• Title/Summary/Keyword: Pyridyl

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First Example of Monometallic Palladium(II) Compound with Trans-Chelating Tridentate Ligand: Synthesis, Crystal Structure, and Characterizations

  • Tae Hwan Noh
    • Mass Spectrometry Letters
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    • v.14 no.3
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    • pp.110-115
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    • 2023

  • The reaction of (COD)PdCl2 with new C3-symmetric tridentate L (COD = 1,5-cyclooctadien; L = 1,3,5-tris(picolinoyloxyethyl)cyanurate) in a mixture of acetone and dichloromethane produces single crystals consisting of unprecedented monometallacyclic [PdCl2(L)]. This cyclic compound arises from trans-chelation of two of three donating pyridyl groups of L, while the third pyridyl group remains uncoordinated. Electrospray ionization mass spectrometry (ESI-MS) data on L exhibited the major peak corresponding to [C27H24N6O9 + H+]+. Fast atom bombardment mass spectrometry (FABMS) data on [PdCl2(L)], however, showed the mass peak corresponding to the L instead of the present palladium(II) compound species, due to the insolubility and dissociation in solution. The physicochemical properties of the present palladium(II) compound were fully characterized by means of infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, thermal analysis, single-crystal X-ray diffraction (SC-XRD) measurement.

  • https://doi.org/10.5478/MSL.2023.14.3.110 인용 PDF HTML

Aminolysis of Benzyl 4-Pyridyl Carbonate in Acetonitrile: Effect of Modification of Leaving Group from 2-Pyridyloxide to 4-Pyridyloxide on Reactivity and Reaction Mechanism

  • Bae, Ae-Ri;Um, Ik-Hwan
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2719-2723
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    • 2012

  • A kinetic study is reported for nucleophilic substitution reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in MeCN. The plot of pseudo-first-order rate constant ($k_{obsd}$) vs. [amine] curves upward, which is typical for reactions reported previously to proceed through a stepwise mechanism with two intermediates (i.e., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). Dissection of $k_{obsd}$ into the second- and third-order rate constants (i.e., $Kk_2$ and $Kk_3$, respectively) reveals that $Kk_3$ is significantly larger than $Kk_2$, indicating that the reactions proceed mainly through the deprotonation pathway (i.e., the $k_3$ process) in a high [amine] region. This contrasts to the recent report that the corresponding aminolysis of benzyl 2-pyridyl carbonate 5 proceeds through a forced concerted mechanism. An intramolecular H-bonding interaction was suggested to force the reactions of 5 to proceed through a concerted mechanism, since it could accelerate the rate of leaving-group expulsion (i.e., an increase in $k_2$). However, such H-bonding interaction, which could increase $k_2$, is structurally impossible for the reactions of 6. Thus, presence or absence of an intramolecular H-bonding interaction has been suggested to be responsible for the contrasting reaction mechanisms (i.e., a forced concerted mechanism for the reaction of 5 vs. a stepwise mechanism with $T^{\pm}$ and $T^-$ as intermediates for that of 6).

  • https://doi.org/10.5012/bkcs.2012.33.8.2719 인용 PDF KSCI