Iridium piano stool complexes with activity against S. aureus and MRSA: it is past time to truly think outside of the box.

A new class of piano-stool iridium complexes with 1,2-diaminoethane ligands are shown to be effective and safe antimicrobials with activity against Staphylococcus aureus, including various isolates of methicillin-resistant strains (MRSA). Comparison to other piano stool complexes with activity against mycobacteria are made along with a discussion of structure-activity relationships. The structures of one the most active complexes with the ligand cis-1,2-diaminocyclohexane and one of the least active complexes with the ligand trans-1,2-diaminocyclohexane are compared and discussed with respect to their drastically different activities. In vitro toxicity studies for all of the complexes are described. In addition, a mouse study with one of the complexes, [(pentamethylcyclopentadienyl)(cis-1,2-diaminocyclohexane)(chloro)iridium]chloride, showed no ill effects on the mice at high doses.