Tetrahedral to Octahedral Nickel(II) as an Initiation Step in Metallaphotoredox Catalysis

Anna Zieleniewska, Justin Earley, Jin Yu, Agustin Millet, Daniela Arias-Rotondo, Amy Cordones-Hahn, Max Kudisch, David MacMillan, Xiaoyi Zhang, Garry Rumbles, Obadiah Reid

Research output: Contribution to journalArticle


In this work we seek to understand the pre-catalystic initiation steps between two metallaphotoredox catalysts Ir(III) ((Ir[dF(CF3)ppy]2}(dtbbpy))PF6) and Ni(II) ((4,4'-dtbbpy)NiCl2) using a combination of X-ray and optical spectroscopies. We observe two steps: first, photoexcitation produces the expected intramolecular oxidation of Ir(III) to Ir(IV)(dtbbpy)- correlated to the Ir metal-to-ligand charge transfer state, rather than Ir(II) which is often reported in literature. Second, the 4-coordinate Ni(II) starting species evolves to a 6-coordinate Ni(II) species after oxidation by Ir(IV)(dtbbpy)-. We conclude by proposing the identity of the 6-coordinate Ni(II) species and its potential importance in the pre-mechanistic step prior to Ni entering the catalytic cycle. This neglected 6-coordinate Ni(II) intermediate could help to unravel the poorly understood initiation step in these metallaphotoredox C_sp3-C_sp2 cross-coupling reactions.
Original languageAmerican English
Number of pages12
StatePublished - 2023

NREL Publication Number

  • NREL/JA-5900-85993


  • catalysis
  • iridium
  • metallaphotoredox
  • nickel
  • oxidation
  • pre-catalytic
  • x-ray


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