Odd-electron bonds have unique electronic structures and are often encountered as transiently stable, homonuclear species. In this study, a pair of copper complexes supported by Group 13 metalloligands, M[N((o-C6H4)NCH2PiPr2)3] (M = Al or Ga), featuring two-center/one-electron (2c/1e) σ-bonds were synthesized by one-electron reduction of the corresponding Cu(i) ⇢ M(III) counterparts. The copper bimetallic complexes were investigated by X-ray diffraction, cyclic voltammetry, electron paramagnetic spectroscopy, and density functional theory calculations. The combined experimental and theoretical data corroborate that the unpaired spin is delocalized across Cu, M, and ancillary atoms, and the singly occupied molecular orbital (SOMO) corresponds to a σ-(Cu-M) bond involving the Cu 4pz and M ns/npz atomic orbitals. Collectively, the data suggest the covalent nature of these interactions, which represent the first examples of odd-electron σ-bonds for the heavier Group 13 elements Al and Ga.
Bibliographical noteFunding Information:
This work is dedicated to Professor John E. Ellis on the occasion of his 79th birthday. The authors thank Prof. John Lipscomb and Melanie Rogers for access to the EPR spectrometer and Dr James T. Moore for collection of EPR data. The experimental and computational work was supported by the NSF (CHE-1954751 and CHE-2054723). TRS was supported by a NSF graduate fellowship. X-ray diffraction experiments were performed using a crystal diffractometer acquired through an NSF-MRI award (CHE-1229400). The computational resources were provided by the Minnesota Supercomputing Institute (MSI) at the University of Minnesota and the Chicago Center for Theoretical Chemistry (CCTCh) at the University of Chicago.
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