A remarkable mixture of germanium with phosphorus and arsenic atoms making stable pentagonal hetero-prisms [M@Ge5E5]+, E = P, As and M = Fe, Ru, Os.

A pentagonal hetero-prismatic structural motif was found for singly transition metal doped M@Ge5E5 + clusters, where the transition metal atom is located at the centre of a (5/5) Ge5E5 prism in which Ge is mixed with either P or As atoms. Structural characterization indicates that each (5/5) Ge5E5 prism is established by joining of two Ge3E2 and Ge2E3 strings in a prismatic fashion rather than two Ge5 and E5 strings. Each string results from a remarkable mixture of Ge and E atoms and contains only one E-E connection due to the fact that Ge-E bonds are much stronger than E-E connections. From the donor-acceptor perspective, the Ge5E5 tube donates electrons to the M center, which behaves as an acceptor. NBO atomic charge and ELI_D analyses demonstrate such electrostatic interactions of the M dopant with a Ge5E5 + tube which likely induce thermodynamic stability for the resulting M@Ge5E5 + cluster. CMO analysis illustrates that the conventional 18 electron count is recovered in the M@Ge5E5 + cations.