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Title: Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle

Abstract

We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] P4Cr(N2)2, bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons. For example, the reaction of cobaltocene (CoCp2) and collidinium triflate (ColH[OTf]) at room temperature to afforded 1.9 equiv of NH3, or at -78 °C to afforded a mixture of NH3 and N2H4; (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH, (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford a 1.4 equiv of 15NH3.

Authors:
 [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1508294
Report Number(s):
PNNL-SA-129950
Journal ID: ISSN 0002-7863
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 7; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

Citation Formats

Kendall, Alexander J., Johnson, Samantha I., Bullock, R. Morris, and Mock, Michael T. Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle. United States: N. p., 2018. Web. doi:10.1021/jacs.7b11132.
Kendall, Alexander J., Johnson, Samantha I., Bullock, R. Morris, & Mock, Michael T. Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle. United States. doi:10.1021/jacs.7b11132.
Kendall, Alexander J., Johnson, Samantha I., Bullock, R. Morris, and Mock, Michael T. Wed . "Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle". United States. doi:10.1021/jacs.7b11132.
@article{osti_1508294,
title = {Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2 H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle},
author = {Kendall, Alexander J. and Johnson, Samantha I. and Bullock, R. Morris and Mock, Michael T.},
abstractNote = {We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] P4Cr(N2)2, bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons. For example, the reaction of cobaltocene (CoCp2) and collidinium triflate (ColH[OTf]) at room temperature to afforded 1.9 equiv of NH3, or at -78 °C to afforded a mixture of NH3 and N2H4; (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH, (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford a 1.4 equiv of 15NH3.},
doi = {10.1021/jacs.7b11132},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 7,
volume = 140,
place = {United States},
year = {2018},
month = {2}
}