Five aminophosphine complexes of Ru(II) have been prepared as potential chemotherapeutic agents and characterised by NMR and X-ray crystallography. The chelate ring-opening process of the bidentate aminophosphine ligand in the complex cis, trans-[Ru(H₂NCH₂CH₂PPh₂-N,P)₂Cl₂ has been investigated by 2D NMR methods. The complex undergoes a ring-opening reaction in coordinating solvents via the cleaving of the Ru-N bond. This exposes a potential binding site on the metal, and leads to the possibility of in vivo reactivity. A range of water-soluble Ru(II)arene complexes of the type [(h⁶-arene)Ru^IIX(L-L)]^- [(h⁶-arene)Ru^IIX(L)₂]^- and [(h⁶-arene)Ru^IIX₂L], arene = benzene, p-cymene, alkylbenzoate, biphenyl, L-L = ethylenediamine, L = acetonitrile, isonicotinamide, X=Cl, Br, I, have been synthesised with an aim to produce anticancer active agents. They have been characterised by NMR and X-ray crystallography. The hydrolysis of [(h⁶-p-cymene)Ru^IICl(en)]⁺ and [(h⁶-biphenyl)Ru^IICl(en)]⁺ has been followed by HPLC and ESI-MS and an HPLC assay developed for use in studies relating to biological testing. The reactions of a range of Ru(II)arene complexes with the nucleotides 5'GMP, 5'CMP, 5'AMP and 5'TMP have been investigated by NMR. The complex [(h⁶-p-cymene)Ru^IICl(en)]⁺ binds to 5'GMP at the N⁷ of the guanine moiety. On reaction with a 14mer duplex oligonucleotide of known sequence it was found to lower the melting temperature of the duplex significantly to a level comparable to cisplatin. The complex forms mono and bis adducts with the oligonucleotide in a guanine specific manner, as elucidated by HPLC separation, ESI mass spectrometry and enzymatic digestion. Cytotoxic studies on Ru(II) compounds revealed a significant effect against the ovarian cancer cell line A2780. Cross resistance studies indicate that the complex [(h⁶-p-cymene)Ru^IICl(en)]⁺ is influenced by the protein p53, but ([h⁶-biphenyl)Ru^IICl(en)]⁺ possibly functions as an inhibitor of topoisomerases.