Molecular Structure of a Doubly Ring-Slipped Ruthenocene Intermediate

We report a structural characterization of a doubly ring-slipped η¹-cyclopentadienyl ruthenocene intermediate, an analogue of putative intermediates involved in the formation and deformation of ferrocene derivatives. The thermodynamically unfavorable doubly ring-slipped intermediate was kinetically trapped using a pincer ligand, and its structure was determined using single-crystal X-ray crystallography. This intermediate quantitatively converted to a ruthenocene derivative with two η⁵-cyclopentadienyl ligands. A possible intermediate in this η¹ to η⁵ double ring-slippage was trapped by the addition of PMe₃ as an η¹, η⁵ complex. The thermodynamic preference and the kinetic barrier of the double ring-slippage were confirmed by DFT calculations, along with a possible reaction path.