Structures and Bonding Situation of Iron Complexes of Group‐13 Half‐Sandwich ECp* (E = B to Tl) Based on DFT Calculations

Abstract

AbstractQuantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, and TZ2P+) were carried out for the Fe(CO)4 of group‐13 half‐sandwich ECp* [Fe(CO)4‐ECp*] (Fe4‐E) (E = B to Tl). The chemical bonding of the Fe(CO)4‐ECp* bond was analyzed with charge‐ and energy decomposition methods. The calculated equilibrium structures of complexes Fe4‐E show that the ligands ECp* are bonded in an end‐on way to the fragment Fe(CO)4 in Fe4‐E with E = B to Ga. The compound Fe4‐In has a distorted end‐on ligand InCp*. In contrast, Fe4‐Tl has a side‐on bonded ligand TlCp*. The calculated bond dissociation energies (BDEs) suggest that the bond in the iron group‐13 half‐sandwich complexes Fe4‐E decreases from Fe4‐B to Fe4‐Tl. Natural bond orbital (NBO) analysis of the bonding situation reveals that the Fe(CO)4←ECp* donation in Fe4‐E comes from the σ lone‐pair orbital of ECp*. Bonding analysis indicates that the ligand ECp* in complexes are strong σ donors and the NOCV pairs of the bonding show small π‐back donation from the Fe(CO)4 to the ECp* ligands.