A planar pentacoordinate oxygen in the experimentally observed [Be 5 O 6 ] 2− dianion

Sharing the molecular formula of [Be 5 O 6 ] 2– generated by electrospray ionization in 2006, D 5h [O©Be 5 O 5 ] 2– was identified here as a global energy minimum, representing the first experimental observation of a non-classical planar pentacoordinate oxygen.