Research

Our research is located in the field of physical-organic chemistry and focuses on reactive intermediates in the broadest sense. The employed methodology used is characterized by an interplay of modern organic synthesis, computational quantum chemistry, and cryogenic matrix isolation spectroscopy. Our primary goal is the detailed spectroscopic and structural characterization of unusual intermediates and their utilization in difficult to achieve organic transformations, including the activation of small molecules (H₂, O₂, SO, CO₂, N₂O, SF₆, etc.).

 σ⁰π²-Carbenes: Activation of Small Molecules

In addition to the two well-known electron configurations (σ²π⁰-singlet and σ¹π¹-triplet), carbenes can also exhibit a singlet ground state in which the free electron pair is located in the π system while the σ orbital remains vacant. This unusual electron configuration can be favored if the carbenic electron pair is incorporated into an aromatic sextet and the unoccupied σ orbital is energetically raised by interactions with neighboring free electron pairs in the molecular plane.^[1] Accordingly, Hoffmann and Borden proposed that the experimentally known 2H-imidazol-2-ylidene 1 is such a σ⁰π² ground-state carbene and not, as previously assumed, a strained, planar carbodiimide.^[1,2] In our previous work, we have already shown that the carbene circumvents the usual non-least-motion reactivity^[3] in its reactions with double bonds and H₂ as well as the carbenic spin selectivity in the addition of molecular triplet oxygen.^[4] A general goal of our research, in addition to developing new structural motifs,^[5] is the utilization of these highly electrophilic carbenes towards the activation of small molecules.

[1]          B. Chen, A. Y. Rogachev, D. A. Hrovat, R. Hoffmann, W. T. Borden, J. Am. Chem. Soc. 2013, 135, 13954-13964.
[2]          G. Maier, J. Endres, Chem. - Eur. J. 1999, 5, 1590-1597.
[3]          S. F. Clewing, J. P. Wagner, J. Org. Chem. 2021, 86, 15247-15252.
[4]          J. P. Wagner, J. Am. Chem. Soc. 2022, 144, 5937-5944.
[5]          J. P. Wagner, Chem. Commun. 2024, 60, 3327-3330.