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Metal-centred planar [15]annulenes

Nature volume 641, pages 106–111 (2025)Cite this article

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Abstract

The discovery of ferrocene1 heralded the advent of modern organometallic chemistry. Characterized by the π-coordination of a metal by one or two planar annulene anions, ferrocenes and their analogues2,3,4 exemplify the archetype of out-of-plane annulene metal complexes. By contrast, the integration of metal within the annulene core to form in-plane annulene metal complexes featuring metal–carbon σ bonds has been obstructed not only by the synthetic difficulty and the non-planarity of annulenes with appropriate internal dimensions, but also by the difficulty of embedding the metal. These challenges have prevented the isolation of such in-plane annulene metal complexes. Here we report the preparation of three metal-centred planar [15]annulene frameworks. The most symmetrical fragment has D5h symmetry, with the metal centre shared by five identical five-membered rings. Density functional theory calculations demonstrate that metal d orbitals participate in conjugation with these five-membered rings, rendering all of them aromatic. The overall framework bears a loose structural and spectroscopic analogy to metallo-expanded porphyrins with multiple aza donors5, which thus provides a nexus between annulene chemistry and classic heteroatom-based coordination chemistry. The present systems display high stability and are easily functionalized. We thus suggest that metal-centred planar annulenes could emerge as promising building blocks for materials science.

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Fig. 1: Coordination chemistry of annulenes, porphyrin and related compounds.
Fig. 2: Synthesis and characterization of metal-centred planar [15]annulenes.
Fig. 3: Theoretical analysis of 5a′.
Fig. 4: Post-functionalization of 5a and 4a.

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Data availability

All the data needed to evaluate the conclusions in this work are present in the article or Supplementary Information. Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2374570 (2c), 2374585 (3b), 2374576 (4a), 2374580 (4b), 2374584 (4c), 2374575 (5a), 2374581 (5b), 2374579 (7), 2374582 (8) and 2392762 (10). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (grant nos. 92156021, 22350009, 21931002, 22371111 and 22071098), the Guangdong Provincial Key Laboratory of Catalysis (grant no. 2020B121201002), Introduction of Major Talent Projects in Guangdong Province (grant no. 2019CX01C079), Guangdong Grants (grant no. 2021ZT09C064), High Level of Special Funds (G03050K003), the Postdoctoral Fellowship Program of CPSF (GZB20240287) and the Outstanding Talents Training Fund in Shenzhen. The work in Austin was supported by the National Science Foundation (CHE-2304731 to J.L.S.) with further support provided by the Robert A. Welch Foundation (F-0018). The theoretical work was supported by the Center for Computational Science and Engineering at SUSTech. We thank J. Li of Tsinghua University, L. L. Liu, X. Jiang, X. Chang and Z. Dong of Southern University of Science and Technology, and H. Li of Zhejiang University for providing helpful suggestions in preparing the manuscript.

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Author notes

  1. These authors contributed equally: Binbin Xu, Dafa Chen, Kaidong Ruan, Ming Luo

Authors and Affiliations

  1. Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis, Department of Chemistry, Southern University of Science and Technology, Shenzhen, China

    Binbin Xu, Dafa Chen, Kaidong Ruan, Ming Luo, Yuanting Cai, Jia Qiu, Wenhao Zhou, Bula Cao & Haiping Xia

  2. Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong, China

    Zhenyang Lin

  3. Department of Chemistry, The University of Texas at Austin, Austin, TX, USA

    Jonathan L. Sessler

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Contributions

D.C. and H.X. devised the project and supervised the experimental study. B.X., J.L.S. and H.X. analysed the experimental data. B.X., K.R., Y.C., J.Q., W.Z. and B.C. performed the experimental work. K.R., M.L. and Z.L. performed the computational analyses. B.X., D.C., K.R., M.L., J.L.S. and H.X. wrote the paper and prepared the supplementary information with input from all authors. All authors discussed the results in detail and commented on the manuscript.

Corresponding author

Correspondence to Haiping Xia.

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The authors declare no competing interests.

Peer review

Peer review information

Nature thanks Fabrizio Ortu, Miquel Solà and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Supplementary information

Supplementary Information

Supplementary methods, characterization details, optimized Cartesian coordinates, Figs. 1–160, Tables 1–24 and references.

Crystallographic Data

Crystallographic data for complexes 2c, 2d, 3b, 4a, 4b, 4c, 5a, 5b, 7, 8 and 10.

Peer Review File

Supplementary Video 1

Simulation of the gauge-including magnetically induced current (GIMIC) in the [55555] metallo-annulene model 5a′. This video shows the diatropic ring currents of 5a′, and suggests the [55555] metallo-annulene skeleton is aromatic.

Supplementary Video 2

Simulation of the gauge-including magnetically induced current (GIMIC) in benzene. This video shows the diatropic ring currents, and suggests benzene is aromatic.

Supplementary Video 3

Simulation of the gauge-including magnetically induced current (GIMIC) in the [55753] metallo-annulene model 2a′. This video shows the diatropic ring currents of 2a′, and suggests the [55753] metallo-annulene skeleton is aromatic.

Supplementary Video 4

Simulation of the gauge-including magnetically induced current (GIMIC) in the [55735] metallo-annulene model 3a′. This video shows the diatropic ring currents of 3a′, and suggests the [55735] metallo-annulene skeleton is aromatic.

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Xu, B., Chen, D., Ruan, K. et al. Metal-centred planar [15]annulenes. Nature 641, 106–111 (2025). https://doi.org/10.1038/s41586-025-08841-2

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