Diiron µ₂-N₂ complexes in bimetallic, four-fold bond activations of SiH₄ to produce µ₂-silicide complexes

Fe(0) dinitrogen complexes [SiP₃ ^R]Fe-N[triple bond, length as m-dash]N-Fe[SiP₃ ^R] (1-R; [SiP₃ ^R] = PhSi(CH₂PR₂)₃; R = ⁱ Pr, Ph) are accessed by one- or two-electron reduction of Fe(i) and Fe(ii) chloride complexes [SiP₃ ^{i Pr}]FeCl or κ²-[SiP₃ ^R]FeCl₂ (R = ⁱ Pr, Ph), respectively, and fully characterized by means of multinuclear NMR spectroscopy, single-crystal X-ray diffraction (SC-XRD), and Mössbauer spectroscopy. Complexes 1-R represent rare examples of bimetallic Fe(0) compounds with dinitrogen as a bridging ligand and have an overall spin of S = 0. Heating 1-R in the presence of SiH₄ gas resulted in four-fold Si-H activation to furnish diiron complexes [SiP₃ ^R](H)₂Fe[double bond, length as m-dash]Si[double bond, length as m-dash]Fe(H)₂[SiP₃ ^R] (2-R; R = ⁱ Pr, Ph), which were characterized by multinuclear NMR spectroscopy, SC-XRD, Mössbauer spectroscopy, and density functional theory calculations. Complexes 2-R exhibit the shortest iron-silicon bonds to date and nearly linear Fe[double bond, length as m-dash]Si[double bond, length as m-dash]Fe cores. This work extends a previously developed strategy for SiH₄ activation from cobalt to iron, while offering insight into the silicon-atom extrusion from SiH₄ in molecular systems.