Add a Pinch of Tetrel: The Transformation of a Centrosymmetric Metal into a Nonsymmorphic and Chiral Semiconductor

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.