Methylene, ruthenium complex

Intermolecular enyne metathesis has recently been developed using ethylene gas as the alkene [20]. The plan is shown in Scheme 10. In this reaction,benzyli-dene carbene complex 52b, which is commercially available [16b], reacts with ethylene to give ruthenacyclobutane 73. This then converts into methylene ruthenium complex 57, which is the real catalyst in this reaction. It reacts with the alkyne intermolecularly to produce ruthenacyclobutene 74, which is converted into vinyl ruthenium carbene complex 75. It must react with ethylene, not with the alkyne, to produce ruthenacyclobutane 76 via [2+2] cycloaddition. Then it gives diene 72, and methylene ruthenium complex 57 would be regenerated. If the methylene ruthenium complex 57 reacts with ethylene, ruthenacyclobutane 77 would be formed. However, this process is a so-called non-productive process, and it returns to ethylene and 57. The reaction was carried out in CH2Cl2 un-... 

CF3H, Methane, trifluoro-cadmium complex, 24 55 mercury complex, 24 52 CF3NOS, Imidosulfurous difluoride, (fluorocarbonyl)-, 24 10 CH2, Methylene ruthenium complex, 25 182 CH2CI4P2, Phosphine, methylenebis-(dichloro)-, 25 121 CH3, Methyl cobalt complexes, 23 170 mercury complexes, 24 143-145 platinum complex, 25 104, lOS CNO, Cyanato silicon complex, 24 99 CN2OS2, l,3k, 2,4-Dithiadiazol-5-one, 25 53 CO, Carbon monoxide chromium complexes, 21 1, 2 23 87 cobalt complex, 25 177 cobalt, iron, osmium, and ruthenium complexes, 21 58-65 cobalt-osmium complexes 25 195-197 cobalt-ruthenium cluster complexes, 25 164... 

However an unexpected new cyclic ruthenium phosphorus ylide half-sandwich complex 42 has been obtained by reaction of 41 with dichloromethane as solvent [79]. The cyclisation involves a C-Cl activation and corresponds to the incorporation of the methylene moiety in the P-C bond and to the ortho-metal-lation of one phenyl of the phosphine. An other novel unusual phosphonium ylide ruthenium complex 43 has also recently been described [80]. 

Ruthenium complexes have been described that are active both in the ROMP reaction and in a subsequent hydrogenation step (30). These catalysts have the pyrimidin moiety incorporated, for example, (l,3-diisopropyltetrahydropyrimidin-2-ylidene) (ethoxy-methylene) (tricyclohexylphosphine) ruthenium dichloride. 

Moreno-Manas et al. [98] reported on a similar effect of triphenylphosphine for the Michael addition of active methylene compounds to n-acceptor olefins such as methyl vinyl ketone, acrylonitrile, and 2-vinylpyridine and dialkyl azodi-carboxylates. They compared the reactivity of RuH2(PPh3)4, RuCl2(PPh3)3, and PPh3 and concluded that for /5-diketones, ketoesters, and ketoamides, triphenylphosphine released from the ruthenium complexes contributes totally or partially to the catalysis. 

Bis(arene) ruthenium complexes (99) + are electrophilic and add various nucleophiles (see Nucleophile), including hydride, to form (100) (Scheme 24). Methyl groups of methylated arene rings are acidic and can be deprotonated, giving the corresponding exo-methylene complexes (101). This is similar to the chemistry developed for analogous iron complexes, and is reminiscent of the a-mthenocenyl carbonium ions (Section 4.5). 

Platinum and palladium complexes of thietane and 3,3-dimethylthietane have been prepared as illustrated for 90. The platinum complexes exist in cis and trans configurations, but no cis-trans isomerization of the palladium complexes in the solid state was observed. Stability constants of thietane with Mn(ll), Co(II), and Ni(II) chelates have been determined. Proton nmr studies show that the absorption of the a-methylene protons, which are syn to the metal, is shifted downfield (about 0.7 ppm) more than the absorption of the protons anti to the metal (about 0.4 ppm downfield). Energies of activation for pyramidal inversion were determined. Bis-ruthenium complexes of di-, tri- and tetraspirothietanes (e.g., 90a) show rapid electron transfer between the ruthenium ions long-range electron tunneling was proposed. ... 

A unique asynunetric isomerization of 2-substituted 5-methylene-l,3-diox-anes 22 to 5-methyl-4H-l,3-dioxins 23 was catalyzed by a ruthenium complex of DIOP under a hydrogen atmosphere (Scheme 3). Although the enantiomeric purity remained in the range of 35 to 50%, cyclic acetals obtained are promising starting materials for the synthesis of macrolide antibiotics and other polyketide-derived natural products [30]. 

Among the other reduced prochiral substrates, methylene succinic acid was hydrogenated with ee values up to 59 and 50% using respectively the catalysts Rh-3 [3] and Ru-BINAP (9) [21]. The hydrogenation of the /hketo ester 21 was also performed in water in the presence of ruthenium complexes associated with ligands 13 and 14 (Eq. 4) [24, 25] the hydroxy ester 22 was obtained with enantioselectivi-ties up to 94%. 

The ruthenium complexes were attached to the specified cysteine by formation of a thioether linkage between the sulfur atom of cysteine and the methylene carbon of one of the bipyridine ligands. The reaction makes use of complexes that contain 4-bromomethyl-4 -methylbipyridine, as indicated. 

Z)-Enol esters. The stereoselective addition of carboxylic acid to a terminal alkyne linkage is catalyzed by ruthenium complexes. Bidentate phosphine ligands separated by 2, 3, or 4 methylene groups are all effective. 

The photoreduction of 1 by triethylamine occurs in a variety of solvents including isobutyronitrile, THF, acetonitrile-isopropyl alcohol, methylene chloride, and chloroform although the reaction does not appear to be clean or to go to completion in the latter two solvents. Quantum yields measured thus far are 0.35, 0.2, and 0.05 in dry acetonitrile, isobutyronitrile, and THF, respectively. Although the reduced ruthenium complex, RuLs, is stable on a time scale of minutes to hours, we find that the pre-irradiation spectrum of RuLs is slowly regenerated on a time scale of hours to days in degassed solutions allowed to stand in the dark at 20°-25°C. Admission of air to the samples results in instantaneous regeneration of the spectrum of RuLs. As mentioned above, the overall reaction sequence appears best described by Reactions 9, 14, and 16 as outlined below. This predicts a limiting quantum yield of two for... 

The isolation of a diamagnetic bridging methylene complex [(OEP-N-yx-CH2) Ru(CH3)](BF4) from decomposition of [(OEP - N - CH3)Ru(CH3)](BE4) was also possible. This complex has been characterized by H NMR and partially by an X-ray structure [145]. Unfortunately, reduction of this complex did not result in formation of an axial methylene carbene complex as was postulated by James and Dolphin [146]. Although M = CH2 species have been prepared [147,148], similar metalloporphyrin complexes are not yet known. Ruthenium carbene complexes which are involved in catalytic reactions will be discussed below. 

C, Carbide, iron complex, 26 246 ruthenium cluster complexes, 26381-284 CHF3O3S, Methanesulfonic add, trifluoro-, iridium, manganese, and rhenium com-iriexes, 26 114,115,120 platinum complex, 26 126 CHOS2, Dithioaubonic add, 27 287 CH2> Methylene, osmium complex, 27 206 CH2O2, Formic add, rhenium complex, 26 112... 

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