Electronic Structures and Reactivity Profiles of Aryl Nitrenoid-Bridged Dicopper Complexes

Dicopper complexes templated by dinucleating, pacman dipyrrin ligand scaffolds ((Mes)dmx, (tBu)dmx: dimethylxanthine-bridged, cofacial bis-dipyrrin) were synthesized by deprotonation/metalation with mesitylcopper (CuMes; Mes: mesityl) or by transmetalation with cuprous precursors from the correspond...

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Published in:Journal of the American Chemical Society Vol. 142; no. 5; pp. 2264 - 2276
Main Authors: Carsch, Kurtis M., Lukens, James T., DiMucci, Ida M., Iovan, Diana A., Zheng, Shao-Liang, Lancaster, Kyle M., Betley, Theodore A.
Format: Journal Article
Language:English
Published: WASHINGTON Amer Chemical Soc 05.02.2020
Subjects:
Chemistry
Chemistry, Multidisciplinary
Copper - chemistry
Imines - chemistry
Models, Molecular
Molecular Structure
Oxidation-Reduction
Physical Sciences
Science & Technology
X-Ray Absorption Spectroscopy
IMIDO COMPLEXES
OXIDATION
AMINATION
METHANE
TRANSITION-METAL-COMPLEXES
GROUND-STATE
DIAMOND CORES
CU-A
COPPER
H BOND FUNCTIONALIZATION
ISSN:0002-7863, 1520-5126, 1520-5126
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Summary:Dicopper complexes templated by dinucleating, pacman dipyrrin ligand scaffolds ((Mes)dmx, (tBu)dmx: dimethylxanthine-bridged, cofacial bis-dipyrrin) were synthesized by deprotonation/metalation with mesitylcopper (CuMes; Mes: mesityl) or by transmetalation with cuprous precursors from the corresponding deprotonated ligand. Neutral imide complexes ((R)dmx)Cu-2(mu(2)-NAr) (R: Mes, Bu-t; Ar: 4-MeOC6H4, 3,5-(F3C),C6H3) were synthesized by treatment of the corresponding dicuprous complexes with aryl azides. While one-electron reduction of ((Mes)dmx)Cu-2(mu(2)-N(C6H4OMe)) with potassium graphite initiates an intramolecular, benzylic C-H amination at room temperature, chemical reduction of ((tBu)dmx)Cu-2(mu(2)-NAr) leads to isolable [((tBu)dmx)Cu-2(mu(2)-NAr)](-) product salts. The electronic structures of the thermally robust [((tBu)dmx)Cu-2(mu(2)-NAr)](0/-) complexes were assessed by variable-temperature electron paramagnetic resonance spectroscopy, X-ray absorption spectroscopy (Cu L-2,L-3/K-edge, N K-edge), optical spectroscopy, and DFT/CASSCF calculations. These data indicate that the formally Class IIIA mixed valence complexes of the type [((R)dmx)Cu-2(mu(2)-NAr)](-) feature significant NAr-localized spin following reduction from electronic population of the [Cu-2(mu(2)-NAr)] pi* manifold, contrasting previous methods for engendering iminyl character through chemical oxidation. The reactivity of the isolable imido and iminyl complexes are examined for prototypical radical-promoted reactivity (e.g., nitrene transfer and H-atom abstraction), where the divergent reactivity is rationalized by the relative degree of N-radical character afforded from different aryl substituents.
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ISSN:0002-7863
1520-5126
1520-5126
DOI:10.1021/jacs.9b09616