Ruthenium Tris(pyrazolyl)borate Complexes, 12 Cross Coupling of Acetylenes with Olefins-Formation of #eta#~3-Butadienyl and #eta#~2-Butadiene Complexes via a Metallacyclobutane Intermediate

摘要

Selective coupling of olefins and terminal acetylenes is shown to be effected in the coordination sphere of Ru~(II) by the successive intermediacy of vinylidene and ruthenacyclobutane complexes. Subsequent deprotonation of one of the #beta#-hydrogen atoms of the latter by NaOEt yields #eta#~3-butadienyl complexes, while in the presence of Cl~- rearrangement takes place to give neutral #eta#~2-butadiene complexes by a #beta#-hydrogen elimination/reductive elimination sequence. [Ru(tp)(COD)Cl] and [Ru(tp){#eta#~30(P,C,C)Ph_2PCH=CH(Ph)=CH_2}Cl] were the starting materials which were treated with HC (ident to) CR (R=Ph, C_6H_9, ferrocenyl, CH_2Ph, nBu). The #eta#~3-butadienyl complexes are nucleophilic at the enynyl carbon atom reacting readily with the electrophiles H~+ and I_2 to give the corresponding #eta#~2-butadienyl complexes. X-ray structures of representative products are given.