Niobium triangular clusters

Cluster complexes that obey Cotton s strict definition such as [ Nb6 Cli8]K4 and [ Mo6 C1h]Cs2 have 16 and 24 electrons, respectively, for bonding interactions within the octahedral niobium and molybdenum clusters. In a VB picture, these electrons are consumed for eight two-electron-three-center (2e-3c) or 12 2e-2c bonds, situated in the eight triangular faces and the 12 edges of the respective octahedra. 

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