Table 3.
A comparison of calculated and experimental covalency values for covalency for the compounds: [Fe(tpp)(ImH)2]+, [Fe(tacn)2]3+, [Fe(tpp)(ImH)2] and [Fe(tacn2)]2+
| Total Intensity | % Total Metal Character in unoccupied orbitals† (based on Intensity) | % Total Metal character in unoccupied orbitals† (based on DFT) | A Comparison of VBCI and DFT values for Differential Orbital Covalency. VBCI(DFT) % | |||||
|---|---|---|---|---|---|---|---|---|
| B1 (x2-y2) | A1 (z2) | B2 (xy) | E1 ** (xz, yz) | π* (xz, yz) | ||||
| [Fe(tacn)2]Cl3 | 43.8 | 351 | 333 | 63(64) | 63(64) | 99 (93) | 99(93) | |
| [Fe(tacn)2]Cl2 | 37.4 | 295 | 284 | 74(72) | 74(72) | (93) | (93) | |
| A. [Fe(tpp)(ImH)2] Fe(II) π back-bonding only | 39.0 | 309 | 314 | 73(66) | 73(66) | (83) | (78) | 7(9) |
| B. [Fe(tpp)(ImH)2] Fe(II) σ,π donation, + π back-bonding | 39.0 | 309 | 314 | 65(66) | 67(66) | (83) | (78) | 11(9) |
| A. [Fe(tpp)(ImH)2]Cl Fe(III) σ,π donation only | 38.3 | 303 | 333 | 54(66) | 68(62) | 93 | 58(71) | (2) |
| B. [Fe(tpp)(ImH)2]Cl Fe(III) σ,π donation, + π back-bonding | 38.3 | 303 | 333 | 52(66) | 68(62) | 93 | 57(71) | 2(2) |
**
DFT values for the dxz and dyz orbitals were averaged for comparison to the VBCI model in D4h symmetry. The values for each orbital are given in Table 1.
†
The % metal character summed over unoccupied orbitals reflects the combined effects of covalency and back-bonding. In a system with no back-bonding this number divided by the number of holes gives the average % metal character in each orbital. For example, [Fe(tacn)2]Cl3, 351/5 =70%, (63*4+99)/5=70