Weakening and cleaving N-H bonds is crucial for improving molecular ammonia oxidation catalysts. In this work, we report the synthesis and hydrogen atom abstraction chemistry of bis(ammonia) Cr porphyrin complexes Cr(TPP)(NH3)2 and Cr(TMP)(NH3)2 (TPP = 5,10,15,20-tetraphenyl-meso-porphyrin and TMP = 5,10,15,20-tetramesityl-meso-porphyrin) using bulky aryloxyl radicals. The triple hydrogen atom abstraction reaction results in the formation of CrV(por)(≡N), with the nitride deriving from ammonia, as indicated by UV-Vis and FT-IR spectroscopy, and a single crystal structural determination of Cr(TPP)(≡N). Subsequent oxidation of this chromium(V)-nitrido complex results in the formation of CrIII(por), with scission of the Cr≡N bond. A computational analysis illustrates the progression from CrII to CrV and evaluates the energetics of abstracting hydrogen atoms from CrII-NH3 to generate CrV≡N. The formation and isolation of CrV(por)(≡N) illustrates the stability of these species and the need to chemically activate the nitride moiety for atom transfer or N-N coupling reactivity.
Cook, Brian J., et al. "Weakening the N–H Bonds of NH<sub>3</sub> Ligands: Triple Hydrogen-Atom Abstraction to Form a Chromium(V) Nitride." Inorganic Chemistry, vol. 61, no. 29, Jul. 2022. https://doi.org/10.1021/acs.inorgchem.2c01115
Cook, Brian J., Mosquera, Melissa Barona, Johnson, Samantha J. I., Raugei, Simone, & Bullock, R. Morris (2022). Weakening the N–H Bonds of NH<sub>3</sub> Ligands: Triple Hydrogen-Atom Abstraction to Form a Chromium(V) Nitride. Inorganic Chemistry, 61(29). https://doi.org/10.1021/acs.inorgchem.2c01115
Cook, Brian J., Mosquera, Melissa Barona, Johnson, Samantha J. I., et al., "Weakening the N–H Bonds of NH<sub>3</sub> Ligands: Triple Hydrogen-Atom Abstraction to Form a Chromium(V) Nitride," Inorganic Chemistry 61, no. 29 (2022), https://doi.org/10.1021/acs.inorgchem.2c01115
@article{osti_1887229,
author = {Cook, Brian J. and Mosquera, Melissa Barona and Johnson, Samantha J. I. and Raugei, Simone and Bullock, R. Morris},
title = {Weakening the N–H Bonds of NH<sub>3</sub> Ligands: Triple Hydrogen-Atom Abstraction to Form a Chromium(V) Nitride},
annote = {Weakening and cleaving N-H bonds is crucial for improving molecular ammonia oxidation catalysts. In this work, we report the synthesis and hydrogen atom abstraction chemistry of bis(ammonia) Cr porphyrin complexes Cr(TPP)(NH3)2 and Cr(TMP)(NH3)2 (TPP = 5,10,15,20-tetraphenyl-meso-porphyrin and TMP = 5,10,15,20-tetramesityl-meso-porphyrin) using bulky aryloxyl radicals. The triple hydrogen atom abstraction reaction results in the formation of CrV(por)(≡N), with the nitride deriving from ammonia, as indicated by UV-Vis and FT-IR spectroscopy, and a single crystal structural determination of Cr(TPP)(≡N). Subsequent oxidation of this chromium(V)-nitrido complex results in the formation of CrIII(por), with scission of the Cr≡N bond. A computational analysis illustrates the progression from CrII to CrV and evaluates the energetics of abstracting hydrogen atoms from CrII-NH3 to generate CrV≡N. The formation and isolation of CrV(por)(≡N) illustrates the stability of these species and the need to chemically activate the nitride moiety for atom transfer or N-N coupling reactivity.},
doi = {10.1021/acs.inorgchem.2c01115},
url = {https://www.osti.gov/biblio/1887229},
journal = {Inorganic Chemistry},
issn = {ISSN 0020-1669},
number = {29},
volume = {61},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2022},
month = {07}}