Metalla-aromatics: Planar, Nonplanar, and Spiro
Yongliang Zhang1, Chao Yu1, Zhe Huang1
1Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
Accounts of Chemical Research
|April 14, 2021
Summary
Researchers have synthesized novel metalla-aromatics, challenging traditional aromaticity rules. These compounds exhibit unique planar, nonplanar, and spiro geometries involving transition metals, expanding the understanding of aromatic systems.
Area of Science:
- Organometallic Chemistry
- Aromaticity Studies
- Synthetic Chemistry
Background:
- Aromaticity is a fundamental chemical concept, typically requiring planarity.
- Transition metals in conjugated systems (metalla-aromatics) can exhibit non-traditional geometries.
- Previous understanding of metalla-aromatic structures was limited.
Purpose of the Study:
- To explore and synthesize unprecedented types of metalla-aromatic compounds.
- To investigate the role of transition metals in non-planar and spiro aromatic systems.
- To expand the understanding of aromaticity beyond traditional planar requirements.
Main Methods:
- Reaction of 1,4-dilithio-1,3-butadienes with low-valent transition-metal complexes.
- Synthesis of monocyclic, spiro, nonplanar, and ferrocene-analogue metalla-aromatics.
- Utilizing unique behaviors of dilithio reagents and transition metal properties.
Main Results:
- Nearly planar dicupra[10]annulenes with bridging copper atoms.
- Four types of spiro metalla-aromatics with diverse geometries and aromatic systems (10π, 40π Craig-Möbius, 6π).
- Nonplanar butadienyl diiron complexes with σ-type orbital overlap for aromaticity.
- Dinickelaferrocene, a ferrocene analogue, exhibiting aromaticity through metal-ligand electron back-donation.
Conclusions:
- Metalla-aromatics can adopt nonplanar and spiro geometries, challenging the planarity prerequisite for aromaticity.
- The involvement of transition metals significantly diversifies aromatic system structures and bonding.
- These findings open avenues for novel chemical bonding, reactivity, and functional applications of metalla-aromatics.
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