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

In this work we seek to understand the pre-catalytic initiation steps in a classic metallaphotoredox catalysis paring Ir(III) ((Ir[dF(CF$_{3}$)ppy]$_{2}$(dtbbpy))PF$_{6}$) and Ni(II) ((4,4'-dtbbpy)NiCl$_{2}$) in dimethoxyethane. We use a combination of transient X-ray and optical absorption spectroscopies to track both nuclear and electronic excited-state dynamics, revealing two steps. First, photoexcitation produces the expected intramolecular oxidation of the iridium center, Ir(III), to Ir(IV)(dtbbpy)$^{\bullet -}$ correlated to the Ir metal-to-ligand charge transfer state. Second, interaction with Ir(IV)(dtbbpy)$^{\bullet -}$ drives the tetrahedral Ni(II) starting material to an unexpected octahedral Ni(II) species. We conclude by proposing the identity of the octahedral Ni(II) and suggest both an electron and an energy transfer mechanism for producing it that are equally consistent with our observations.