Triosmium

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... 

Reactions of triosmium clusters with organic compounds. K. Burgess, Polyhedron, 1984. 3, 1175... 

An early example of surface-mediated synthesis led to the conversion of Os3(CO)i2 into [Os5C(CO)i4] [13]. Quantitative characterization of the formation of this cluster on MgO by C NMR spectroscopy [15] showed that the synthesis gave [OssCCCOIh] " in a yield of about 65% other products included triosmium and tetraosmiimi carbonyl clusters. A schematic representation of the surface chemistry is shown in Fig. 1. 

Examples of O-alkylation have also been demonstrated for triruthenium and triosmium anionic clusters, as well as the tetrairon cluster Fe CO)] - (31-33). This reaction has considerable promise as an entry into many different methylidyne complexes through the replacement of the OR" group, eq. 20 (38). 

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). 

The complexes appear to be based on a tetrahedral distribution of metal atoms, with the di- and triosmium derivatives containing no bridging carbonyl group. A detailed X-ray structure of the complex H3CoOs3(CO)12 has been carried out (249). 

Scheme 61. Synthesis of the silsesquioxane triosmium cluster compound 180.

Recently, the oxidative addition of C2-S bond to Pd has been described. Methyl levamisolium triflate reacts with [Pd(dba)2] to give the cationic palladium complex 35 bearing a chiral bidentate imidazolidin-2-ylidene ligand [120]. The oxidative addition of the levamisolium cation to triruthenium or triosmium carbonyl compounds proceeds also readily to yield the carbene complexes [121], The oxidative addition of imidazolium salts is not limited to or d transition metals but has also been observed in main group chemistry. The reaction of a 1,3-dimesitylimidazolium salt with an anionic gallium(I) heterocycle proceeds under formation of the gaUium(III) hydrido complex 36 (Fig. 12) [122]. 

Spectroscopic evidence (IR, Raman, NMR and EXFAS) [155] shows that the triosmium carbonyl clusters Os3(CO)i2 and Os3(CO)io( i-H) react with a silica surface to yield the monosiloxy species [( x-=SiO)((x-H)Os3(CO)io]. The monosiloxy molecular analogue [((x-OSiEt3)Os3( t-H)(CO)io] has been obtained from Et3SiOH [156]. Disilanols Ph2Si(OH)2 and (OH)Ph2SiOSiPh2(OH) lead to the same triosmium monosiloxy motif, [( t-0)Os3( t-H)(CO)io] [157], and the thermal and chemical... 

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. 

Aime S, Diana E, Gobetto R, Milanesio M, Vails E, Viterbo D (2002) Structural and spectroscopic study of the dihydrogen bond in an imine triosmium complex. Organometallics 21 50-57... 

A 500-mL two-necked round-bottomed Pyrex flask is fitted with a gas dispersion tube and a reflux condenser connected to a bubbler. The flask is charged with 0.191 g (0.20mmol) of (/z-benzenethiolato)-decarbonyl- -hydrido-triosmium and 250 mL of cyclohexane. The solution is purged with carbon monoxide (flow rate 50 mL min 1) for 15 min. Then the flow rate is increased to 100 mL min -1 and the solution is irradiated for 2.0 to 2.5 h by using an external high-pressure mercury lamp (e.g., Philips HPK 125 W). The lamp should be maintained at least 12 in. from the reaction flask to minimize heating of the solution. Heating decreases the yield of 2. 

Such a reaction occurs because the Os=Os double bond of Os3(/t-H)2(CO)10 is well known to be reduced upon addition of a variety of nucleophiles including those that are metal centered.3 This di-fi-hydrido triosmium... 

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