Solid state structure of (pentamethylcyclopentadienyl)(2,4-dimethylpentadienyl)iron, Fe(C5Me5)(2,4-C7H11), and its incorporation into silica aerogels

The structure of Fe(C5Me5)(2,4-C7H11) has been determined (C7H11 = dimethylpentadienyl), and found to be isomorphous with its ruthenium analogue. The Fe–C bond distances for the open pentadienyl ligand have been found to be about 0.02 Å shorter than those for the aromatic pentamethylcyclopentadienyl ligand, whereas for the simple cyclopentadienyl analogue, the Fe–C bond distances for the two ligand types were nearly identical. While the structural data support proposals that the pentadienyl ligand is more strongly bound, the complex reacts readily with silica aerogel, during which it is the nonaromatic pentadienyl ligand which is removed via protonation. Solid state 13C NMR spectra are consistent with incorporation of the metal into one major environment, with lesser degrees of incorporation into alternative environments.

The half-open ferrocene, Fe(C5Me5)(2,4-C7H11), has been isolated through an improved route. A structural study has found shorter Fe–C bonds for the open ligand, which nonetheless is more reactive than the aromatic C5Me5 ligand. Thus, the complex readily incorporates into aerogels through protonation of the 2,4-C7H11 ligand.Figure optionsDownload as PowerPoint slide