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Reactions of nine-atom deltahedral clusters of germanium with Ni(COD)2 and/or Ni(PPh3)2(CO)2 in ethylenediamine yielded the Ni-centered heteroatomic 10-atom clusters Ni@(Ge9Ni-CO)2- and Ni@(Ge9Ni-en)3-, as well as the empty 10-atom heteroatomic cluster Ge9Ni-CO3-. A ligand exchange reaction between Ni@(Ge9Ni-CO)2- and potassium phenylacetylide produced the organically functionalized species Ni@(Ge9Ni-CCPh)3-. The empty cluster Ge9Ni-CO3- is a bicapped square antiprism where one of the capping vertexes is the nickel atom. The other three clusters are tricapped trigonal prisms where an additional 10th vertex of monoligated nickel caps a triangular base of the trigonal prism. As a result of this, that base opens up, and the distances within it become nonbonding. This ensures that all atoms of the cluster are equidistant from the central nickel atom, i.e., the cluster is very close to spherical. All species were structurally characterized in crystalline compounds with K-(2,2,2-crypt)+ countercations. They were also characterized in solution by mass spectrometry, IR, and 13C NMR.
Goicoechea et al. (Wed,) studied this question.