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Triplet carbenes with transition-metal substituents

Nature Chemistry (2024)Cite this article

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Abstract

The extraordinary advances in carbene (R1–C–R2) chemistry have been fuelled by strategies to stabilize the electronic singlet state via π interactions. In contrast, the lack of similarly efficient approaches to obtain authentic triplet carbenes with appreciable lifetimes beyond cryogenic temperatures hampers their exploitation in synthesis and catalysis. Transition-metal substitution represents a potential strategy, but metallocarbenes (M–C–R) usually represent high-lying excited electronic configurations of the well-established carbyne complexes (M≡C–R). Here we report the synthesis and characterization of triplet metallocarbenes (M–C–SiMe3, M = PdII, PtII) that are persistent beyond cryogenic conditions, and their selective reactivity towards carbene C–H insertion and carbonylation. Bond analysis reveals significant stabilization by spin-polarized push–pull interactions along both π-bonding planes, which fundamentally differs from bonding in push–pull singlet carbenes. This bonding model, thus, expands key strategies for stabilizing the open-shell carbene electromers and closes a conceptual gap towards carbyne complexes.

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Fig. 1: Chemical strategies for the stabilization of singlet versus triplet carbenes.
Fig. 2: Photochemical reactivity of the diazoalkyl complexes.
Fig. 3: Experimental electronic structure characterization.
Fig. 4: Photochemical crystal-to-crystal conversion experiments.
Fig. 5: Quantum-chemical electronic structure characterization of 5a.

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Data availability

All data generated and analysed during this study are included in this article and its Supplementary Information or are available from the corresponding authors upon reasonable request. The spectroscopic, magnetic and computational source data have been deposited in the data repository of the Göttingen research alliance (GRO.data) and can be retrieved at https://doi.org/10.25625/DIE64H. Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2320937 (1a), 2320938 (1b), 2320939 (2a), 2320940 (2b), 2320941 (3), 2320942 (4), 2320943 (5a), 2320944 (5b), 2320945 (2b′) and 2320946 (6). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.

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Acknowledgements

S.S. thanks the Deutsche Forschungsgemeinschaft for support (Priority Program 2102, grant SCHN950/6-2). Z.-J.L. is grateful to the Alexander von Humboldt Foundation for a postdoctoral financial support and D.-J. Hong for help with X-ray crystallography. P. D. Engel and N. Wegerich are acknowledged for support of the quantum-chemical study. Quantum-chemical calculations were performed at the Center for Scientific Computing (CSC) Frankfurt on the Goethe and Fuchs high-performance computer clusters. The SQUID magnetometer was funded by the Deutsche Forschungsgemeinschaft (DFG, project number INST 186/1329-1 FUGG) and the Niedersächsisches Ministerium für Wissenschaft und Kultur.

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Author notes

  1. These authors contributed equally: Ze-Jie Lv, Kim A. Eisenlohr.

Authors and Affiliations

  1. Institut für Anorganische Chemie and International Center for Advanced Studies of Energy Conversion (ICASEC), Universität Göttingen, Göttingen, Germany

    Ze-Jie Lv, Serhiy Demeshko, Regine Herbst-Irmer & Sven Schneider

  2. Institut für Anorganische und Analytische Chemie, Goethe-Universität, Frankfurt am Main, Germany

    Kim A. Eisenlohr, Hendrik Verplancke & Max C. Holthausen

  3. Department of Chemistry, Johannes Gutenberg University, Mainz, Germany

    Robert Naumann, Thomas Reuter & Katja Heinze

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Contributions

Z.-J.L., M.C.H. and S.S. conceived the work and designed the experiments. S.S. supervised the experimental study, and M.C.H supervised the quantum-chemical study. Z.-J.L. performed synthetic, spectroscopic and X-ray crystallographic work. Z.-J.L. and R.H.-I. performed the crystallographic data analyses. K.A.E. performed the computational work with support of H.V. for the ZFS computations. S.D. carried out the magnetic characterization. R.N. and T.R. carried out the low-temperature UV–vis spectroscopy supervised by K.H. All authors discussed the results in detail and commented on the manuscript.

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Correspondence to Max C. Holthausen or Sven Schneider.

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Nature Chemistry thanks Liang Deng, William Lewis and David Wilson for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Detailed descriptions of experimental, spectroscopic, crystallographic and quantum-chemical methods and results.

Supplementary Data 1

Crystallographic data for 1a (CCDC 2320937).

Supplementary Data 2

Crystallographic data for 1b (CCDC 2320938).

Supplementary Data 3

Crystallographic data for 2a (CCDC 2320939).

Supplementary Data 4

Crystallographic data for 2b (CCDC 2320940).

Supplementary Data 5

Crystallographic data for 2b’ (CCDC 2320945).

Supplementary Data 6

Crystallographic data for 3 (CCDC 2320941).

Supplementary Data 7

Crystallographic data for 4 (CCDC 2320942).

Supplementary Data 8

Crystallographic data for 5a (CCDC 2320943).

Supplementary Data 9

Crystallographic data for 5b (CCDC 2320944).

Supplementary Data 10

Crystallographic data for 6 (CCDC 2320946).

Supplementary Data 11

Computational optimized coordinates.

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Lv, ZJ., Eisenlohr, K.A., Naumann, R. et al. Triplet carbenes with transition-metal substituents. Nat. Chem. (2024). https://doi.org/10.1038/s41557-024-01597-8

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