Ruthenium complexes carbonyls

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

Ruthenium- and cobalt-catalyzed hydroformylation of internal and terminal alkenes in molten [PBuJBr was reported by Knifton as early as in 1987 [2]. The author described a stabilization of the active ruthenium-carbonyl complex by the ionic medium. An increased catalyst lifetime at low synthesis gas pressures and higher temperatures was observed. 

This system shows an induction period of about six hours before constant activity is attained during which the Ru3(C0)12 undergoes complete conversion to another ruthenium carbonyl complex. In situ nmr studies suggest this species to be the HRu2(C0)e ion. Kinetic studies show complex rate profiles however, a key observation is that the catalysis rate is first order in Pco at low pressures (Pcohigher pressures. A catalysis scheme consistent with these observations is proposed. 

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

Subsequent insertion of CO into the newly formed alkyl-ruthenium moiety, C, to form Ru-acyl, D, is in agreement with our 13C tracer studies (e.g., Table III, eq. 3), while reductive elimination of propionyl iodide from D, accompanied by immediate hydrolysis of the acyl iodide (3,14) to propionic acid product, would complete the catalytic cycle and regenerate the original ruthenium carbonyl complex. 

Although this spectrum does not correspond to any particular ruthenium carbonyl complex, it is consistent with the presence of one or more anionic ruthenium carbonyl complexes, perhaps along with neutral species. Work is in progress with a variable path-length, high pressure infrared cell designed by Prof. A. King, to provide better characterization of species actually present under reaction conditions. 

Reaction at a higher temperature for a longer period leads to formation of the ruthenium carbonyl complex [IR(KBr) 1964 cm 3]. 

I/Ru ratio critical, 34 112 proposed mechanism, 34 112 ruthenium-carbonyl complexes, 34 113 species involved, 34 110-113 -catalyzed homologation, 34 115 proposed mechanism, 34 115 compensation behavior of, 26 285, 286 complex catalyst... 

Finally, the surface-mediated synthesis of ruthenium carbonyl complexes has also been used to prepare supported ruthenium particles. Using silica as a reaction medium and conventional salts, apart from Ru3(CO)i2, mononuclear Ru(CO)j, and high nuclearity carbonyl-derived species can be obtained by CO reductive carbonylation [127, 128]. This opens new routes to preparing tailored supported ruthenium particles. 

Solutions of ruthenium carbonyl complexes in acetic acid solvent under 340 atm of 1 1 H2/CO are stable at temperatures up to about 265°C (166). Reactions at higher temperatures can lead to the precipitation of ruthenium metal and the formation of hydrocarbon products. Bradley has found that soluble ruthenium carbonyl complexes are unstable toward metallization at 271°C under 272 atm of 3 2 H2/CO [109 atm CO partial pressure (165)]. Solutions under these conditions form both methanol and alkanes, products of homogeneous and heterogeneous catalysis, respectively. Reactions followed with time exhibited an increasing rate of alkane formation corresponding to the decreasing concentration of soluble ruthenium and methanol formation rate. Nevertheless, solutions at temperatures as high as 290°C appear to be stable under 1300 atm of 3 2 H2/CO. 

Another possible reason that ethylene glycol is not produced by this system could be that the hydroxymethyl complex of (51) and (52) may undergo preferential reductive elimination to methanol, (52), rather than CO insertion, (51). However, CO insertion appears to take place in the formation of methyl formate, (53), where a similar insertion-reductive elimination branch appears to be involved. Insertion of CO should be much more favorable for the hydroxymethyl complex than for the methoxy complex (67, 83). Further, ruthenium carbonyl complexes are known to hydro-formylate olefins under conditions similar to those used in these CO hydrogenation reactions (183, 184). Based on the studies of equilibrium (46) previously described, a mononuclear catalyst and ruthenium hydride alkyl intermediate analogous to the hydroxymethyl complex of (51) seem probable. In such reactions, hydroformylation is achieved by CO insertion, and olefin hydrogenation is the result of competitive reductive elimination. The results reported for these reactions show that olefin hydroformylation predominates over hydrogenation, indicating that the CO insertion process of (51) should be quite competitive with the reductive elimination reaction of (52). 

The ruthenium carbonyl complexes [Ru(CO)2(OCOCH3)] n, Ru3(CO)12, and a new one, tentatively formulated [HRu-(CO)s ] n, homogeneously catalyze the carbonylation of cyclic secondary amines under mild conditions (1 atm, 75°C) to give exclusively the N-formyl products. The acetate polymer dissolves in amines to give [Ru(CO)2(OCOCH3)(amine)]2 dimers. Kinetic studies on piperidine carbonylation catalyzed by the acetate polymer (in neat amine) and the iiydride polymer (in toluene-amine solutions) indicate that a monomeric tricarbonyl species is involved in the mechanism in each case. 

