Aminocarbyne-Alkyne Coupling in Diruthenium Complexes: Exploring the Anticancer Potential of the Resulting Vinyliminium Complexes and Comparison with Diiron Homologues.

New diruthenium complexes based on the scaffold Ru 2 Cp 2 (CO) 2 (Cp = η 5 -C 5 H 5 ) and containing a bridging vinyliminium ligand, [ 2a - d ]CF 3 SO 3 , were synthesized through regioselective coupling of alkynes with an aminocarbyne precursor (85-90% yields). The reaction involving phenylacetylene proceeded with the formation of a diruthenacyclobutene byproduct, [ 4 ]CF 3 SO 3 (10% yield). Complexes [ 2a - d ] + undergo partial alkyne extrusion in contact with alumina or CDCl 3 . All products were characterized by elemental analysis, infrared and multinuclear NMR spectroscopy, and single crystal X-ray diffraction in two cases. Complexes [ 2a - d ] + revealed an outstanding stability in DMEM cell culture medium at 37 °C (<1% degradation over 72 h). These complexes exhibited cytotoxicity in human colon colorectal adenocarcinoma HT-29 cells in the low micromolar range, with lower IC 50 values than those obtained with the homologous diiron complexes previously reported. Evaluation of ROS (reactive oxygen species) production and O 2 consumption rate (OCR) highlighted the higher potential of Ru 2 complexes, compared to the Fe 2 counterparts, to impact mitochondrial activity, with the heterometallic Ru 2 -ferrocenyl complex [ 2d ] + showing the best performance.