MH50/+/-: σ Aromatic Cluster

Aromaticity is one of the central concepts in chemistry. Herein, quantum chemical calculations have been carried out to search for σ aromatic metal pentahydrides of the general formula MH5- (M = Ni, Pd, Pt). All these group 10 metals form true local minimum in their planar D5h symmetry. The presence of σ aromaticity in these clusters were ascertained from molecular orbital, electron density of delocalized bonds (EDDB) and iso-chemical shielding surface (ICSSZZ) analyses. Detailed potential energy surface analyses reveal that D5h geometry of PtH5- is the lowest energy one while NiH5- and PdH5- clusters form stable C2V dihydrogen M(η2-H2)H3 complexes. Similarly, M(η2-H2)H3 geometry is the lowest energy one for AuH5 cluster. However, D5h geometry of CsH5 and BaH5+ is the lowest one with aromatic character.