DFT‐Investigations of Pentatomic Cobalt Selenide Clusters [(CpRCo)3(μ3‐Se)2]q (CpR = Cp, Cp*; q = 2+, 1+, 0, 1‐)

Abstract

AbstractDensity functional theoretical (DFT) investigations were performed to get insight in the terminal ligands' influence on the structures of pentatomic, Cp or Cp* coated cobalt selenide clusters [(CpRCo)3(μ3‐Se)2]q (CpR = Cp, Cp*; q = 2+, 1+, 0, 1‐, referring to 48, 49, 50, 51 valence electrons; Cp* = pentamethyl‐Cp; Cp = cyclopentadienyl). The calculations reveal that for clusters with 48, 49, or 51 valence electrons, only structures with a trigonal bipyramidal Co3Se2 core (closo) represent local minima on the energy hyperface; in contrast, the 50 electron clusters can be calculated in two isomeric minimum structures each, one according to a distorted trigonal bipyramid (closo), and one with a square pyramidal core (nido). The 50 electron closo structure ‐ which disagrees with Wade‐Mingos rules ‐ was shown to be energetically preferred compared to the nido‐type Co3Se2 cage as soon as bulky ligands such as Cp* enforce a distinct enlargement of interatomic distances within the cluster core. This may explain the experimentally observed “anti‐Wade‐Mingos” structures of respective compounds like [(Cp*Co)3(μ3‐Se)2] (1).