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McCarthy SM, Lin YC, Devarajan D, et al. Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism. J Am Chem Soc. 2014;136(12):4640-50doi: 10.1021/ja412469e.
McCarthy, S. M., Lin, Y. C., Devarajan, D., Chang, J. W., Yennawar, H. P., Rioux, R. M., Ess, D. H., & Radosevich, A. T. (2014). Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism. Journal of the American Chemical Society, 136(12), 4640-50. https://doi.org/10.1021/ja412469e
McCarthy, Sean M, et al. "Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism." Journal of the American Chemical Society vol. 136,12 (2014): 4640-50. doi: https://doi.org/10.1021/ja412469e
McCarthy SM, Lin YC, Devarajan D, Chang JW, Yennawar HP, Rioux RM, Ess DH, Radosevich AT. Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism. J Am Chem Soc. 2014 Mar 26;136(12):4640-50. doi: 10.1021/ja412469e. Epub 2014 Mar 17. PMID: 24597970.
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J Am Chem Soc. 2014 Mar 26;136(12):4640-50. doi: 10.1021/ja412469e. Epub 2014 Mar 17.

Intermolecular N-H oxidative addition of ammonia, alkylamines, and arylamines to a planar σ(3)-phosphorus compound via an entropy-controlled electrophilic mechanism.

Journal of the American Chemical Society

Sean M McCarthy, Yi-Chun Lin, Deepa Devarajan, Ji Woong Chang, Hemant P Yennawar, Robert M Rioux, Daniel H Ess, Alexander T Radosevich

Affiliations

  1. Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.

PMID: 24597970 DOI: 10.1021/ja412469e

Abstract

Ammonia, alkyl amines, and aryl amines are found to undergo rapid intermolecular N-H oxidative addition to a planar mononuclear σ(3)-phosphorus compound (1). The pentacoordinate phosphorane products (1·[H][NHR]) are structurally robust, permitting full characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Isothermal titration calorimetry was employed to quantify the enthalpy of the N-H oxidative addition of n-propylamine to 1 ((n)PrNH2 + 1 → 1·[H][NH(n)Pr], ΔHrxn(298) = -10.6 kcal/mol). The kinetics of n-propylamine N-H oxidative addition were monitored by in situ UV absorption spectroscopy and determination of the rate law showed an unusually large molecularity (ν = k[1][(n)PrNH2](3)). Kinetic experiments conducted over the temperature range of 10-70 °C revealed that the reaction rate decreased with increasing temperature. Activation parameters extracted from an Eyring analysis (ΔH(⧧) = -0.8 ± 0.4 kcal/mol, ΔS(⧧) = -72 ± 2 cal/(mol·K)) indicate that the cleavage of strong N-H bonds by 1 is entropy controlled due to a highly ordered, high molecularity transition state. Density functional calculations indicate that a concerted oxidative addition via a classical three-center transition structure is energetically inaccessible. Rather, a stepwise heterolytic pathway is preferred, proceeding by initial amine-assisted N-H heterolysis upon complexation to the electrophilic phosphorus center followed by rate-controlling N → P proton transfer.

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