Inorganic Ring Systems

Abstract

Inorganic rings of various types can be formed as a result of the broad range of bond types available. Cyclic structures formed by self‐assembly of molecular building units (tectons) are discussed in terms of supramolecular chemistry concepts. The formation of covalent rings can be understood in terms of combining various fragments (synthons) in which the central atoms can display various oxidation states, coordination numbers, and geometries, leading to a broad structural diversity of cyclic structures for a given composition of the ring skeleton (as illustrated for P 2 N 2 and Si 2 N 2 rings).

Aluminium and gallium trihalide adducts of 2,4,6-triorganylborazines and the synthesis of triorganylborazinium tetrabromoaluminates1

“…But even more interesting is the fact that the AlBr 3 adducts react with HBr to form the hitherto unknown borazinium salts [R 3 B 3 MN 3 H 4 ]AlBr 4 . There is a close structural relationships between the adducts and the borazinium cations.…”

“…[2][3][4][5] This is due to the inherent B-N bond polarity which places a partial negative charge on the nitrogen atoms and a partial positive charge on the boron atoms. For example: borazine (HB=NH) 3 adds 3 equivalents of HBr or HCl to form the cycloborazane [H(X)B-NH 2 ] 3 6 and HCl adds to (ClB=NMe) 3 with formation of (Cl 2 B-NHMe) 3 .…”

“…However, its formation can be expected when the halide anion is replaced by a less nucleophilic and larger anion. From this point of view one may expect that trifluromethylsulfonic acid would be a candidate for borazinium salt formation, as well as HSbF 6 or H[Al(Hal) 4 ]. In this study we reacted HBr with the borazine aluminium tribromide adducts 3 and 5 in toluene in order to generate the comparatively large tetrabromoaluminate.…”

The Molecular Structure of 1,3,5,7- Tetra(tert-butyl)-2,4,6,8-tetraazidoborazocine [1]

“…Amongst the BN heterocycles (XB=NR) n those of the eight-membered borazocines (XB=NR) 4 , which are isoelectronic with cyclooctatetraene, have not been extensively studied in comparison to the sixmembered borazines (XB=NR) 3 [2 -4]. Actually, the latest report dates back to the year 1979 [5].…”

Structural and Molecular Orbital Properties of Some Boroxine Derivatives-A Theoretical Study

“…19 The chemistry of triorganoboroxines is dominated by ringcleavage reactions. 20 Apart from the synthetic approaches to the boroxine derivatives, there have been many theoretical studies on boroxine and its derivatives. Among them; Beckmann et al, investigated ring strain in boroxine rings, 21 Doerksen and Thakkar computed the bond orders, quadrupole and octopole moments of some heterocyclic molecules, including boroxine, 22,23 ring currents and aromaticity of monocyclic systems have been studied by Fowler and Steiner, 24 and Tossell investigated the structure, polarizability and vibrational spectra of boroxine.…”