Probing Fe–V Bonding in a <i>C</i>₃‑Symmetric Heterobimetallic Complex

Direct metal–metal bonding of two distinct first-row transition metals remains relatively unexplored compared to their second- and third-row heterobimetallic counterparts. Herein, a recently reported Fe–V triply bonded species, [V­(^<i>i</i>PrNPPh₂)₃FeI] (<b>1</b>; Kuppuswamy, S.; Powers, T. M.; Krogman, J. P.; Bezpalko, M. W.; Foxman, B. M.; Thomas, C. M. Vanadium–iron complexes featuring metal–metal multiple bonds. <i>Chem. Sci.</i> <b>2013</b>, <i>4</i>, 3557–3565), is investigated using high-frequency electron paramagnetic resonance, field- and temperature-dependent ⁵⁷Fe nuclear gamma resonance (Mössbauer) spectroscopy, and high-field electron-electron double resonance detected nuclear magnetic resonance. From the use of this suite of physical methods, we have assessed the electronic structure of <b>1</b>. These studies allow us to establish the effective <i><b>g̃</b></i> tensors as well as the Fe/V electro-nuclear hyperfine interaction tensors of the spin <i>S</i> = ¹/₂ ground state. We have rationalized these tensors in the context of ligand field theory supported by quantum chemical calculations. This theoretical analysis suggests that the <i>S</i> = ¹/₂ ground state originates from a single unpaired electron predominately localized on the Fe site