Structure and bonding of IrB12: converting a rigid boron B12 platelet to a Wankel motor

Abstract

The globalminimum of IrB12 is a C3v symmetric bowl-like structure in which the Ir atomis located on the concave side of the bowl, similar to its lighter congeners, CoB12 and RhB12 clusters. Although all these MB12 (M ¼ Co, Rh, Ir) clusters show dynamical behaviour, analogous to that of the so-called ‘Wankel motors’, the energy barrier for the rotation of the inner B3 ring within the peripheral B9 ring is the lowest in the IrB12 case (5.0 kcal mol 1 only). The geometrical feature along with the lower interaction energy between B3 and MB9 moieties are responsible for a smaller rotational energy barrier in IrB12 than those in CoB12 and RhB12 clusters

ACC thanks MICINN, project CTQ201125086/BQU and BES2012052792