Metal cluster topology: Part 8. Six-vertex polyhedral metal carbonyl clusters and their skeletal rearrangements

Abstract

Among the seven topologically distinct six-vertex polyhedra only the regular octahedron has no degree three vertices and thus is the only six-vertex polyhedron forming globally delocalized metal carbonyl clusters. Five of the remaining six topologically distinct six-vertex polyhedra have been found in metal carbonyl clusters having numbers of skeletal electrons indicative of edge-localized bonding. Gale diagrams are used to depict the following experimentally observed skeletal rearrangements in six-vertex metal carbonyl clusters: (a) trigonal prism to octahedron; (b) pentagonal pyramid to C s, 6,11,7-polyhedron; (c) C 2 6,10,6 polyhedron to C s, 6,11,7 polyhedron; and (d) bicapped tetrahedron to octahedron through a C 2v 6,11,7 polyhedron (“diagonally deficient cube”). The inability to obtain a stable metal carbonyl cluster based on the C 2v diagonally deficient cube may relate to the fact that this polyhedron can be converted to the regular octahedron by adding an edge without changing the skeletal electron count.