Analysis of the characteristic vibrations and their force constants (in parenthesis) as well as XRD data of M(CO)6 and [M(CO)6]+ (M: Cr, Mo, W) as [F-{Al(ORF)3}2]− salts. DFT: BP86-D3BJ/def2-TZVPP Oh (neutral carbonyls) and D3d (cations) symmetry; force constants were calculated with Gaussian @BP86/def2-TZVPP, calc. CO(g) as reference: 2123 cm−1 (35.70 × 102 N m−1).
| [Cr(CO)6]+˙ | [Mo(CO)6]+˙ | [W(CO)6]+˙ | Cr(CO)6 | Mo(CO)6 | W(CO)6 | |
|---|---|---|---|---|---|---|
| IR ν(CO)a/cm−1 A2u/Eu | 2096 | 2089 | 2075 | |||
| DFT ν(CO)a/cm−1 (102 N m−1) A2u/Eu | 2081(33.78) | 2072(33.78) | 2062(33.46) | |||
| Raman ν(CO)/cm−1 A1g | 2173 | 2173 | 2173 | 2110 | 2115 | 2115 |
| DFT ν(CO)/cm−1 (102 N m−1) A1g | 2158(36.39) | 2158(36.33) | 2155(36.18) | 2104(34.50) | 2105(34.51) | 2104(34.41) |
| DFT ν(M–C)/cm−1 (102 N m−1) A1g | 364(1.07) | 385(1.20) | 403(1.31) | 406(1.34) | 418(1.43) | 435(1.56) |
| XRD d(M–C)/pm | 198.2(2) | 210.5(7) | 210.5(9) | 191.5(1)36 | 205.9(4)37 | 204.9(5)38 |
| XRD d(C–O)/pm | 112.2(2) | 112.0(8) | 110.8(11) | 114.2(1)36 | 113.4(6)37 | 113.6(9)38 |
| DFT d(M–C)/pm | 197.5 | 209.9 | 210.4 | 190.2 | 205.5 | 206.7 |
| DFT d(C–O)/pm | 113.9 | 113.9 | 114.1 | 115.2 | 115.2 | 115.3 |
| FIAb/kJ mol−1 | 711 | 715 | 741 |
a
IR: overlap of A2u and Eu CO vibration.
b
Fluoride ion affinities FIAs referenced to [Si(CH3)3]+ = 958 kJ mol−1.39