Abstract
Centrosymmetric skutterudite RhP(3) was converted to a nonsymmorphic and chiral compound RhSi(0.3) P(2.7) (space group P2(1) 2(1) 2(1) ) by means of partial replacement of Si for P. The structure, determined by a combination of X-ray crystallography and solid state (31) P NMR, exhibits branched polyanionic P/Si chains that are unique among metal phosphides. A driving force to stabilize the locally noncentrosymmetric cis-RhSi(2) P(4) and fac-RhSi(3) P(3) fragments is π-electron back-donation between the Rh t(2g) -type orbitals and the unoccupied antibonding Si/P orbitals, which is more effective for Si than for P. In situ studies and total energy calculations revealed the metastable nature of RhSi(0.3) P(2.7) . Electronic structure calculations predicted centrosymmetric cubic RhP(3) to be metallic which was confirmed by transport properties measurements. In contrast, the electronic structure for chiral orthorhombic RhSi(0.3) P(2.7) contained a bandgap, and this compound was shown to be a narrow gap semiconductor.