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.

Date of Award	30 Nov 2021
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Petr Kilian (Supervisor)