystal and molecular structure of N(CH 2CH2NMe)3P=CH2 is reported. The P-Nax distance is rather long in N(CH2CH 2NMe)3P=CH2. The ylide N(CH2CH 2NMe)3P=CH2 proved to be a stronger proton acceptor than proazaphosphatrane N(CH2CH2NMe) 3P, since it was shown to deprotonate N(CH2CH 2NMe)3PH+. The extremely strong basicity of the ylide is in accordance with its low ionization energy (6.3 eV), which is the lowest in the presently investigated series N(CH2CH 2NMe)3P=E (E: CH2, NH, lone pair, O and S), and to the best of our knowledge it is the smallest value observed for a non-conjugated phosphorus ylide. Computations reveal the existence of two bond strech isomers, and the stabilization of the phosphorus centered cation by electron donation from the equatorial and the axial nitrogens. Similar stabilizing effects operate in the case of protonation of E. A fine balance of these different interactions determines the P-Nax distance, which is thus very sensitive to the level of the theory applied. According to the quantum mechanical calculations, methyl substitution at the equatorial nitrogens flattens the pyramidality of this atom, increasing its electron donor capability. As a consequence, the PNax distance in the short-transannular bonded protonated systems and the radical cations is longer by about 0.5 {\AA} in the Neq(Me) than in the Neq(H) systems. Accordingly, isodesmic reaction energies show that a stabilization of about 25 and 10 kcal/mol is attributable to the formation of the transannular bond in case of Neq(H) and the experimentally realizable N eq(Me) species, respectively.",
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T1 - Synthesis and photoelectron spectroscopic studies of N(CH 2CH2NMe)3P=E (E = O, S, NH, CH2)

AU - Kárpáti, Tamás

AU - Veszprémi, Tamás

AU - Thirupathi, Natesan

AU - Liu, Xiaodong

AU - Wang, Zhigang

AU - Ellern, Arkady

AU - Nyulászi, László

AU - Verkade, John G.

PY - 2006/2/8

Y1 - 2006/2/8

N2 - The synthesis and the crystal and molecular structure of N(CH 2CH2NMe)3P=CH2 is reported. The P-Nax distance is rather long in N(CH2CH 2NMe)3P=CH2. The ylide N(CH2CH 2NMe)3P=CH2 proved to be a stronger proton acceptor than proazaphosphatrane N(CH2CH2NMe) 3P, since it was shown to deprotonate N(CH2CH 2NMe)3PH+. The extremely strong basicity of the ylide is in accordance with its low ionization energy (6.3 eV), which is the lowest in the presently investigated series N(CH2CH 2NMe)3P=E (E: CH2, NH, lone pair, O and S), and to the best of our knowledge it is the smallest value observed for a non-conjugated phosphorus ylide. Computations reveal the existence of two bond strech isomers, and the stabilization of the phosphorus centered cation by electron donation from the equatorial and the axial nitrogens. Similar stabilizing effects operate in the case of protonation of E. A fine balance of these different interactions determines the P-Nax distance, which is thus very sensitive to the level of the theory applied. According to the quantum mechanical calculations, methyl substitution at the equatorial nitrogens flattens the pyramidality of this atom, increasing its electron donor capability. As a consequence, the PNax distance in the short-transannular bonded protonated systems and the radical cations is longer by about 0.5 Å in the Neq(Me) than in the Neq(H) systems. Accordingly, isodesmic reaction energies show that a stabilization of about 25 and 10 kcal/mol is attributable to the formation of the transannular bond in case of Neq(H) and the experimentally realizable N eq(Me) species, respectively.

AB - The synthesis and the crystal and molecular structure of N(CH 2CH2NMe)3P=CH2 is reported. The P-Nax distance is rather long in N(CH2CH 2NMe)3P=CH2. The ylide N(CH2CH 2NMe)3P=CH2 proved to be a stronger proton acceptor than proazaphosphatrane N(CH2CH2NMe) 3P, since it was shown to deprotonate N(CH2CH 2NMe)3PH+. The extremely strong basicity of the ylide is in accordance with its low ionization energy (6.3 eV), which is the lowest in the presently investigated series N(CH2CH 2NMe)3P=E (E: CH2, NH, lone pair, O and S), and to the best of our knowledge it is the smallest value observed for a non-conjugated phosphorus ylide. Computations reveal the existence of two bond strech isomers, and the stabilization of the phosphorus centered cation by electron donation from the equatorial and the axial nitrogens. Similar stabilizing effects operate in the case of protonation of E. A fine balance of these different interactions determines the P-Nax distance, which is thus very sensitive to the level of the theory applied. According to the quantum mechanical calculations, methyl substitution at the equatorial nitrogens flattens the pyramidality of this atom, increasing its electron donor capability. As a consequence, the PNax distance in the short-transannular bonded protonated systems and the radical cations is longer by about 0.5 Å in the Neq(Me) than in the Neq(H) systems. Accordingly, isodesmic reaction energies show that a stabilization of about 25 and 10 kcal/mol is attributable to the formation of the transannular bond in case of Neq(H) and the experimentally realizable N eq(Me) species, respectively.

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