Abstract

Iron(II) Coordination Complexes with PPh2Py and DPEphos Ligands

Author(s): Malabika Borah, Nabanita Saikia, Pankaj Das*

Metal Iron(II) complexes [FeCl₂(η²-P,N-PPh₂Py)₂] (1) and [FeCl₂(η²-P,P-DPEphos)₂] (2), with PPh₂Py and DPEphos ligands were synthesized and characterized by elemental analysis, ESI-Mass, FTIR, UV-Vis, ¹H and ³¹P{¹H} NMR spectroscopy. The FTIR studies predicted cis-isomer to be the most stable form of complex 1 and trans-isomer as the most stable form of complex 2. Quantum chemical calculations using first-principles Density Functional Theory (DFT) in gas phase were performed on the two complexes at the B3LYP/LANL2DZ/6-31+G (d,p) level of theory. Theoretical calculations predicted the ground state of the complexes to be quintet spin state. However, in complex 1, quintet spin state led to a significant elongation in Fe–P bond length to ~3.55 Å. Thus, singlet (S=1/2) spin state was considered for complex 1 which showed reasonable agreement with calculated geometric parameters. Trans-configuration of complex 2 was shown to have a higher HOMO-LUMO energy gap (higher stability) than complex 1 which can be attributed to nature of ligand coordinated to Fe(II) ion.