Phosphine-porphyrin conjugates : a thesis presented in partial fulfilment of the requirements for the degree of Masterate of Science in Chemistry at Massey University, New Zealand

Abstract

The research carried out in this thesis comprises an investigation into the synthesis and characterisation of a variety of complexed phosphine-aldehydes, complexed phosphinoporphyrins, and phosphinoferrocene conjugates. The porphyrin and phosphine moieties are linked together via the vinyl group, a product of Wittig chemistry. In general, functionalisation occurs at the β-pyrrolic position of the porphyrin and at the para position of a phenyl group on the phosphine. Chapter One introduces the properties of porphyrins and the triphenylphosphine ligand, as well as a brief review on the types of functionalised triphenylphosphines. A brief review of existing phosphinoporphyrins is also discussed. The proposal for using the vinylic linking group (and hence Wittig chemistry) to connect the porphyrin and the phosphine moieties is also described. Chapter Two outlines the synthesis of the 4-(diphenylphosphino)benzaldehyde (5) ligand, which is a necessary precursor for the Wittig reaction with meso-tetraphenylporphyrin (TPP) phosphonium salt (1). It was discovered that the Wittig reaction of (1) with (5) led to the synthesis of the product of oxidation, phosphinoporphyrin oxide (7), instead of the desired phosphinoporphyrin (6). Therefore an alternative scheme was pursued - complexation before the Wittig reaction. Hence the remainder of the chapter describes both the synthesis and characterisation aspects of five transition metal complexes of (5). These include complexes of gold, ruthenium, tungsten, and platinum. Chapter Three describes the synthesis and characterisation of a variety of novel complexed phosphinoporphyrins, including two bis-phosphinoporphyrin complexes. This was achieved by utilising Wittig chemistry of TPP phosphonium salt (1) with the appropriate complexed phosphine-aldehyde. In each case, optimisation of the Wittig conditions was required in order to obtain the sterically and thermodynamically favoured trans isomer. Chapter Four extends the phosphinoporphyrin chemistry by investigating the synthesis of a novel phosphinoporphyrin trimer. In order to achieve this, a phosphine tris-aldehyde was synthesised. This chapter focuses on the synthesis and characterisation of tris(4-formylphenyl)phosphine oxide (20). The results of the Wittig reaction of (20) with TPP phosphonium salt (1) are also described. Chapter Five demonstrates the versatility of both the Wittig and phosphine chemistry. In this chapter, the synthesis of phosphinoferrocenes via Wittig chemistry is investigated. The ferrocene and phosphine moieties are linked via the vinyl group, in a similar manner as the phosphinoporphyrins. In this case, functionalisation occurs at the para position of a phenyl group of the phosphine to the cyclopentadienyl ring of the ferrocene. A phosphinoferrocene monomer, (24), was synthesised by Wittig reaction of a ferrocene phosphonium salt (22) with (5). Both the synthesis and characterisation of this compound is reported. Also described is the attempted synthesis of a phosphinotrisferrocene via Wittig reaction of (22) with (20). Chapter Six contains a brief summary of the results obtained during this study, and also mentions future research to be pursued in this field of study.