Triosmium dodecacarbonyl,

Clusters Ru3(CO)l2 and Os3(CO)l2 as well as their substitution products, e.g. [Os3(CO)lo(AN)2], activate pyrrole and its derivatives in many different ways. Thus, dihydrides 43 (R = H, Me) follow from triosmium dodecacarbonyl and pyrrole or 1-methylpyrrole [82JCS(D)2563 84P1175 86JOM(311)371]. Complex 43 (R = H) isomerizes as a result of proton transfer to the more stable species 44 and... 

Reaction of acetylenic complexes with triosmium dodecacarbonyl leads to a variety of products involving one, two, or three acetylenic units. As with ruthenium, for the monosubstituted alkynes, hydrogen transfer can occur to the metal cluster. Thus, Os3(CO)12 and phenyl-acetylene (L) yield, in refluxing benzene, the derivatives Os3(CO)10L, Os3(CO)10L2, Os3(CO)9L, and HOs3(CO)9(L-H). The general chemistry is summarized in Scheme 2 (131). 

Triosmium dodecacarbonyl reacts with the simple ligand vp in an atypical manner 37) the trimeric osmium nucleus is retained and the olefin attacked to give a complex of formula Os3(CO)8(vp), which has two hydrides attached to osmium atoms. These are possibly a and one / -hydrogen of the olefin, the remainder being r-bonded to the trimeric osmium core. 

The reaction is run in a 250-mL flat-bottomed three-necked flask containing a magnetic stirrer and equipped with a gas inlet tube and a reflux condenser connected to a mercury check-valve to ventilate evolved gases. Octane is dried over sodium and freshly distilled before use. Triosmium-dodecacarbonyl and cyclopentadienylnickelcarbonyl dimer are commercially available (Strem). Alternatively, Os3(CO)12 may be synthesized from commercially available materials by a tested procedure.1... 

Bridges between trinuclear metal clusters [of Ru, Os] Synthesis of ruthenium and osmium carbonyl clusters with unsaturated organic rings Oxyligand derivatives of triosmium dodecacarbonyl... 

Triosmium dodecacarbonyl (Os 3(00)12)/ yellow crystalline solid/ was first prepared by decon osition of the Os(CO)5 obtained by carbonylation of osmiton tetrox-ide at elevated temperatures and pressures (196). Initially Os 3(CO)12 was incorrectly identified as 0s2(C0)g, in an error analogous to that associated with the identification of Ru3(C0)i2 discussed previously. In this case this error was corrected not only by a crystal structure of 033(00)12 by x-ray diffraction (87, 88) but also by the recent (304) preparation of authentic Os2(CO)g as a yellow, thermally unstable ( 75 C) solid by the photolysis of Os(CO)5 at -40°C. The x-ray-diffraction study of 033(00)12 demonstrated structure 11 (M = Os) with no bridging... 

We discovered [10] that triosmium dodecacarbonyl (compound 1.3, Fig. 1.7) catalyzes a very efficient oxidation of alkanes by H2O2 in MeCN to afford alkyl hydroperoxides (primary products) as well as alcohols and ketones (aldehydes) at 60 °C if pyridine is added in a low concentration. TONs attained 60,000 (Fig. 1.8a) and turnover frequencies were up to 24, 000 h A plateau in the dependence of on initial concentration of cyclooctane, [RH] (Fig. 1.8b), indicates that there is a competition between RH and another component of the reaction mixture for a transient oxidizing species. Indeed, at high concentration of the hydrocarbon, all oxidizing species are accepted by RH and the maximum possible oxidation rate is attained. This concurrence can be described by the following kinetic scheme ... 

Earlier some of us discovered [8] an extremely powerful oxidizing system composed of triosmium dodecacarbonyl (19.1) and hydrogen peroxide, which was very efficient for the oxidation of alkanes to alkyl hydroperoxides in acetonitrile solution at 60 °C. The addition of pyridine in low concentration sufficiently improves the activity. Turnover number (TON) and turnover frequency (TOE) attained 60,000 and 24,000 h , respectively. Although the system operates with the formation of free radicals, the product selectivity in the alkane oxidation under certain conditions was very high because an alkyl hydroperoxide is formed as the sole product. We applied this system to the oxidation of alcohols, including easily oxidizable 1-phenylethanol and glycerol. The kinetic curves of the alcohol consumption and ketone accumulation shown in Fig. 19.1 indicate that the ketone is formed in the yield circa 25%. 

The substitution of triosmium dodecacarbonyl by arsine and phosphine derivatives under mild conditions yields a series of simple substitution products. 

Os3(GO)ii(NGMe) reacts with thiols, forming (/x-H)Os3(GO)io(/x-SR) clusters through the intermediacy of Os3(GO)ii(HSR) complexes where the thiol is bound to one osmium atom through the S-H bond. " Thioureas also react with triosmium dodecacarbonyl ... 

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