Reaction of a permetallated ethene, (mu4-C=C)Fe2R-mu2Cp*2(CO)10, with diphenylacetylene affords the adduct with a new C2-binding mode, a mu4-dicarbyne complex, (mu4-C-C)Fe2Ru2Cp*2(CO)6(mu-Ph-C[triple bond]C-Ph), containing a dimetallacyclobutariene core.
A tetranuclear C2 (dicarbide) cluster complex with a permetallated ethene structure, (μ4-CC)Ru2(FeCp*)2(CO)10 (2), reacts with alkynes in refluxing THF to give a variety of adducts resulting from
C−C coupling and oxidative metallacyclization with the C2 ligand in addition to a unique μ4-dicarbyne
complex with a dimetallacyclobutatriene core, (μ4-C−C)Ru2(FeCp*)2(CO)6(μ-η2:η2-PhC⋮CPh). The
reactions are initiated by decarbonylation, as confirmed by the reactions of an isolated, labile species
lightly stabilized by MeCN, (μ4-CC)Ru2(FeCp*)2(CO)8(NCMe)2, which undergoes the reactions at room
temperature and provides the same types of products as those obtained from 2.
A series of di- and trinucleating ligands with a 1,3,5-triethylbenzene core connected to N,N-bidentate tethers was synthesized. The ligands readily reacted with monuclear Rh and Pd precursors to give the corresponding di- and trinuclear complexes, which were characterized by using NMR and ESI mass spectroscopy. In the solid state, the trinuclear complexes with ligands having pyridylpyrazolyl tethers adopt the most stable ababab configuration, in which the organometallic fragments are on the same side of the benzene plane. On the other hand, in solution, the linker moieties between the benzene core and the metals are flexible enough to interconvert between other configurations, that is, they exhibit dynamic behavior, and the rotational barrier was dependent on the length of the linkers. From variable temperature (VT) 1H NMR measurements, the rotational barrier for a trinuclear Rh-CO complex with a ligand having methylene linkers was estimated to be approximately 12.6 kcal mol(-1). However, no spectral changes were observed for the ethylene derivative in the temperature range of -60 degrees C to 50 degrees C, indicating that the rotation was not frozen out on the 1H NMR timescale, even at -60 degrees C.
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