| Abstract
| - A series of cationic vinylidene complexes of the type [TpRuCCHR(PR3)2][BPh4] (Tp =hydrotris(pyrazolyl)borate; PR3 = PEt3, PMeiPr2; R = Ph, But, COOMe) have been prepared.The reaction of [TpRuCCHCOOMe(PEt3)2][BPh4] with a further HC⋮CCOOMe moleculeyields the E-stereoisomer of the vinylvinylidene derivative [TpRuCC(COOMe)CHCHCOOMe(PEt3)2][BPh4], which has been structurally characterized. This C−C couplingreaction has been interpreted in terms of a [2 + 2] cycloaddition of the alkyne to the Cα−Cβbond of the vinylidene ligand to yield a cyclobutenylidene intermediate, followed by aconcerted ring opening. The neutral σ-η1-butadienyl complex [TpRu(CHC(COOMe)CHCHCOOMe(PEt3)2] was prepared by reaction of the vinylvinylidene complex with NaBH4 inMeOH. The reaction of [TpRuCl(PMeiPr2)2] with 1-alkynes leads to neutral vinylidenederivatives [TpRuCCHR(Cl)(PMeiPr2)] (R = Ph, But, SiMe3, H). These complexes reactwith LDA and diphenylacetylene yielding the enynyl species [TpRu(PhCC(Ph)C⋮CR)(PMeiPr2)] (R = Ph, But). These complexes, which were isolated and characterized, areefficient catalysts for alkyne dimerization reactions, as well as for cross-coupling reaction ofterminal alkynes.
- [TpRuCCHCOOMe(PEt3)2][BPh4] reacts with a further HC⋮CCOOMe molecule yielding the E-stereoisomer of the vinylvinylidene derivative [TpRuCC(COOMe)CHCHCOOMe(PEt3)2][BPh4], which has been structurally characterized; the neutral vinylidene derivatives [TpRuCCHR1(Cl)(PMeiPr2)] (R1 = Ph, But) react with LDA and PhC⋮CR2 (R2 = Ph, H) yielding the enynyl species [TpRu(PhCC(R2)C⋮CR1)(PMeiPr2)], which are efficient catalysts for the dimerization as well as for cross-coupling reactions of terminal alkynes.
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