Manganese-centered ten-vertex germanium clusters: the strong field Ge<sub>10</sub> ligand encapsulating a transition metal

2015-10-08T16:44:15Z (GMT) by M. M. Uţă R. B. King
<div><p>The experimental realization of pentagonal prismatic structures for M@ (M = Co, Fe) containing interstitial transition metal atoms makes of interest the chemistry of corresponding manganese derivatives Mn@. The neutral Mn@Ge<sub>10</sub> may be regarded as a complex of a polyhedral ligand with an interstitial Mn in the +2 oxidation state. However, the lowest energy Mn@Ge<sub>10</sub> structure with the expected sextet spin state for high-spin d<sup>5</sup> Mn(II) lies ~23 kcal mol<sup>−1</sup> in energy above the lowest energy isomer thereby suggesting that such germanium polyhedra function as strong field ligands for encapsulated transition metals. The lowest energy structures for the Mn@ anions (<i>z</i> = −1 to −5) are all centered pentagonal prisms. Higher energy Mn@ structures have outer Ge<sub>10</sub> polyhedra based on the tetracapped trigonal prism similar to the lowest energy Co@ structure and on the bicapped square antiprism similar to the B<sub>10</sub> deltahedron. Other Mn@ structures have outer Ge<sub>10</sub> polyhedra with four or five quadrilateral faces as well as six or eight triangular faces, respectively. Bioctahedral (Ge<sub>5</sub>)<sub>2</sub>Mn<sup>5−</sup> structures were also found for the pentaanion with a manganese vertex common to two MnGe<sub>5</sub> octahedra. The cationic species Mn@ was found to have a more complicated potential surface than the anions. Tetracapped trigonal prismatic and bicapped square antiprismatic structures as well as a variety of more open structures were found for Mn@.</p></div>