A Terminal,Fluxional η4‐Benzene Complex with a Thermally Accessible Triplet State is the Primary Photoproduct in the Intercyclobutadiene Haptotropism of (CpCo)phenylenes |
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| Authors: | Prof. Dr. Thomas A. Albright Rima Drissi Prof. Dr. Vincent Gandon Sander Oldenhof Dr. Oluwakemi A. Oloba‐Whenu Dr. Robin Padilla Dr. Hao Shen Prof. Dr. K. Peter C. Vollhardt Vincent Vreeken |
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| Affiliation: | 1. Department of Chemistry, University of Houston, Houston, TX 77204‐5003 (USA);2. Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720‐1460 (USA), Fax: (+1)?510‐643‐5208;3. Université Paris‐Sud, ICMMO (UMR CNRS 8182), 91405 Orsay (France);4. Department of Chemistry, University of Lagos, Akoka, Yaba, Lagos (Nigeria) |
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| Abstract: | Low‐temperature irradiation of linear [3]‐ and [4]phenylene cyclopentadienylcobalt complexes generates labile, fluxional η4‐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 η2‐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. |
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| Keywords: | ab initio calculations arene ligands haptotropism isomerization photochemistry |
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