5-COORDINATE HYDROGEN - NEUTRON-DIFFRACTION ANALYSIS OF THE HYDRIDO CLUSTER COMPLEX [H2RH13(CO)(24)](3-)

Pentacoordinate hydrogen atoms were identified by single-crystal neutr on diffraction analysis of [N(CH3)(4)](3)[H2Rh13(CO)(24)]. The hydroge n atoms are located in square pyramidal cavities of the Rh-13 cluster, in positions almost coplanar with the Rh-4 faces on the surface of th e cluster. They are slightly displaced inward, toward the central rhod ium atom of the cluster, with average H-Rh(central) and H-Rh(surface) distances of 1.84(2) and 1.97(2) angstroms, respectively. This result shows that hydrogen, which normally forms only one bond, can be attach ed to five other atoms simultaneously in a large metal cluster.