Studies on the electronic structure of thiolate-bridged diiron complexes and their single-electron reduction reactions

Highlights: • A diiron complex (1²⁺) and its reduction products 2⁺ and 3 were studied. • The reduction of 2⁺ to 3 is a single-metal based process. • The bdt ligand is a dianion ligand rather than a monoanionic radical. The bdt-bridged diiron-amide complex [Cp^∗Fe(μ-η²:η²-bdt)(μ-NH₂)FeCp^∗][BF₄]₂ (1[BF₄]₂, Cp^∗ = η⁵-C₅Me₅; bdt = benzene-1,2-dithiolate) and its reduction products [Cp^∗Fe(μ-η²:η²-bdt)(μ-NH₂)FeCp^∗][BF₄] (2[BF₄]) and [Cp^∗Fe(μ-η²:η¹-bdt)(μ-NH₂)FeCp^∗] (3) have been synthesized. DFT calculations suggest that the sequential reduction of 1[BF₄]₂ to 2[BF₄] and further to 3 is a bimetal and single-metal based process, respectively. The ground state of 1[BF₄]₂ is predicted to be quartet. 2[BF₄] has an antiferromagnetic coupling BS(1,1) ground state, and the ground state of 3 is proposed to be BS(1,0). The bdt ligand in these three complexes is better viewed as a dianion ligand rather than a monoanionic radical.