title: Switching the Spin State of Diphenylcarbene via Halogen Bonding.
abstract: The interactions between diphenylcarbene DPC and the halogen bond donors CF3I and CF3Br were investigated using matrix isolation spectroscopy (IR, UV-vis, and EPR) in combination with QM and QM/MM calculations. Both halogen bond donors CF3X form very strong complexes with the singlet state of DPC, but only weakly interact with triplet DPC. This results in a switching of the spin state of DPC, the singlet complexes becoming more stable than the triplet complexes. CF3I forms a second complex (type II) with DPC that is thermodynamically slightly more stable. Calculations predict that in this second complex the DPC···I distance is shorter than the F3C···I distance, whereas in the first (type I) complex the DPC···I distance is, as expected, longer. CF3Br only forms the type I complex. Upon irradiation I or Br, respectively, are transferred to the DPC carbene center and radical pairs are formed. Finally, on annealing, the formal C-X insertion product of DPC is observed. Thus, halogen bonding is a powerful new principle to control the spin state of reactive carbenes.
authors.affiliation: Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , 44801 Bochum, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Henkel
authors.affiliation: Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , 44801 Bochum, Germany.
authors.forename: Paolo
authors.initials: P
authors.lastname: Costa
authors.affiliation: Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , 44801 Bochum, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Klute
authors.affiliation: Max-Planck-Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany.
authors.forename: Pandian
authors.initials: P
authors.lastname: Sokkar
authors.affiliation: Max-Planck-Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany.
authors.forename: Miguel
authors.initials: M
authors.lastname: Fernandez-Oliva
authors.affiliation: Max-Planck-Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
authors.affiliation: Max-Planck-Institut für Kohlenforschung , 45470 Mülheim an der Ruhr, Germany.
authors.forename: Elsa
authors.initials: E
authors.lastname: Sanchez-Garcia
authors.affiliation: Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , 44801 Bochum, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Sander