The work described in this thesis is a study of iron-sulphur-nitrosyls and related compounds. Chapter One is an introduction to the work presented. Chapter one is introduction to the work presented. Chapter Two is concerned with the analogous Fe2(SR)2(CO)6 and its conversion to Fe2(SR)2(NO)4. Chapter Three is concerned with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 and [Fe4X3(NO)7] (X=S, Se). Chapter four is concerned with an e.p.r. examination with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 [Fe4X3(NO)7] (X=S,Se). Chapter four is concerned with an e.p.r. examination of Fe2(SR)2(NO)4 and bridging ligand exchange reactions. Chapter Five is concerned with a similar examination of Fe2I2(NO)4.Chapter six is concerned with an examination of ligand exchange processes in Fe4S4(NO)4 and [Fe4S4(NO)4]. Chapter Seven is concerned with an investigation of iron-sulphur protein models and their conversion to iron-nitrosyls.