Complexes of iron(II) with silylated pentalene ligands; building blocks for homo- and heterobimetallics

A range of iron(II) complexes incorporating the silylated pentalene ligands (Pn † H = 1,4-{Si i Pr 3 } 2 C 8 H 5 and Pn †  = 1,4-{Si i Pr 3 } 2 C 8 H 4 ) have been investigated as model molecules/building blocks for metallocene-based polymers. Six complexes have been synthesised and extensively characterised by a range of techniques, including by cyclic voltammetry and X-ray diffraction studies. Amongst these compounds are the homobimetallic [Cp ∗ Fe] 2 (μ-Pn † ) which is a fused analogue of biferrocene, and the 3d/4s heterobimetallic [Cp ∗ Fe(η 5 -Pn † )][K] which forms an organometallic polymer in the solid state. DFT calculations on model mono-Fe(η 5 -Pn) compounds reveal the charge densities on the uncoordinated carbon atoms of the pentalene ligand, and hence the potential for incorporating these units into heteronuclear bimetallic complexes is assessed.