Tertiary Imidazole Phosphine Ligands and Their Transition Metal Complexes

Abstract

<p>Gold(I) phosphine complexes have been used in the treatment of rheumatoid arthritis. One such complex, auranofin (triethylphosphinegold(I)2,3,4,6-tetra-O-acetyl-1-thio-$\beta $-glucopyranoside) is a commercially available drug. It is possible to replace the triethylphosphine by other phosphines, hence changing the chemical and physical properties of the compounds. Tertiary imidazole phosphines are multidentate ligands containing both "soft" and "hard" binding sites. By use of such ligands, it is possible to make complexes that can bring two different metal ions into the biological system at once.</p> <p>In this work, a number of tertiary imidazole phosphine ligands and their metal complexes have been prepared and characterized by the X-ray diffraction method and other spectroscopic methods. The chemical properties of the phosphine ligands have been investigated.</p> <p>The phosphines which have the phosphorus atom connected to the C2 carbon atom of the imidazole ring are poor $\sigma$-bases with respect to the phosphorus atom and are subject to chemical attack in the presence of some metal cations. Complexes of these ligands with hard or soft metal ion have been obtained, but no complexes with both a hard and a soft metal ion have been isolated for these phosphines. A new phosphine with the phosphorus atom connected to the C5(4) carbon atom of the imidazole ring has been synthesized, which readily binds to both hard and soft metal ions. A complex of this ligand with gold(I) and copper(II) has been prepared and characterized.</p> <p>Some gold(I) and platinum(II) complexes with ligands related to the decomposition products of the tertiary imidazole phosphines have also been prepared and characterized. The dynamic and static Jahn-Teller effects of the copper(II) complexes studied in this work are discussed.</p>