Platinum and Gold Complexes with Unusual Oxidation States and Their Potential Role in Anticancer and Therapeutic...

Transition metal complexes featuring unusual oxidation states represent an exciting frontier in inorganic chemistry. This review surveys the unusual oxidation states of two biologically important metals, platinum (Pt^I and Pt^III) and gold (Au^II), examining their electronic structures, bonding characteristics, and biomedical relevance, among other features. Emphasis is placed on synthetic strategies, redox behavior, and factors influencing their stability and stabilization. Pt^III complexes can potentially offer an alternative to the traditional Pt^II/IV anticancer chemotherapy framework and be an intermediate in Pt^II/IV redox chemistry. Indeed, the Pt^III-based platinum blues have been widely investigated as anticancer agents soon after the landmark discovery of cisplatin as a cancer chemotherapeutic. Au^II complexes are less explored for their biological properties but may be intermediates in Au^I/III redox chemistry and offer an alternative pathway to gold-based chemotherapeutics. We outline current challenges and future directions in this evolving field, where fundamental chemistry meets therapeutic innovation.