  A central theme in chemistry is the understanding of the mechanisms that
drive chemical transformations. A well-known, highly cited mechanism in
organometallic chemistry is the superexchange mechanism in which unpaired
electrons on two or more metal centers interact through an electron pair of the
bridging ligand. We use a combination of novel synthesis and computation to
show that such interactions may in fact occur by a more direct mechanism than
superexchange that is based on direct quantum entanglement of the two metal
centers. Specifically, we synthesize and experimentally characterize a novel
cobalt dimer complex with benzoquinoid bridging ligands and investigate its
electronic structure with the variational two-electron reduced density matrix
method using large active spaces. The result draws novel connections between
inorganic mechanisms and quantum entanglement, thereby opening new
possibilities for the design of strongly correlated organometallic compounds
whose magnetic and spin properties have applications in superconductors, energy
storage, thermoelectrics, and spintronics.
