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Contributed by Chi-Ming Che, November 10, 2020 (sent for review September 14, 2020; reviewed by Garnet Chan, Stephen Hashmi, Zhenyang Lin, and Ricardo Mata)
Significance
Metallophilicity is widely regarded as a driving force in the self-assembly of closed-shell d8 and d10 metal complexes. The self-assembled metal complexes have applications in organic semiconductors, biosensing, organic light-emitting diodes, and photocatalysis. The attractive metallophilicity in the ground state is believed to originate from spd orbital hybridization or electron correlation interaction strengthened by relativistic effect. These two models have remained controversial for a long time. Our findings conclude that the M–M′ closed-shell interaction is repulsive due to strong M–M′ Pauli repulsion strengthened by (n + 1)s-nd orbital hybridization and relativistic effect. The M–M′ repulsion is counterbalanced by the ligand–ligand dispersion and electrostatic interaction, leading to a close unsupported M–M′ distance.
Abstract
Metallophilicity is defined as the interaction among closed-shell metal centers, the origin of which remains controversial, particularly for the roles of spd orbital hybridization (mixing of the spd atomic orbitals of the metal atom in the molecular orbitals of metal complex) and the relativistic effect. Our studies reveal that at close M–M′ distances in the X-ray crystal structures of d8 and d10 organometallic complexes, M–M′ closed-shell interactions are repulsive in nature due to strong M–M′ Pauli repulsion. The relativistic effect facilitates (n + 1)s-nd and (n + 1)p-nd orbital hybridization of the metal atom, where (n + 1)s-nd hybridization induces strong M–M′ Pauli repulsion and repulsive M–M′ orbital interaction, and (n + 1)p-nd hybridization suppresses M–M′ Pauli repulsion. This model is validated by both DFT (density functional theory) and high-level coupled-cluster singles and doubles with perturbative triples computations and is used to account for the fact that the intermolecular or intramolecular Ag–Ag′ distance is shorter than the Au–Au′ distance, where a weaker Ag–Ag′ Pauli repulsion plays an important role. The experimental studies verify the importance of ligands in intermolecular interactions. Although the M–M′ interaction is repulsive in nature, the linear coordination geometry of the d10 metal complex suppresses the L–L′ (ligand–ligand) Pauli repulsion while retaining the strength of the attractive L–L′ dispersion, leading to a close unsupported M–M′ distance that is shorter than the sum of the van der Waals radius (rvdw) of the metal atoms.
Footnotes
- ↵1To whom correspondence may be addressed. Email: wendyqyw{at}hku.hk, juny{at}hku.hk, or cmche{at}hku.hk.
Author contributions: Q.W. and C.-M.C. designed research; Q.W., J.Y., and W.-P.T. performed research; Q.W., J.Y., and C.-M.C. analyzed data; and Q.W., J.Y., and C.-M.C. wrote the paper.
Reviewers: G.C., California Institute of Technology; S.H., University of Heidelberg; Z.L., The Hong Kong University of Science and Technology; and R.M., University of Göttingen.
The authors declare no competing interest.
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2019265118/-/DCSupplemental.
Data Availability.
All study data are included in the article and SI Appendix.
Published under the PNAS license.
References
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Strong metal–metal Pauli repulsion leads to repulsive metallophilicity in closed-shell d8 and d10 organometallic complexes
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- Physical Sciences
- Chemistry
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