Ruthenium tris activated

Photocatalytic enantioselective oxidative arylic coupling reactions have been investigated by two different groups. Both studies involved the use of ruthenium-based photocatalysts [142, 143]. In 1993, Hamada and co-workers introduced a photostable chiral ruthenium tris(bipyridine)-type complex (A-[Ru(menbpy)3]2+) 210 possessing high redox ability [143]. The catalytic cycle also employed Co(acac)3 211 to assist in the generation of the active (A-[Ru(menbpy)3]3+) species 212. The authors suggested that the enantioselection observed upon binaphthol formation was the result of a faster formation of the (R)-enantiomer from the intermediate 213 (second oxidation and/or proton loss), albeit only to a rather low extent (ee 16 %) (Scheme 54). 

Ruthenium tris-2,2 -bipyridine complexes are known to play an active role as photochemical redox agents in the solar energy conversion The corresponding amphiphilic complex 96 does not polymerize, presumably due to sterical reasons. The Ru ions are octahedrally coordinated by the three 2,2 -bipyridine ligands, which causes a very bulky size of the head group. As a consequence, the distances between adjacent diyne units likely become too large for a solid-state 1,4-addition... 

Cosa G, Chretien MN, Galletero MS, Fornes V, Garcia H, Scaiano JC. Photocatalytic activity of a multicointonent system assembled within zeolites case of 2,4,6-triphenylpyrylium or ruthenium tris(bipyridyl) photosensitizers and titanium dioxide relays within zeolite Y. J Phys Chem B 2002 106 2460-7. 

Imidazole is characterized mainly by the T) (N) coordination mode, where N is the nitrogen atom of the pyridine type. The rare coordination modes are T) - (jt-) realized in the ruthenium complexes, I-ti (C,N)- in organoruthenium and organoosmium chemistry. Imidazolium salts and stable 1,3-disubsti-tuted imidazol-2-ylidenes give a vast group of mono-, bis-, and tris-carbene complexes characterized by stability and prominent catalytic activity. Benzimidazole follows the same trends. Biimidazoles and bibenzimidazoles are ligands as the neutral molecules, mono- and dianions. A variety of the coordination situations is, therefore, broad, but there are practically no deviations from the expected classical trends for the mono-, di-, and polynuclear A -complexes. 

Nagashima reported the hydrogenation of di-, tri- and tetranuclear ruthenium complexes bearing azulenes below 100 °C revealed that only the triruthenium compounds reacted with H2 via triruthenium dihydride intermediates.398 This indicates that there exists a reaction pathway to achieve facile activation of dihydrogen on the face of a triruthenium carbonyl moiety.399... 

We report here results related to the catalytic behaviour of dodecacarbonyl-tri-iron and tri-ruthenium, bis(cyclopentadienyl-dicarbonyliron) and octacarbonyl-di-cobalt deposited on Y-zeolites under F-T conditions. The influence of the nature of the zeolite and of the metal, the dispersion of the metal and the reaction conditions upon activity and products distribution were investigated. 

The ruthenium-catalyzed direct addition of saturated aliphatic alcohols to non-activated alkynes remains a challenge. Only ally alcohol has been successfully involved in the intermolecular addition to phenylacetylene to produce an ether and the enal resulting from Claisen rearrangement (Equation 10.7) [24]. Thus, in refluxing toluene, in the presence of a catalytic amount of RuCl(tris(pyrazolyl) borate) (pyridine)2, a 1 1 mixture of ally P-styryl ether and 2-phenylpent-4-enal was obtained in 72% overall yield. 

The formation of a ruthenium vinylidene is proposed as the key intermediate in the regioselective addition of hydrazine to terminal alkynes [55]. This reaction, which proceeds via addition of the primary amino group of a 1,1-disubstituted hydrazine followed by deamination, provides an unprecedented access to a variety of aromatic and aliphatic nitriles. The tris(pyrazolyl)borate complex RuCl(Tp)(PPh3)2 gave the best catalytic activity in the absence of any chloride abstractor (Scheme 10.17). 

Some years later, at the beginning of the 1970s, first ECL system based on the luminescent transition metal complex tris(2,2 -bipyridine)ruthenium(II)-Ru (bipy)32 + -has been reported.11 It was shown that the excited state 3 Ru(bipy)32 + can be generated in aprotic media by annihilation of the reduced Ru(bipy)31 + and oxidized Ru(bipy)33 + ions. Due to many reasons (such as strong luminescence and ability to undergo reversible one-electron transfer reactions), Ru (bipy)32+ later has become the most thoroughly studied ECL active molecule. 

Polymetallic complexes presenting directional energy migration are of much significance for the design of photochemical molecular devices. Large arrays of multiple photoactive and redox-active building blocks (of ruthenium- or osmium tris(bipyri-dine)-type for instance) have been constructed for such purposes [A. 10,8.25-8.27]. 

There are several methods reported in the literature for transforming vicinal diols into ct-diketones while avoiding the risk of C-C bond cleavage.26 Examples include the standard Swem conditions (dimethyl sulfoxide and oxalyl chloride followed by triethylamine), or the use of DMSO activated by acetic anhydride, pyridine-sulfur trioxide complex, or dicyclohexylcarbodiimide (Mq/J-att oxidation). Diones are also obtained by treatment with benzalacetone as a hydride acceptor in the presence of catalytic amounts of tris(triphenylphosphine)ruthenium dichlonde [(PPh RuCFl.27 Recent developments include the use of w-iodoxyben/.oic acid28 or the oxoammonium salt of 4-acctamidoletramethylpipcridine-1-oxyl and y -toluencNulfonic acid.29... 

Large cations have a powerful effect on neuromuscular transmission, resulting from acetylcholine esterase inhibition and curariform activity. Examples are quaternary nitrogen, phosphorus and arsenic bases and chelate species such as the tris-(2,2 -bipyridine)iron(II) cation when it is injected intravenously. Bis(2,2, 2"-terpyri-dine)ruthenium(Il) perchlorate has about one tenth of the activity of curare182). 

C-H activation pathway cannot be ruled out for this transformation, however. They subsequently observed C-H insertion of a cis substituent by means of isotope studies [32], The cycloheptene product was observed as the major product when cis- or tri-substituted enyne and acetylenic ester termini were present. Ruthenium hydride catalysts reported by Mori and Dixneuf can also initiate the cycloisomerization of 1,5- and 1,6-enynes and dienes [33, 34], The vinylruthenium hydride can be obtained from RuClH(CO)(PPh3)3 or in the presence of acetic acid or ethanol. 

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