Rapid Access to Derivatized, Dimeric, Ring-Substituted Dichloro(cyclopentadienyl)rhodium(III) and Iridium(III) Complexes

The present work describes the design and synthesis of a series of rhodium and iridium dimers [(η5-ring)­MCl]2(μ2-Cl)2 (where (η5-ring)­MCl = (η5-Me4C5R)­Rh­(III)Cl or (η5-Me4C5R)­Ir­(III)­Cl) using a new and efficient 1 h procedure. Rhodium and iridium dimeric complexes were synthesized via a microwave reaction. The modified HMe4C5R (R = isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, phenyl, benzyl, phenethyl, cyclohexyl, and cyclopentyl) type ligands were synthesized by reaction of 2,3,4,5-tetramethylcyclopent-2-en-1-one with the respective Grignard reagent (RMgX), followed by elimination of water under acidic conditions to produce the tetramethyl­(alkyl or aryl)­cyclopentadienes in moderate to excellent yields (40–98%). Reaction of the HMe4C5R ligands with [M­(COD)]­(μ2-Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) gave the dimeric complexes [(η5-Me4C5R)­MCl]2(μ2-Cl)2 in yields ranging from 47% to 96%. The derivatized dimers were tested for antimicrobial activity, showing activity against Mycobacterium smegmatis and improved activity with derivatized R groups against Staphylococcus aureus and MRSA 43300. The characterization of these complexes was completed by NMR spectroscopy, single-crystal X-ray diffraction, high-resolution mass spectrometry, and elemental analysis.