- Synthesis of ruthenium half-sandwich complexes by naphthalene replacement in [CpRu(C10H8)]+
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Replacement of the naphthalene ligand in ruthenium complex [CpRu(C 10H8)]+ (1) by halide anions readily proceeds at room temperature to give insoluble oligomeric species [CpRuX]n (X = Cl, Br, I). Similar reactions in the presence of mono- or bidentate ligands afford complexes [CpRuL2X] where L = CO, P(OMe)3, tBuNC; L2 = dppm, dppe, dppp, bipy, phen, cod, nbd, or 1,4- diphenylbutadiene. Useful catalysts [CpRu(cod)X] were obtained by this method in 70-90 % yields. The structure of [CpRu(cod)I] was determined by X-ray diffraction. Reaction of 1 with Br- and allyl bromide afforded RuIV complex [CpRu(η3-C3H 5)]Br2. Cation 1 also was found to react with azide anion in the presence of bidentate phosphanes to afford [CpRuL2N 3] (L2 = dppm, dppe). Reaction of 1 with neutral ligands in the absence of nucleophilic anions proceeded under visible-light irradiation to give cationic complexes [CpRuL3]+ [L = CO, P(OMe) 3, P(OEt)3, tBuNC] in 80-90 % yields. Complex 1 (2 mol-%) catalyzed cyclotrimerization of dipropargyl Meldrum's acid with various alkynes RC≡CH [R = H, Bu, Hex, Ph, SiMe3, (CH2) 4C≡CH, (CH2)3OH, (CH2) 2Br, CH2OMe, CH2OAc, CH2NMeBoc] producing benzene derivatives in 50-85 % yields. According to DFT calculations, the attack of the first ligand (Cl- or L) is a rate-determining step in the naphthalene replacement in 1. The activation barrier for attack of the Cl- anion is ca. 10 kcal mol-1 lower in energy than that of the neutral ligands L = CO, MeNC, MeCN, thus providing a rationale for the faster reaction in the presence of halide anions. The barriers for naphthalene replacement in 1 were also found to be ca. 10-15 kcal mol-1 lower in energy than those for the benzene replacement in [CpRu(C6H 6)]+. The readily available (naphthalene)ruthenium complex 1 was shown to be a convenient precursor for various [CpRuL2X] complexes and an efficient catalyst for the cyclotrimerization of 1,6-diynes with assorted alkynes. Copyright
- Perekalin, Dmitry S.,Karslyan, Eduard E.,Trifonova, Evgeniya A.,Konovalov, Andrew I.,Loskutova, Natalia L.,Nelyubina, Yulia V.,Kudinov, Alexander R.
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p. 481 - 493
(2013/04/10)
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- Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions
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Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(η2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55°C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(η2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(η2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(η2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(η2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolyfic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(η2-H2)complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = O[Tf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of . hydrazido(2-) intermediates such as 19 with H2 at 55 °C was considered to result in the formation of NH3, concurrent with the generation of W(VI)species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten.
- Nishibayashi,Takemoto,Iwai,Hidai
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p. 5946 - 5957
(2008/10/08)
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- Cyclopentadienyl-Ruthenium and -Osmium Chemistry. XXII. Synthesis, X-Ray Structure and Some Reactions of RuCl(PPh3)(η1-Ph2PCH2PPh2)(η-C5H5), Containing a Monodentate CH2(PPh2)2 Ligand
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Stoichiometric amounts of RuCl(PPh3)2(η-C5H5) and dppm react in refluxing C6H6 to give RuCl(PPh3)(η1-dppm)(η-C5H5), which has been fully characterized by an X-ray study (triclinic, space group P, a 22.377(6), b 9.913(2), c 9.826(3) Angstroem, α 70.46(2), β 78.72(2), γ 80.40(2) deg, Z 2) in which 3299 data were refined to R 0.046, R' 0.052.Structural parameters are similar to those of other RuX(PR3)2(η-C5H5) complexes.The chloro complex was converted was converted into 2-dppm)(η-C5H5)>+ salts; the other PPh3 ligand can be replaced by a second dppm ligand to give +, which contains both mono- and bidentate dppm ligands.Alkylation of the uncoordinated phosphorus with Mel is accompanied by halogen exchange to give I, while reactions with a variety of transition metal complexes result in abstraction of PPh3 and formation of RuCl(dppm)(η-C5H5).
- Bruce, Michael I.,Humphrey, Mark G.,Patrick, Jennifer M.,White, Allan H.
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p. 2065 - 2072
(2007/10/02)
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