Synthesis and redox behavior of ruthenium(II) 2,3,4,5-tetramethylruthenocenylacetylide and related complexes. Formation of mu-eta(6):eta(1)-[(cyclopentadienylidene)ethylidene]diruthenium complexes containing a strong metal-metal interaction

1-Ethynyl-2,3,4,5-tetramethylruthenocene was prepared by the reaction of 1- formyl-2,3,4,5-tetramethylruthenocene with trimethylsilyldiazomethyllithium and also by the reaction of 1-(2',2'-dichlorovinyl)-2,3,4,5-tetramethylrut henocene, which was obtained from the reaction of 1-formyl-2,3,4,5-tetramet hylruthenocene with lithium dichloromethyldiethylphosphonate and tert-butyl lithium in good yield. 1-Ethynyl-2,3,4,5-tetramethylruthenocene reacted wit h RuClP2L (P-2 = 2 PPh3 or dppe; L = eta-C5H5, eta-C5Me5, or eta(5)-C9H7) i n the presence of NH4PF6 or AgBF4, followed by the column chromatography on deactivated Al2O3, to give Ru(C= CRc')P2L in moderate or good yield. Ru(C= CRc)P-2(eta(5)-C9H7) and Ru(C=CRc*)P-2(eta(5)-C9H7) were similarly prepared (Rc, Rc', and Rc* are ruthenocenyl, 2,3,4,5-tetramethylruthenocenyl, and 1 ',2',3',4',5'-pentamethylruthenocenyl, respectively). The structures of Ru( C=CRc')(dppe)(PPh3)(2)(eta-C5H5), Ru(C=CRc)(dppe)(eta(5)-C9H7), and Ru(C=CR c')(dppe)(eta(5)-C9H7) were determined by X-ray analysis. Cyclic voltammetr y of the acetylide complexes showed two well-separated quasi-reversible wav es. Chemical oxidation of ruthenium(II) 2,3,4,5-tetramethylruthenocenylacet ylide complexes gave products whose stability was dependent on the ligand o n the Ru(II) moiety. The C-13 NMR spectrum of the oxidized species isolated as stable crystals confirmed the structural rearrangement of the bridging acetylide ligand to a mu-eta(6):eta(1)-[(cyclopentadienylidene)ethylidene] ligand. The structure of [(eta-C5H5)Ru(mu-eta(6):eta(1)-C5Me4=C=C)Ru(dppe)( eta(5)-C5Me5)](BF4)(2) was determined by X-ray analysis.