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.