Ruthenocene Precursors for Ruthenium-Containing Thin-Film Deposition: An Example of Solvent Nucleophilic Attack on Fulvene

A new series of ruthenocene complexes were prepared from RuCl₃·<i>x</i>H₂O and 6,6-dimethylfulvene as potential precursors for thin-film deposition. The formation of these complexes was the result of an unforeseen nucleophilic attack of the solvent molecules (alcohols/amines) on the 6,6-dimethylfulvene ligand during the reaction. Complexes [Ru^II(C₅H₄C­(CH₃)₂OCH₃)₂] (<b>1</b>), [Ru^II(C₅H₄C­(CH₃)₂OC₂H₅)₂] (<b>2</b>), [Ru^II(C₅H₄C­(CH₃)₂N­(CH₃)₂)₂] (<b>3</b>), and [Ru^II(C₅H₄C­(CH₃)₂N­(CH₂CH₃)₂)₂] (<b>4</b>) were isolated in pure form and characterized by Fourier transform (FT) infrared and FT nuclear magnetic resonance spectroscopy as well as elemental and thermogravimetric (TG) analyses. Crystallographic studies of complexes <b>1</b>–<b>3</b> revealed a monomeric ruthenocene structure for all complexes and showed that the deprotonated alkylalkoxide or dialkylamide of the solvent molecule was attached to the exocyclic carbon of the fulvene ligand. Although the complexes were formed as ruthenocenes instead of the expected ruthenium fulvene complexes, they all displayed excellent stabilities and thermal properties. In particular, complexes <b>3</b> and <b>4</b> emerged as the best compounds owing to their clean TGA plot and excellent volatility, holding the potential as precursors for thin-film deposition