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Title: Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2H 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); Energy Frontier Research Centers (EFRC) (United States). Center for Molecular Electrocatalysis (CME)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1439667
Report Number(s):
PNNL-SA-129950
Journal ID: ISSN 0002-7863; KC0307010
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 140; Journal Issue: 7
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 N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 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 N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 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 N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 Macrocycle". United States. doi:10.1021/jacs.7b11132.
@article{osti_1439667,
title = {Catalytic Silylation of N2 and Synthesis of NH3 and N2H4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P4 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},
number = 7,
volume = 140,
place = {United States},
year = {Wed Feb 07 00:00:00 EST 2018},
month = {Wed Feb 07 00:00:00 EST 2018}
}