Ruthenium‐Capping of Di‐ and Tetraethynylbiphenyls

The di- and tetraalkynyl biphenyls 3 and 5 have been synthesized from the tetrabromo derivative 1 by using Pd-catalyzed cross-coupling reactions. The reaction of 3 or 5 with cis-[RuCl2(dppe)2] (8) affords vinylidene ruthenium complexes, which were deprotonated with Et3N to give the terminal σ-alkynylruthenium derivatives 9−12. The reaction of 3 or 5 with [Ru(CO)ClH(PPh3)3] (13) gave the corresponding di-σ-alkenyl ruthenium complexes 14 and 15.