We thank Prof. W. Kirmse for valuable discussions. This work was supported by the Cluster of Excellence RESOLV (EXC 1069) funded by the Deutsche Forschungsgemeinschaft.
Hydrogen Bonding Switches the Spin State of Diphenylcarbene from Triplet to Singlet†
Article first published online: 2 APR 2014
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Volume 126, Issue 20, pages 5222–5225, May 12, 2014
How to Cite
Costa, P. and Sander, W. (2014), Hydrogen Bonding Switches the Spin State of Diphenylcarbene from Triplet to Singlet. Angew. Chem., 126: 5222–5225. doi: 10.1002/ange.201400176
- Issue published online: 8 MAY 2014
- Article first published online: 2 APR 2014
- Manuscript Received: 7 JAN 2014
- Deutsche Forschungsgemeinschaft
Spin specificity is one of the most important properties of carbenes in their reactions. Alcohols are typically used to probe the reactive spin states of carbenes: OH insertions are assumed to be characteristic of singlet states, whereas CH insertions are typical for the triplets. Surprisingly, the experiments presented here suggest that the spin ground state of diphenylcarbene 1 switches from triplet to singlet if the carbene is allowed to interact with methanol. Carbene 1 and methanol form a strongly hydrogen-bonded singlet ground state complex that was synthesized in low-temperature matrices and characterized by IR spectroscopy. This methanol complex is only metastable, and even at 3 K slowly rearranges to form the product of OH insertion through quantum chemical tunneling. Thus, the ground state triplet (in the gas phase) carbene 1 forms exclusively the products expected from a singlet carbene. Whereas the assumption of spin specific reactions of carbenes is correct, the spin state itself can be changed by solvent interactions, and therefore widely accepted conclusions drawn from earlier experiments have to be revisited.