Ruthenium complexes mononuclear compounds

Quite recently, some mononuclear ruthenium complexes such as [(p-cymene)RuX-(CO)(PR3)]OTf (X = Cl, OTf, R = Ph, Cy) have been found to work as catalysts for the propargylation of aromatic compounds such as furans, where some ruthenium complexes were isolated as catalytically active species from the stoichiometric reactions of propargylic alcohols (Scheme 7.27) [31]. The produced active species promoted the propargylation of furans vdth propargylic alcohols bearing not only a terminal alkyne moiety but also an internal alkyne moiety, indicating that this propargylation does not proceed via allenylidene complexes as key intermediates. 

Organometallic Compounds. Ruthenium, predominately in the oxidation states 0 and +2, forms numerous mononuclear and polynuclear organometalhc compounds. A few examples of compounds in both higher and lower oxidation states also exist. The chemistry of polynuclear ruthenium complexes is extensive and has been reviewed (53—59). 

Binuclear [RuX2(arene)]2 (1) and mononuclear RuX2(L) (arene) (3) derivatives have been shown to be useful precursors for access to alkyl-or hydrido(arene)ruthenium complexes. The latter are key compounds for the formation of arene ruthenium(O) intermediates capable of C—H bond activation leading to new hydrido and cyclometallated ruthenium arene derivatives. Arene ruthenium carboxylates appear to be useful derivatives of alkyl-ruthenium as precursors of hydrido-ruthenium complexes their access is examined first. 

Although ruthenium is significantly less expensive than rhodium and although its use has been recommended since 1960 (7) for the oxo synthesis, complexes of this metal have not been developed as catalysts. However, many papers and patents have referred to the results obtained employing various ruthenium complexes. The purpose of this article is to analyze the work done involving ruthenium compounds, restricting the scope only to the hydroformylation reaction and not to the carbonylation reaction, which would demand to too lengthy an article. In this review we examine successively mononuclear ruthenium complexes, ruthenium clusters as precursors, photochemical activation, and supported catalysis. 

Reactions between salts of [m Jo-7-CBioHi3] and [Fc3(CO)i2] afford the mononuclear anionic iron compound [2,2,2-(CO)3-c/o5o-2,l-FeCBioHn], typically isolated as its [N(PPh3)2] salt (11) (Chart 4). No anionic triiron complex analogous to 5 and 7 is formed in this reaction. The anionic mononuclear iron, ruthenium and osmium complexes and the previously mentioned neutral mononuclear ruthenium dicarbollide complex 4, obtained from [Ru3(CO)i2] and /Jo-7,8-C2BgHi3, are iso-lobal with the cyclopentadienide species [Mn(CO)3(ri-C5H5)] and [Fe(CO)3 (il-CsHs)]. ... 

Ruthenium(iv).—Several novel Ru compounds have been isolated from the reaction sequence shown in Scheme 9. These diamagnetic complexes are assumed to be mononuclear with two trans oxide groups. In addition, the dinuclear complex [Ru(0H)3(phen)]20 was reported to be formed by evaporating a methanolic solution of [Ru03(phen)]20. A study of the mechanism... 

Mononuclear ruthenium compounds acyl complexes, 6, 398 agostic complexes, 6, 392 alkenyl complexes... 

Mono- and Dinuclear Compounds. The pentacarbonyl is a starting material for mononuclear ruthenium carbonyl complexes. As outlined in Scheme 3, reduction with sodium in liquid ammonia yields a pale-colored anion solution (5),... 

The formation of allenylidene derivatives from ethynyl-hexanol and alkenyl-vinylidene mononuclear complexes (9), the formation of mononuclear ruthenium allenyl complexes from terminal alkynes (10), the intermediacy of ruthenium-allenylidene complexes in forming propargylic alcohols (II), and in the cyclization of propargyl alcohols (12), and the use of mononuclear ruthenium compounds in allylic alkylation catalysis (13) have also been reported. 

The diruthenium(O) complexes [Ru2(CO) J,-(RO)2PN(Et)P(OR)2 2] (3, R = Me, Pr) (Scheme 2) have been reported to react with dihydrogen affording l,2-dihydrides.[13] Despite the formal similarity between these compounds and the previously described iridium and rhodium dppm derivatives, they display different coordination environments around the metal atoms. This could be related to the fact that, unlike the typical planar structure of most mononuclear d species, the unsaturated zerovalent ruthenium fragments adopt a structure which resembles a trigonal bipyramid with an empty equatorial site. [14]... 

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