This thesis consists of three closely related areas of study. The first chapter describes a brief history of organometallic chemistry which leads onto the use of phosphine/ diphosphine ligands in organometallic compounds. The second chapter concerns the use of para-ethynylaniline as a building block towards the synthesis of large linear molecules in which transition metal centres are linked via a fully -conjugated backbone. Two crystal structures were obtained, namely trans-[Pt(PPh3)2(C≡CC6H4NH2)2]and [(μ-H)Ru3(CO)9(μ3-C≡CC6H4NH2)]. The third chapter is about the synthesis of a range of supramolecular structures based on the use of functionalised acetylides, linked by silver ions. These have been probed by X-ray crystallography and three crystal structures, trans-[PtAg (C≡CCH2CH2OH)2(PMe2Ph)2]n[ClO4]n(MeCN)n, trans-[PtAg(C≡CPh)2(PMe2Ph)2]n [ClO4]n and trans-[PtAg2{C≡CC(CH3)2OH}2(MeCN)4(PPh3)2][ClO4]2 were determined. The final chapter describes the systematic synthesis of a number of small bite- angle diphosphine complexes and again X-ray crystallography has been used to probe the bite angle and its effect on the coordination sphere of the metal centre. A number of crystal structures of the type [M(CO)4{η2-(o-tolyl)2PCHRP(o-tolyl)2}] (R = H, Me, Et, CH2Ph; M = Cr, Mo, W) were obtained.