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

Quantum 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. [ABSTRACT FROM AUTHOR]