Heterobimetallic complexes of IrM (M = FeII, CoII, and NiII) core and bridging 2-(diphenylphosphino)pyridine: electronic structure and electrochemical behavior

Abstract

Three complexes based on an Ir-M (M = Fe^II, Co^II, and Ni^II) heterobimetallic core and 2-(diphenylphosphino)pyridine (Ph₂PPy) ligand were synthesized via the reaction of trans-[IrCl(CO)(Ph₂PPy)₂] and the corresponding metal chloride. Their structures were established by single-crystal X-ray diffraction as [Ir(CO)(μ-Cl)(μ-Ph₂PPy)₂FeCl₂]·2CH₂Cl₂ (2), [IrCl(CO)(μ-Ph₂PPy)₂CoCl₂]·2CH₂Cl₂ (3), and [Ir(CO)(μ-Cl)(μ-Ph₂PPy)₂NiCl₂]·2CH₂Cl₂ (4). Time-dependent DFT computations suggest a donor-acceptor interaction between a filled 5d_z² orbital on iridium and an empty orbital on the first-row metal atom, which is supported by UV-vis studies. Magnetic moment measurements show that the first-row metals are in their high-spin electronic configurations. Cyclic voltammetry data show that all the complexes undergo irreversible decomposition upon either reduction or oxidation. Reduction of 4 proceeds through an ECE mechanism. While these complexes are not stable to electrocatalysis conditions, the data presented here refine our understanding of the bonding synergies of the first-row and third-row metals.