Reactivity of 17 e− Complex [ReIIBr4(CO)2]2− with Bridging Aromatic Ligands. Characterization and CO-Releasing Properties

Abstract

Carbon monoxide releasing molecules (CO-RMs) are a newly emerging class of compounds of pharmacological interest. Among the transition metal-based CO-RMs, 17-electron complexes of general formula cis-trans-[Re^II(CO)₂Br₂L₂] are promising candidates but their poor hydrophilicity hampers future applications. In an effort to increase water solubility of d⁵ dicarbonyl rhenium CO-RMs, the reaction of the cis-[Re^II(CO)₂Br₄]²⁻ anion with bridging aromatic ligands of the pyridine and diazine type was investigated. Mononuclear and binuclear complexes are presented and it is shown that the nature of the bridging ligand critically dictates the formation of either species. Most complexes retained their fundamental CO-releasing properties. The synthesis of the molecules together with structural, spectroscopic and theoretical details are discussed.