Uranium clusters aromaticity

Very recently we have communicated on the role of the 5f orbitals in bonding, aromaticity, and reactivity of planar isocyclic and heterocyclic uranium clusters [185]. Using electronic structure calculation methods (DFT) we demonstrated that the model planar isocyclic cjc/o-U X (n = 3, 4 X = 0,NH) and heterocyclic cjc/o-U (/u.2-X) (n = 3, 4 X = C, CH, NH) clusters are thermodynamically stable molecules with respect to their dissociation either to free U and X moieties or to their monomeric UX species. The equilibrium geometries of the cyclo- J X and cyclo-U iJ,2-X) clusters are shown in Fig.42. 

Tsipis AC, Kefalidis CE, Tsipis CA (2008) The role of the 5f orbitals in bonding, aromaticity, and reactivity of planar isocycUc and heterocyclic uranium clusters. J Am Chem Soc 130 9144-9155... 

It is evident that the 5f orbitals of the uranium metal centers play a key role in the bonding of the aforementioned f-block metal systems significantly contributing to the cyclic electron delocalization and the associated magnetic diatropic response. The aromaticity of the cyclo-U X (n = 3,4 X = OH, NH) and cycZo-U (/tt2-X) (n = 3, 4 X = C, CH, NH) clusters was verified by the magnetic criterion of... 

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