The present work describes the design and synthesis of a series of rhodium and iridium dimers [(η 5ring)MCl] 2 (μ 2 -Cl) 2 (where (η 5 -ring)MCl = (η 5 -Me 4 C 5 R)Rh-(III)Cl or (η 5 -Me 4 C 5 R)Ir(III)Cl) using a new and efficient 1 h procedure. Rhodium and iridium dimeric complexes were synthesized via a microwave reaction. The modified HMe 4 C 5 R (R = isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, nheptyl, 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 HMe 4 C 5 R ligands with [M(COD)](μ 2 -Cl) 2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) gave the dimeric complexes [(η 5 -Me 4 C 5 R)MCl] 2 (μ 2 -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.