Electron-rich rods as building blocks for Sb strips and Te sheets

We analyze the bonding in a number of networks of heavy main group elements comprised of finite-length linear chains fused at right angles. Isolated linear chain building blocks may be understood easily by analogy with three-orbital four-electron "hypervalent" bonding picture in such molecules as I-3(-) and XeF2. After deriving the appropriate electron-counting rules for such linear units, we proceed in an aufbau to fuse these chains into simple land not so simple) infinite networks. It is proposed that (a) infinite Sb-3 ribbons of vertex sharing squares are stable for an electron count of 20 electrons per three atoms (i.e., Sb-3(5-)); (b) sidewise fused Sb double ribbons are stable for an electron count of 38 electrons per six atoms (i.e., Sb-6(8-)); (c) Sb-4 strips cut from a square lattice are stable at the electron count of 24 electrons per four atoms (i.e., Sb-4(4-)); (d) Te-6 defect square sheets are stable at the electron count of 40 electrons per six atoms (i.e,, Te-6(4-)). The electronic structures of the solid-state compounds containing these networks, namely La12Mn2Sb30, alpha -ZrSb2, beta -ZrSb2, Cs3Te22, and Cs4Te28, are elaborated. We propose preferred electron counts for two hypothetical Sb ribbons derived from the Sb-3 ribbon in La12Mn2Sb30. A possibility of geometry distortion modulation by excess charge in lattices comprised of even-membered linear units is suggested.