Ruthenium carbonyl halides

Ruthenium, Os, Rh, Ir, Pd and Pt carbonyls, including hydrido, halogeno and mixed-ligand carbonyls, have been reviewed . Reviews also have appeared on ruthenium carbonyl halides and on carbonyl derivatives of Ti, Zr and Hf . 

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)... 

A particularly interesting case is that of the platinum metal group which, in addition to platinum (Pt), comprises ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), and palladium (Pd). These carbonyl halides are usually the most practical precursors for metal deposition because of their high volatility at low temperature. Indeed two of them, palladium and platinum, do not form carbonyls but only carbonyl halides. So does gold. 

The picture is different for the bimetallic ruthenium-rhodium systems both metals in the presence of iodide promoters and CO give anionic iodocarbonyl species, namely [Ru(C0) I ] and [Rh(CO)2l2] j but the range of I, CO concentration and temperature in which the anions exist and are catalytically active in carbonylation reactions is different. [Ru(CO)3l2] species in fact are extensively transformed at high temperature and low carbon monoxide pressure by an excess of I (i.e. I/Ru 50) into catalytically inactive [Ru(CO)2l4] (v q 2047, 1990 cm"l in THF (JJ.)) (eq. 1), whereas [Rh(CO)2l2] can work in the carbonylation process only in the presence of a large excess of I"" (I/Rh 100-1000) which prevents reduction to metal (12) (for instance at 150 C rhodium(I) carbonyl halides, [Rh(CO) X2]"", without CH3I under a CO/H2 pressure of 10 MPa are completely reduced to metal). 

What is especially intriguing is the reverse behavior exhibited by the use of ruthenium carbonyl as the metal carbonyl. This reaction, which is catalytic in both Ru3(CO)2 and quaternary ammonium halide (which accelerates the rate of formation of the hydride intermediate), occurs in much higher yield under a carbon monoxide than a nitrogen atmosphere (22). The reaction conditions used for the Ru3(CO)12-catalyzed reaction are much milder than those reported using the water gas shift reaction [100°C, 500 psi] (25). 

This section covers the chemistry of pure halides, aqua-, hydroxo-, oxo- and carbonyl halides. For nitrido and nitrosyl halides see Sections 45.4.6 and 45.4.4.4 respectively. Unlike most other sections of this article, much of the published work on ruthenium halides is pre-1970 and excellent, detailed reviews2,3 have appeared in the literature. Therefore in order to conserve space and avoid undue repetition, only a relatively brief account containing earlier key references and more recent data is presented here. 

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. 

Homogeneous hydrogenation of carbon dioxide to methanol is catalyzed by ruthenium cluster anions in the presence of halide anions. The catalyst system was Ru3(CO)i2 and alkyl iodides in A -methylpyrrolidone (NMP) solution at 513 K. Some methane was also formed. FT-IR spectra of the reactions allowed identification of several ruthenium carbonyl anions. 

Ruthenium II) carbonyl anrf carbonyl halide complexes... 

Preliminary results of the reaction between vanadium(iii)-tetrasulpho-phthalocyanine complex with oxygen have been reported these data were compared with those obtained for the corresponding reaction of the hexa-aquo complex ion. The oxidation of methyl ethyl ketone by oxygen in the presence of Mn"-phenanthroline complexes has been studied Mn " complexes were detected as intermediates in the reaction and the enolic form of the ketone hydroperoxide decomposed in a free-radical mechanism. In the oxidation of 1,3,5-trimethylcyclohexane, transition-metal [Cu", Co", Ni", and Fe"] laurates act as catalysts and whereas in the absence of these complexes there is pronounced hydroperoxide formation, this falls to a low stationary concentration in the presence of these species, the assumption being made that a metal-hydroperoxide complex is the initiator in the radical reaction. In the case of nickel, the presence of such hydroperoxides is considered to stabilise the Ni"02 complex. Ruthenium(i) chloride complexes in dimethylacetamide are active hydrogenation catalysts for olefinic substrates but in the presence of oxygen, the metal ion is oxidised to ruthenium(m), the reaction proceeding stoicheiometrically. Rhodium(i) carbonyl halides have also been shown to catalyse the oxidation of carbon monoxide to carbon dioxide under acidic conditions ... 

The following metal compounds are used for the preparation of the catalysts oxides, metal carbonyls, halides, alkyl and allyl complexes, as well as molybdenum, tungsten, and rhenium sulfides. Oxides of iridium, osmium, ruthenium, rhodium, niobium, tantalum, lanthanum, tellurium, and tin are effective promoters, although their catalytic activity is considerably lower. Oxides of aluminum, silicon, titanium, manganese, zirconium as well as silicates and phosphates of these elements are utilized as supports. Also, mixtures of oxides are used. The best supports are those of alumina oxide and silica. 

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