Precursors for doped boron carbide thin films

This Thesis is concerned with the development of high yield synthetic strategies to phosphaboranes and phosphacarboranes. These compounds have attracted attention due to their potential as single-source precursors for the deposition of thin films of doped boron carbide via plasma enhanced chemical vapour deposition. It has shown that suitable doping of the boron carbide can lead to wide band gap semiconductors and incorporation of phosphorus into the cage structure of the solid-state material is one way of achieving this aim.Chapter one discusses the chemical vapour deposition of boron carbide and goes on to describe its uses as neutron detectors and semiconductors. Chapter two presents the existing methods used for the synthesis of aminophosphines and highlights the importance of two such species, PH(NBus2 )2 and PCl2N(CJln)2 .The remaining chapters cover the experimental work used for the preparation of phosphaboranes and phosphacarboranes that contain the phosphorus atom as a vertex. Chapter three focuses on the reaction of bis(dialkylamino)phosphines with decaborane and describes the synthesis of the nido-[l-nido-?^\o\\\2\ anion in high yield. In Chapter four, the use of the nido-[l-PB}oH\2\ anion to prepare a range of cluster complexes via reaction with a variety of electrophiles is discussed. Chapter five focuses on the reaction of bis(dialkylamino)phosphines with nido-5,6- dicarbadecaborane(12) and describes the synthesis of novel compounds of the formulae 6,9-R2NHP-5,6-C2 Bs Hn, (R = Pr', Bu1 ). This is considered as an intermediate product which subsequently gives a mixture of the nit/-7,8,\ 1- PC2B8Hn, mWo-[7,8,9-PC;>BxHio]~ and /m/o-[7,8,l 1-PC:B8 H IO ] species whose ratio is dependant on the R group. Each chapter contains a brief introduction, discusses the results obtained including multinuclear NMR spectroscopy and crystal structure data and concludes with an experimental section