Abstract
Tripodal ligands that can encapsulate single or multiple metal sites in C3-symmetric geometric configurations constitute valuable targets for novel catalysts. Of particular interest in ligand development are efforts toward incorporating apical elements that exhibit little if any electron donicity, to enhance the electrophilic nature of a trans positioned active oxidant (e.g., metal-oxo, -nitrene). The tripodal ligand TMG3trphen-Arene has been synthesized, featuring an arene platform 1,3,5-substituted with phenylene arms possessing tetramethylguanidinyl (TMG) residues. Compound [(TMG3trphen-Arene) Cu3(μ-Cl)3] has been subsequently synthesized by extracting a Cu3(μ-Cl)3 cluster from anhydrous CuCl and shown to encapsulate a crown-shaped Cu3(μ-Cl)3 fragment, supported by Cu-NTMG bonds and modest Cu3⋯arene long-range contacts. Energy decomposition analysis (EDA) indicates that electrostatic contributions to the total interaction energy far exceed those due to orbital interactions. The latter involve orbital pairings largely associated with the NTMG stabilization of the Cu3(μ-Cl)3 cluster. The independent gradient model based on the Hirshfeld partition (IGMH) corroborates that contacts between the arene platform and the Cu3 triangle are noncovalent in nature. Catalyst [(TMG3trphen-Arene) Cu3(μ-Cl)3] enables amination of sec-benzylic and tert-C-H bonds of a panel of substrates by pre-synthesized PhINTces in solvent matrices that incorporate small amounts of HFIP. The involvement of an electrophilic aminating agent is evidenced by the better yields obtained for electron-rich benzylic sites and is further supported by Hammett analysis that reveals the development of a small positive charge during C-H bond activation. A rather modest KIE effect (2.1) is obtained from intramolecular H(D) competition in the amination of ethylbenzene, at the borderline of reported values for concerted and stepwise C-H amination systems. DFT analysis of the putative copper-nitrene oxidant indicates that the nitrene N atom is bridging between two copper sites in closely spaced triplet (ground state) and broken-symmetry singlet electronic configurations.
Recommended Citation
M. Sharma et al., "C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand Scaffold Featuring an Arene Platform and Tetramethylguanidinyl Residues," Dalton Transactions, vol. 53, no. 38, pp. 15946 - 15958, Royal Society of Chemistry, Sep 2024.
The definitive version is available at https://doi.org/10.1039/d4dt01670j
Department(s)
Chemistry
International Standard Serial Number (ISSN)
1477-9234; 1477-9226
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2024 Royal Society of Chemistry, All rights reserved.
Publication Date
06 Sep 2024
PubMed ID
39264342
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 2.txt (44 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 3.txt (1 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 4.txt (1 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 5.pdf (1642 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 6.pdf (6394 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 7.txt (8 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 8.txt (1 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 9.txt (1 kB)
C-H Amination Chemistry Mediated by Trinuclear Cu(I) Sites Supported by a Ligand______Supplemental File 10.txt (5 kB)
Comments
National Institutes of Health, Grant R15GM117508