Hydrocarbon complexes of iron, ruthenium, and osmium. Part VII. Complexes of bicyclo-octatetraenyl: crystal and molecular structures of [Ru3(CO)6(C16H14)] and [Fe(CO)2(C16H14)]
Abstract
A minor product from the reaction of [Ru3(CO)12] with phenylcyclo-octatetraene has been identified by X-ray diffraction study as the complex [Ru3(CO)6(C16H14)], containing a bicyclo-octatetraenyl ligand attached to an [Ru3(CO)6] cluster. One of the C8 rings has a bis-η3-allyl attachment to two metal atoms. With two formally bridging carbon atoms, one of which is also involved in bonding to the remaining ruthenium atom. The other ring is 1,5-η4-diene-bonded to this ruthenium atom, with the C8 group in a ‘tub’ conformation. The complex is best obtained (80%) directly from bicyclo-octateraenyl and [Ru3(CO)12] heated under reflux in toluene. Cleavage of bicyclo-octatetraenyl occurs on reaction with iron carbonyls, yielding known iron complexes of cyclo-octatetraene. Other products are the bicyclo-octatetraenyl complexes [Fe(CO)3(C16H14)] and [Fe(CO)2(C16H14)]. A single crystal X-ray diffraction study of the latter reveals a central planar 1,3-diene fragment, incorporating both rings, bonded to the iron atom, while one of the rings adopts a ‘tub’ conformation which enables it to make a further η2 attachment. The co-ordination around the iron atom is distorted trigonal bipyramidal. Treatment of [Fe(CO)2(C16H14)] with L(CO or PPh3) yields [Fe(CO)2(L)(C16H14)], containing presumably bidentate bicyclo-octatetraenyl. Reaction of bicyclo-octatetraenyl with [Os3(CO)12] gave [Os(CO)2(C16H14)] in low yield, while [{Ru(SiMe3)(CO)4}2] afforded fluxional [Ru2(SiMe3)2(CO)4(C16H14)].
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