title: A terminal, fluxional η4-benzene complex with a thermally accessible triplet state is the primary photoproduct in the intercyclobutadiene haptotropism of (CpCo)phenylenes.
abstract: Low-temperature irradiation of linear [3]- and [4]phenylene cyclopentadienylcobalt complexes generates labile, fluxional η(4)-arene complexes, in which the metal resides on the terminal ring. Warming induces a haptotropic shift to the neighboring cyclobutadiene rings, followed by the previously reported intercyclobutadiene migration. NMR scrutiny of the primary photoproduct reveals a thermally accessible 16-electron cobalt η(2)-triplet species, which, according to DFT computations, is responsible for the rapid symmetrization of the molecules along their long axes. Calculations indicate that the entire haptotropic manifold along the phenylene frame is governed by dual-state reactivity of alternating 18-electron singlets and 16-electron triplets.
authors: Department of Chemistry, University of Houston, Houston, TX 77204-5003 (USA).
authors: Thomas A
authors: TA
authors: Albright
authors: Rima
authors: R
authors: Drissi
authors: Vincent
authors: V
authors: Gandon
authors: Sander
authors: S
authors: Oldenhof
authors: Oluwakemi A
authors: OA
authors: Oloba-Whenu
authors: Robin
authors: R
authors: Padilla
authors: Hao
authors: H
authors: Shen
authors: K Peter C
authors: KP
authors: Vollhardt
authors: Vincent
authors: V
authors: Vreeken
keywords: ab initio calculations; arene ligands; haptotropism; isomerization; photochemistry