Metal cluster chemistry: Structure and stereochemistry in the polynuclear rhodium hydrides H\u3csub\u3en\u3c/sub\u3eRh\u3csub\u3en\u3c/sub\u3e[P(OR)\u3csub\u3e3\u3c/sub\u3e]\u3csub\u3e2n\u3c/sub\u3e

Abstract

Crystallographic analyses of x-ray and neutron diffraction data have provided a definitive structural representation of {HRh[P(O-i-C3H7)3]2}2 and [HRh[P(OCH3)3]2}3. These polynuclear hydrides are generated from square planar H2Rh[P(OR)3]2 units by edge (hydrogen atom) sharing and by vertex (hydrogen atom) sharing to form the dimeric and trimeric structures, respectively. The square-planar units are held together through four-center and three-center two-electron Rh-H-Rh bonds in the dimer and trimer, respectively. The dimer and trimer molecules each add one molecule of hydrogen to form H[(i-C3H7O)3P]2RhH3Rh[P(O-i-C3H7)3]2 and H5Rh3[P(OCH3)3]6, respectively. NMR spectral information has served to define the stereochemical features of these polyhydrides. The significance of this chemistry in the metal clustermetal surface analogy is described