184840-11-7Relevant academic research and scientific papers
Ruthenium-catalyzed dimerization of terminal alkynes initiated by a neutral vinylidene complex
Slugovc, Christian,Mereiter, Kurt,Zobetz, Erich,Schmid, Roland,Kirchner, Karl
, p. 5275 - 5277 (1996)
The complexes RuTp(PPh3)2Cl (1) and RuTp-(PPh3)(Py)Cl (2) catalyze the dimerization of HC≡CR, where R = Ph, SiMe3, n-Bu, and t-Bu, to give 1,4- and 2,4-disubstituted butenynes with both conversion and selectivity strongly depending on the alkyne substituent, where the catalytic precursor is the neutral vinylidene complex RuTp(PPh3)(Cl)(=C=CHR). The hydride complex RuTp(PPh3)2H (3) exhibits the same catalytic activity as 1 and 2.
Ruthenium(II) tris(pyrazolyl)borate complexes. Reversible vinylidene complex formation
Slugovc, Christian,Sapunov, Valentin N.,Wiede, Petra,Mereiter, Kurt,Schmid, Roland,Kirchner, Karl
, p. 4209 - 4216 (1997)
A convenient high-yield route to [Ru{HB(pz)3}Cl(PPh3)(=C=CHR)] (pz = pyrazolyl; R = Ph, SiMe3, Bun, But, CO2Et or C6H9) has been found through the intermediary [Ru{HB(pz)3}Cl(PPh3)(dmf)] (dmf = dimethylformamide) which has been crystallographically characterized. This complex is readily obtained on treatment of [Ru{HB(pz)3}Cl(cod)] (cod = cycloocta-1,5-diene) with 1 equivalent of PPh3 in boiling dmf. The vinylidene moiety in complexes of the type [Ru{HB(pz)3}Cl(PPh3)(=C=CHR)] is remarkably labile being easily replaced by nucleophiles L = PMe3, PPh3, MeCN, pyridine or CO to give [Ru{HB(pz)3}Cl(PPh3)L]. With the exceptions of L = PMe3 or CO, these reactions are reversible. The complex [Ru{HB(pz)3}Cl(PPh3)(CO)] has been characterized by X-ray crystallography. On treatment of [Ru{HB(pz)3}Cl(PPh3)(=C=CHPh)] with an excess of HC=CR′ (R′ = SiMe3, Bun, But, CO2Et or C6H9) the neutral vinylidene complex [Ru{HB(pz)3}Cl(PPh3)(=C=CHR′)] was reversibly formed. Comparative studies and extended-Hueckel molecular orbital calculations have been performed to elucidate the nature of the bonding in the various vinylidene complexes. The bonding between the metal center and the vinylidene ligand is dominated by the dyz (metal)-p (vinylidene) interaction. If this contribution is small, reconversion of the vinylidene complex into an η2-alkyne complex can be accomplished.
Reactivity of [TpRuCl(PTA)(PPh3)] with alkynes and propargylic alcohols: Occurrence of structurally related cationic vs neutral allenylidene complexes with the ruthenium hydrotris(pyrazolyl)borate moiety
Bolano, Sandra,Mar Rodriguez-Rocha,Bravo, Jorge,Castro, Jesus,Onate, Enrique,Peruzzini, Maurizio
, p. 6020 - 6030 (2009)
[TpRuCl(PTA)(PPh3)] (1; PTA = l,3,5-triaza-7-phosphaadamantane) reacts with phenylacetylene, yielding the alkynyl complex [TpRu(C≡CPh) (PTA)(PPh3)] (2) or the neutral vinylidene complex [TpRuCl{C=C(H)Ph}(PTA)] (4), depending on the solvent and the reaction conditions (Tp = hydrotris(pyrazolyl)borate). Protonation of 2 with HOTf(OTf = OSO2CF3) in CH2Cl2 yields the dicationic vinylidene compound [TpRu{C=C(H)Ph}{PTAH}(PPh3)](OTf) 2 (3), bearing a N-protonated PTA ligand. Reaction of 1 with 1,1-diphenyl-2-propyn-l-ol affords the new cationic compound [TpRu(C=C=CPh 2)(PTA)(PPh3)]PF6 (5) or neutral allenylidene compound [TpRuCl(C=C = CPh2)(PTA)] (6), depending on the reaction solvent (MeOH or toluene, respectively). The reactivity of complexes 5 and 6 toward tertiary phosphines (PTA and PPh2Me) has been investigated. Remarkably, both the cationic and the neutral allenylidene compounds undergo regioselective nucleophilic attack at the allenylidene Ca position to give the cr-allenyl-phosphonium complexes [TpRu{C(L)=C=CPh2}(PTA)(PPh 3)]PF6 (L = PPh2Me (8), PTA (9)) and [TpRuCl{C(L)= C=CPh2)(PTA)] (L = PTA (10), PPh2Me (11)), respectively. Noticeably, the reaction goes to completion in the case of the neutral allenylidene complex 6, whereas an equilibrium between the phosphonioallenyl adduct and the educt species is observed in the case of the cationic allenylidene compound 5. The thermodynamic parameters for such an equilibrium have been determined by NMR methods at different temperatures. Finally, the hydrolysis of the neutral allenylidene 6 has been briefly considered, showing the formation of the carbonyl compound [TpRuCl(CO)(PTA)] (7).
