Table 2.
Assignment of the Infrared (IR) and resonance Raman (rR) spectra of (μ-edt)[Fe(CO)3]2 and (μ-edt)[Fe(13CO)3]2 focusing on the ν(C=O) and ν(Fe-CO)/δ(Fe-C=O) regions.
| Mode | Symmetrya (ax ± eq) | Experimental/cm−1 | Calculated/cm−1 | ||
|---|---|---|---|---|---|
| IRb (12CO/13CO) | rRc (12CO/13CO) | DFTd | NCAe (12CO/13CO) | ||
| ν(C=O) | A1 + A1 | 2078(2077)/2030 | 2070/2023 | 2153 m, IR; m, Raman |
2069/2020 |
| ν(C=O) | B2 + B2 | 2038(2037)/1991 | 2005/1959 | 2105 vs, IR; vw, Raman |
2006/1959 |
| ν(C=O) | A1 − A1 | 2008(1998)/1962 | 1979/1934 | 2095 s, IR; m, Raman |
1980/1934 |
| ν(C=O) | B1 | 1995/1950 | 1968/1924 | 2083 s, IR; m, Raman |
1968/1922 |
| ν(C=O) | A2 | not observed | 1964/1919 | 2076 na, IR; m, Raman |
1963/1918 |
| ν(C=O) | B2 − B2 | 1985/1940 | 1961/1917 | 2072 w, IR; m, Raman |
1960/1915 |
| ν(Fe-CO) + δ(Fe-C=O) | A1 + A1 | 630/615 | 636 w, IR; vw, Raman |
628/617 | |
| ν(Fe-CO) + δ(Fe-C=O) | A1 − A1 | 592/579 | 601 w, IR; vw, Raman |
594/578 | |
| ν(Fe-CO) + δ(Fe-C=O) | B1 − B1 | 572/562 | 578 w, IR; vw, Raman |
573/562 | |
| ν(Fe-CO) + δ(Fe-C=O) | A2 − A2 | 565/556 | 571 na, IR; vw, Raman |
567/556 | |
| δ(Fe-C=O) | B1 + B1 | 528/519 | 526 vw, IR; vw, Raman |
528/518 | |
| ν(Fe-CO) + δ(Fe-C=O) | A1 − A1 | 503/495 | 507 w, IR; vw, Raman |
506/496 | |
| ν(Fe-CO) + δ(Fe-C=O) | A2 + A2 | 494/485 | 496 na, IR; vw, Raman |
496/482 | |
| ν(Fe-CO) + δ(Fe-C=O) | B1 − B1 | 483/474 | 481 vw, IR; w, Raman |
482/475 | |
| ν(Fe-CO) + δ(Fe-C=O) | B2 − B2 | 470/462 | 471 vw, IR; vw, Raman |
473/465 | |
| ν(Fe-CO) + δ(Fe-C=O) | A2 | 463/452 | 454 na, IR; vw, Raman |
461/449 | |
| ν(Fe-CO) + δ(Fe-C=O) | A1 − A1 | 456/444 | 448 vw, IR; w, Raman |
453/442 | |
| ν(Fe-CO) + δ(Fe-C=O) | B1 | 454/442 | 446 vw, IR; w, Raman |
452/441 | |
| ν(Fe-CO) + δ(Fe-C=O) | B2 − B2 | 447/435 | 440 w, IR; vw, Raman |
444/432 | |
| δ(Fe-C=O) | A2 + A2 | 419/406 | 416 na, IR; vw, Raman |
422/408 | |
| δ(Fe-C=O) | B1 + B1 | 416/403 | 410 vw, IR; vw, Raman |
416/403 | |
Symmetry labels are given based on the C2v symmetry of the molecule; ax = axial, eq = equatorial. In A1+A1, for example, the first symmetry label corresponds to the symmetry of the axial internal coordinate; the second corresponds to the equatorial internal coordinate that the normal mode is comprised of (+ = in-phase combination).
Vibrational IR energies were obtained in hexane and acetonitrile (in parenthesis).
From resonance Raman measurements on a saturated solution in acetonitrile.
Using B3LYP/TZVP. Intensities are classified as: vs = very strong; s = strong; m = medium; w = weak; vw = very weak.
Vibrational energies obtained from Normal coordinate analysis (NCA) using vibrational frequencies from the rR spectra.