Investigating the structure and bonding of phosphorus, antimony, bismuth and silicon peri-substituted acenaphthenes

Abstract

The work presented in this thesis explores an array of peri-substituted acenaphthenes on the continuum of highly attractive 2c−2e donor−acceptor interactions through to repulsive, non-bonding species. Particular interest is paid to those species which contain a partial donor−acceptor 3c−4e bond, or no bond, between the peri-atoms. This is with a view to ultimately explore their propensity for undergoing intramolecular coupling reactions when subjected to thermal or radically initiated conditions, using the relief of the inherent strain as a contributor for these transformations.

A series of novel peri-substituted species containing phosphorus and either bismuth, antimony or silicon have been synthesised and, where possible, structurally characterised using single crystal X-ray diffraction. Spectroscopic analysis using a combination of multinuclear NMR, Raman and mass spectrometry has been carried out on new compounds. Those that have been isolated in a pure form have been also analysed by melting point and elemental analysis where possible.

Studies on a range of phosphorus−antimony species were carried out from non-bonding dialkylstibines, ⁱPr₂P-Acenap-SbR₂ (R = Me, ⁿBu, ⁿHex, allyl, Acenap = acenaphthene-4,5-diyl) to dative bonding species, antimony dihalides ⁱPr₂P-Acenap-SbX₂ (X = Br, I). This completed the antimony dihalide family, allowing for structural comparisons between them.

The main focus in the phosphorus−bismuth work was designing a rational synthesis to the previously serendipitously isolated ⁱPr₂P-Acenap-BiI2 compound. A small amount of crystalline material was isolated from three different methods. During this work, the unusual polycyclic species [(ⁱPr₂P-Acenap)₂][(BiPhI₃)₂], consisting of two directly bonded acenaphthene rings, was isolated as a consequence of C−H bond activation and formation of new C−P and C−C bonds.

Venturing into group 14, a range of tertiary, homo- and heteroleptic quaternary silanes were explored. The ⁱPr₂P(E)-Acenap-SiMe₃ (E = null, O, S, Se) series was synthesised and structurally characterised before being subjected to initial thermal and radically initiated elimination conditions.