A study of the molecular and electronic structure of iron(ii) and ruthenium(ii) 1,3-di- and 1,2,4-tri-phospholyl sandwich compounds by photoelectron spectroscopy and density functional theory

Abstract

The synthesis and variable temperature ¹H NMR spectrum of the new tetraphosphaferrocene [Fe(η⁵-P₂C₃Bu₃^t)₂] are presented and the photoelectron spectra are reported for [Fe(η⁵-P₃C₂Bu₂^t)₂] 1a, [Fe(η⁵-P₂C₃Bu₃^t)₂] 2a, [Fe(η⁵-P₂C₃Bu₃^t)(η⁵-P₃C₂Bu₂^t)] 3a and [Ru(η⁵-P₃C₂Bu₃^t)₂] 4a. Density functional calculations were used to optimise the geometry and calculate the ionization energies of the parent analogues. Good agreement was obtained with the experimental results, giving support to the theoretical modelling of these sandwich compounds. Analysis of their electronic structure showed that replacement of RC fragments by P atoms in the η⁵-ligated cyclopentadienyl rings increases their acceptor properties. Extensive σπ mixing makes the description of the orbitals complex. Some higher lying Pσ levels are found to have similar ionization energies to the d electrons.