The results show that a number of ruthenium carbonyl complexes are effective for the catalytic carbonylation of secondary cyclic amines at mild conditions. Exclusive formation of N-formylamines occurs, and no isocyanates or coupling products such as ureas or oxamides have been detected. Noncyclic secondary and primary amines and pyridine (a tertiary amine) are not effectively carbonylated. There appears to be a general increase in the reactivity of the amines with increasing basicity (20) pyrrolidine (pKa at 25°C = 11.27 > piperidine (11.12) > hexa-methyleneimine (11.07) > morpholine (8.39). Brackman (13) has stressed the importance of high basicity and the stereochemistry of the amines showing high reactivity in copper-catalyzed systems. The latter factor manifests itself in the reluctance of the amines to occupy more than two coordination sites on the cupric ion. In some of the hydridocar-bonyl systems, low activity must also result in part from the low catalyst solubility (Table I). 

Reaction at a higher temperature for a longer period leads to formation of the ruthenium carbonyl complex [IR(KBr) 1964 cnv ], This undesired reaction is suppressed under the present conditions. Use of commercial [RuCl2(1,5-cyclooctadiene)]n or readily available RuCl2[Sb(CaHs)3]33 gives similar results on heating in DMF at 160°C for 20 min or in o-dichlorobenzene at 160°C for 10 min. N.N-Dimethylacetamide can be used in place of DMF. 

Ruthenium carbonyl complexes have been shown to catalyze a number of car-bonylation processes. The ruthenium-catalyzed intramolecular Pauson-Khand reaction was found to proceed in the presence of Ru3(CO)12 (Eq. 105) [165,166]. The reaction is a valuable tool for selective organic synthesis. 

Ruthenium carbonyl complexes, for example, Ru3(CO) 12 can be used as catalysts for the synthesis of oligosilazanes via dehydrocoupling of Si-H bonds with H-N bonds (Eq. 117) [185]. 

Treatment of the disubstituted vinylidene complex 124 with base in wet methanol cleaves the vinylidene bond to give the cationic ruthenium carbonyl complex 126 and bibenzyl in good yield. This reaction presumably proceeds via initial formation of the acyl complex 125, which decomposes to give the products [Eq. (106)] (78). Other mono- and disubstituted vinylidene complexes, however, do not give identifiable decomplexation... 

Experiments with cyclooctatetraene and its methyl and phenyl derivatives have demonstrated that reaction with certain ruthenium carbonyl complexes can occur with transannular bonding to give pentalene complexes directly.253,264 The structures of these unique molecules have been confirmed by X-ray crystallography. 

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),... 

Recent literature describes the synthesis of vinyl esters in the presence of platinum metal complexes. Complexes which have proven particularly suitable in this context are those of ruthenium (eq. (15)), such as, for example, cyclooc-tadienylruthenium halides [36], ruthenium carbonyl complexes, and ruthenium acetate complexes [37]. A characteristic feature of these is their high selectivity with regard to acetylene, so that the production of acetylene polymers is reduced. 

Watanabe et al. reported that the addition of C-H bonds in aldehydes to olefins took place efficiently with the aid of Ru3(CO)12 under a CO atmosphere at 200°C (Eq. 51) [118]. They also reported that the same ruthenium-carbonyl complex catalyzes the addition of the C-H bonds in formic acid esters and amides to olefins (Eq. 52) [119]. 

Ruthenium carbonyl complex undergoes successive oxidative addition of Si-Si bond of 1 to give tetrakis(organosilyl)(CO)3Ru(IV) complex 30 as a major,kinetic product, which further reacts with the Ru3(CO)12 to give bis(silyl)Ru(II) complex 31 (Eq. 13) [28],... 

A very prominent class of metalloporphyrins are the tetra(aryl)porphyrin ruthenium carbonyl complexes [(Aryl)4Por)Ru(CO)(L)] (L = solvent) that, in... 

In this section, we will review the nature and chemical reactivities of several kinds of ruthenium complexes under the following headings ruthenium carbonyl complexes, dichlororuthenium complexes, chlorohydrido complexes, dihydridoruthenium complexes, ruthenium complexes with chiral ligands, ruthenium complexes with cyclopentadienyl ligands, and ruthenium arene/diene complexes. 

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