Figure 2.

⁵⁷Fe-PVDOS vibrational energies in 1 and 1-D₂ characterized by NRVS experiments (a) and DFT calculations (b). DFT-computed modes of predominantly hydride motion character are further revealed via 2×H⁻/D⁻-specific PVDOS and vibrational mode assignments with respect to the Fe(μ-H)₂Fe core of 1 (c). For the DFT ⁵⁷Fe-PVDOS, stick-style spectra are additionally shown (b). The ×5 intensity insets display ⁵⁷Fe-PVDOS spectra >430 cm⁻¹, where equivalences between the observed and computed bands are indicated by broken vertical lines. Data for 1 are in blue, and for 1-D₂ are in red, including the band positions; the bands labeled in gray are common in both isotopologues. Tentatively assigned weak NRVS features are in semi-transparent colors. The combined low- and high-energy region-of-interest (ROI) NRVS scans for 1 are additionally provided in Figure S6.