Topology-Dependent Synthesis, Structures, and Bonding Interactions of Uranium Polyarene Complexes

Metal polyarene complexes have attracted great attention
in recent
years because of their appealing electronic structures and readily
tunable properties and reactivity. While main group and transition
metal polyarene complexes have been well studied with various degrees
of reduction and different coordination modes, f-block metal polyarene
complexes are rare. Here we report the synthesis of a series of uranium
polyarene complexes supported by ferrocene diamide ligands. X-ray
crystallography shows that the structures of uranium polyarene complexes
are dependent on the topology of polyarenes. While linear polyarenes
form mononuclear compounds, nonlinear polyarenes prefer an inverse-sandwich
structure with a μ-η6,η6-coordination
mode. Combined experimental and computational studies unveil that
mononuclear uranium polyarene complexes are best described as bidentate
with a three-center two-electron (3c-2e) σ bond, whereas inverse-sandwich
uranium polyarene complexes are bound through two δ bonds. The
correlation between the topology of polyarenes and the coordination
mode of uranium polyarene complexes can be rationalized by the electronic
structures and bonding interactions as well as the relative energies
of coordination isomers.