Silane, Germane, and Stannane Activation by an Iron Dinitrogen Compound to Access Dimetallotetrylides

Upon adding Group 14 hydride gases to the recently prepared iron dinitrogen dimer, [(Triphos)Fe]2(μ-N2) (Triphos = H3CC(CH2PPh2)3), a generalized methodology for the preparation of diirontetrylides has been realized. The all-bond activation of SiH4 afforded the corresponding silicide, (Triphos)(H)2Fe═Si═Fe(H)2(Triphos), which was found to feature a linear Fe2Si core by single-crystal X-ray diffraction. Activation of GeH4 and SnH4 by [(Triphos)Fe]2(μ-N2) yielded (Triphos)(H)2Fe═Ge═Fe(H)2(Triphos) and (Triphos)(H)2Fe═Sn═Fe(H)2(Triphos), respectively, which exhibit bent cores and short iron-tetrel distances indicative of double-bond character. Each dimetallotetrylide possesses cis-hydride ligands that are coupled to magnetically equivalent Triphos phosphine positions, but not the bridging tetrel atom, in solution at ambient temperature. Computational studies revealed optimized geometries that are consistent with the solution-phase structures, as well as iron-tetrel bond orders that decrease from 1.55 (Si) to 1.43 (Ge) to 1.27 (Sn) upon descending Group 14, an observation attributed to decreasing π-overlap.