Coordination chemistry of group 14 with Pnictine Ligands and the development of precursors for the electrodeposition of antimony chalcogenides

Abstract

The work in this thesis describes the development of several new series of group 14 pnictine complexes, focusing on the generation of new neutral and cationic complexes, in conjunction with the development of new precursors for the electrodeposition of antimony chalcogenide semiconductors. Chapter 1 details the relevant background literature for the material discussed in the later chapters, with the introduction to each subsequent chapter detailing the most relevant background literature for the work described therein. Chapter 2 describes the synthesis of a series of tin(IV) halide pnictine complexes (halide = Cl, Br), as well as the halide abstraction chemistry of these complexes with TMSOTf (Me₃SiO₃SCF₃), AlX₃ and Na[BAr^F ] (BAr^F = B{3,5‐(CF₃)₂C₆H₃}₄). The effect of the halide abstractor on reaction outcome is explored. In Chapter 3 the chemistry of GeF₄ with a range of mono‐, bi‐ and multidentate phosphine ligands is explored. The reactions of the monodentate and bidentate complexes with TMSOTf are described and the effect of sequential fluoride extraction on spectroscopic and crystallographic properties investigated. The complex [GeF₃(PMe₃)₂(OTf)] was found to be unstable in solution and formed the Ge(II) complex [Ge(PMe₃)₃][OTf]₂ through reductive defluorination. This provided inspiration to investigate homoleptic pnictine‐stabilised dicationic Ge(II) complexes, as detailed in Chapter 4. The differences and similarities in the coordination chemistry of mono‐ and multi‐dentate phosphine and arsine ligands towards Ge(II) was explored mainly through single crystal XRD and NMR spectroscopic studies. Chapter 5 details the fluoride abstraction chemistry of [SnF₄(PMe₃)₂] and [SnF₄(Pⁱ Pr₃)₂] with TMSOTf, and the complexes were characterised mainly through multinuclear NMR spectroscopy (¹H, ¹⁹F{¹H}, ³¹P{¹H} and ¹¹⁹Sn). Some of the triflate complexes were shown to undergo redox chemistry in solution, including through reductive defluorination to form Sn(II) species. In Chapter 6 the chemistry of Si(IV) halides with phosphine ligands was explored and the first SiI₄ complexes with phosphine ligands are described. The halide abstraction chemistry of the lighter halide phosphine complexes is investigated providing a series of novel cationic and neutral Si(IV) complexes. The last experimental chapter describes the synthesis of new salts of [SbS₄]^3‐ with tetraalkylammonium counter cations. The electrochemistry of the anion [SbS₄]^3‐ is then investigated in aqueous and non‐aqueous solutions. In aqueous solution it has been shown that the electrodeposition of Sb₂S₃ thin films onto glassy carbon electrodes from the single source [SbS₄]^3‐ anion is possible.

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ORCID for Gillian Reid: orcid.org/0000-0001-5349-3468

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