The preparation of dithiadiazolyl and diselenadiazolyl complexes of platinum and palladium

Abstract

This thesis describes the reaction of phenyl dithiadiazolyl, [PhCNSSN], and phenyl diselenadiazolyl, [PhCNSeSeN], with zero-valent phosphine complexes of platinum and palladium. Chapter one outlines the experimental techniques utilised to prepare and characterise the compounds prepared during the course of this research and contains techniques solely employed within the laboratory that this research was undertaken. The second chapter describes the chemistry of dithiadiazolyls and an improved synthetic route to the ligand [PhCNSSN].The third chapter outlines the chemistry of platinum and palladium and also describes the synthesis of the platinum and palladium complexes used throughout this project. Chapter four describes the reaction of [Pt(PPh(_3))(_4)], [Pt(dppe)(_2)] and [Pd(dppe)(_2)] with [PhCNSSN] to form the novel monometallic complexes [Pt(SNC(Ph)NS-S,S)(PPh(_3))(_2)], [Pt(SNC(Ph)NS-S,S)(dppe)] and [Pd(SNC(Ph)NS-S,S)(dppe)]. These complexes have been extensively studied by x-ray crystallography, magnetic measurements, e.s.r. and u.v./vis spectroscopy. The biological activity of [Pt(SNC(Ph)NS-S,S)(PPh(_3))(_2)] and m.o. calculations on [Pt(SNC(H)NS-S,S)(PH(_3))(_2)] were used as a basis for further study. In chapter five the formation of trimetallic dithiadiazolyl complexes from the reaction of [PhCNSSN] with zero-valent phosphine complexes has been described. [Pt(_3)(µ(_s-s)SNC(Ph)NS)(_2)(PPh(_3))(_4)], [Pt(_3)((µ_S-s)SNC(3,4FC(_6)H(_3))NS)(_2)(PPh(_3))(_4)] and [Pd(_3)(µ(_s-s)SNC(Ph)NS)(_2)(PPh(_3))(_4)] have been structurally characterised. The unique type of bonding in these species has been described with the aid of m.o. calculations undertaken on [Pt(_3)(µ(_s-s)SNC(H)NS)(_2)(PH(_3))(_4)].Chapter six describes the decomposition of monometallic to trimetallic dithiadiazolyl complexes with the varying stabilities of different monometallic species rationalised; kinetic measurements made and a mechanism for the decomposition is proposed. N.m.r. and e.s.r. spectroscopy has been used to observe other decomposition products formed. Chapter seven examines the oxidative decomposition of monometallic dithiadiazolyl complexes electrochemically (by cyclic voltammetry) and chemically (by reaction with NOBF(_4)). The reaction between [Pd(SNC(Ph)NS-S,S)(dppe)], NOBF(_4) and trace moisture results in the formation of a novel dimetallic species [Pd(_2)(µ(_s-s)NC(Ph)N(H)S)(dppe)(_2)] which has been structurally characterised. Finally, chapter eight outlines an improved synthetic route to (PhCNSeSeN)(_2) and the frozen glass e.s.r. spectrum of [PhCNSeSeN]. Reaction between [PhCNSeSeN] and [Pt(PPh(_3))(_4)] has resulted in the formation of [Pt(SeNC(Ph)NSe-Se,Se)(PPh(_3))(_2)] and reaction between [PhCNSeSeN] and [Pd(PPh(_3))(_4)] has resulted in the formation of [Pd(_3)(µ(_se-se)NC(Ph)NSe)(_2)(PPh(_3))(_4)]