This thesis describes a p-H2 based NMR study of the reactivity cif the 'precursor-receptor' complexes, [IrI(CO)(dppe)], [RhCl(C2Ht)(pCY3)2], [IrCl(CO) {P(P-(tolyl)3h], [IrCh(H) {P(P-(tolyl)3h], [IrCl(DMSO)3] and [IrCl(CO)2{P(o-(tolyl)3}] towards a number of biological molecules and H2. In this study the characterisation of low concentrations of metal-amino acid, and metalnucleobase species has been achieved using the enhancement power ofp-H2. 'Precursorreceptor' complexes as described in this thesis, can simultaneously bind H2 and a suitable donor function from a biological molecule. The use ofp-H2 ensures that these products and detected at optimal sensitivity. It is shown that substrate addition to the 'precursor-receptor' [IrCl(CO)(H)2 {P(P-tolyl)3h], occurs at the expense of loss of the carbonyl ligand. It has been therefore possible to characterise [IrCl(H)2 {(P-p-tolyl)3h] based addition products containing pyridine, amino acids, and nucleobases; all of these materials are present in such low concentrations that they would not be normally seen. The hydride signals of these species are diagnostic of the substrate molecule. The power of p-H2 enhancements allowed the acquisition of 15N chemical shift data for these complexes without the need for enrichment. The 'precursor-receptor' complex [IrCh(H){(P(P-tolyl)3}3] readily reacts with pyridine and form isomers of [IrCh(H)(py) {(P(P-tolyl)3} 2] at the expense of the labile phosphine ligand. [IrCh(H){(P(p-tolyl)3h] reacts withp-H2and pyridine to form [IrCl(H)2(py)(P(p-tolyl)3)2]. Surprisingly, [IrCl(DMSO)3] reacts with amino acids to form monohydride-containing amino acid adducts where the hydride signals are again of the substrate molecule. These results were significant step ofthe goals of the research project.