The present invention relates to a transition metal complex represented by Formula (I) or salts thereof, or to a ligand represented by Formula (H) or salts thereof, wherein X represents a transition metal, preferably Pt, and methods for their use and preparation. In particular, the invention relates to compounds which may possess useful therapeutic activity in treating amyloid diseases, and in particular, Alzheimer's disease. The invention also relates to the use of these compounds in methods of therapy, and diagnosis, and the manufacture of medicaments as well as compositions containing these compounds.