Metastable Charged Dimers in Organometallic Species: A Look into Hydrogen Bonding between Metallocene Derivatives

Multiply
charged complexes bound by noncovalent interactions have
been previously described in the literature, although they were mostly
focused on organic and main group inorganic systems. In this work,
we show that similar complexes can also be found for organometallic
systems containing transition metals and deepen in the reasons behind
the existence of these species. We have studied the structures, binding
energies, and dissociation profiles in the gas phase of a series of
charged hydrogen-bonded dimers of metallocene (Ru, Co, Rh, and Mn)
derivatives isoelectronic with the ferrocene dimer. Our results indicate
that the carboxylic acid-containing dimers are more strongly bonded
and present larger barriers to dissociation than the amide ones and
that the cationic complexes tend to be more stable than the anionic
ones. Additionally, we describe for the first time the symmetric proton
transfer that can occur while in the metastable phase. Finally, we
use a density-based energy decomposition analysis to shine light on
the nature of the interaction between the dimers.