Methylene, osmium complex

Methanol, platinum complex, 26 135 tungsten complex, 26 45 Methyl, iridium complex, 26 118 manganese complex, 26 156 osmium complex, 27 206 rhenium complexes, 26 107 Methyl acetate, iron complex, 27 184 osmium complex, 27 204 Methyl benzoate, chromium complex, 26 32 Methylene, osmium complex, 27 206 Molybdate(l -), (acetato)pentacarbonyl-, M.-nitrido-bis(triphenylphosphorus) (I-h), 27 297... 

CHF,0,S, Methanesulfonic acid, trifluoro-, iridium, manganese, and rhenium complexes, 26 114, 115, 120 platinum complex, 26 126 CHOSj, Dithiocarbonic acid, 27 287 CH, Methylene, osmium complex, 27 206 CHiOj, Formic acid, rhenium complex, 26 112... 

CH2, Methylene, osmium complex, 27 206 CHjBr, Methane, bromo-, osmium and mthenium complexes, 27 201,205 CHjCl, Methane, chloro-, osmium complex, 27 205... 

While the tantalum methylene complex 2 reacts with Mel (15), the osmium complex 3 is quite unreactive, suggesting greater nucleo-philicity of the former compound. 

Terminal methylene complexes are relatively rare—less than 10 such compounds have been isolated and about as many again have been characterized by spectroscopic techniques only. The methylene complexes previously reported fall into two groups, (i) neutral complexes of the early transition metals (e.g., Ti, Ta) and (ii) cationic complexes of the later transition metals (e.g., Re, Fe). The osmium complex 47 is important, then, as it is a new example extending the neutral group to the later transition metals. Compound 47 is the prototype for the series Os(=CHR)Cl(NO)(PPh3)2 and is one of only three terminal methylene complexes to be structurally characterized by X-ray crystallography (see Section IV,B). 

Scheme 8.17 Preparation of the methylene osmium(O) complex 64 and its reactions with S8, CO, S02 and [Aul2] (as precursor of Aul) to form the 1 1 adducts 65-68...

The reaction of tellurium with osmium-carbyne complexes or with osmium-methylene complexes, or of sodium hydrogen telluride with iodomethyl(iodo)-osmium complexes produced tellurolato-osmium compounds. 

CF3H, Methane, trifluoro-cadmium complex, 24 55 mercury complex, 24 52 CF3NOS, Imidosulfurous difluoride, (fluorocarbonyl)-, 24 10 CH2, Methylene ruthenium complex, 25 182 CH2CI4P2, Phosphine, methylenebis-(dichloro)-, 25 121 CH3, Methyl cobalt complexes, 23 170 mercury complexes, 24 143-145 platinum complex, 25 104, lOS CNO, Cyanato silicon complex, 24 99 CN2OS2, l,3k, 2,4-Dithiadiazol-5-one, 25 53 CO, Carbon monoxide chromium complexes, 21 1, 2 23 87 cobalt complex, 25 177 cobalt, iron, osmium, and ruthenium complexes, 21 58-65 cobalt-osmium complexes 25 195-197 cobalt-ruthenium cluster complexes, 25 164... 

A noted earlier, coordination of transition-metal ions to water-soluble polymers can allow for facile catalyst recovery, by ultrafiltration, from water-soluble substrates and/or products. For example, Han and Janda [22] used an osmium complex of the water-soluble polymeric chiral ligand 8 as a catalyst for the asymmetric dihydroxylation of alkenes in aqueous acetone (Eq. 5). However, they suggested that the catalyst should be recovered by precipitation with methylene chloride. Obviously the use of an ultrafiltration membrane for catalyst separation would be far more attractive. nu... 

Remarkably, both alkyl and aryl C-H activations have been described in the formation of the metallacyclic osmium(iv)-hydride complex 25, generated as the minor component (12%) of a mixture with the deprotonated methylene-amido complex [Os(=N=CH2)Gp(GH2SiMe3)2], from the reaction of the imido complex [Os(=NMe)Cp(CH2SiMe3)2][OTf] with PPhs. ... 

Gauvin, R. M. Rozenberg, H. Shimon, L. J. W. Ben-David, Y. Milstein, D. Osmium-mediated C—H and C—C bond cleavage of a phenolic substrate p-quinone methide and methylene arenium pincer complexes. Chem. Eur. J. 2007, 13, 1382-1393. 

The tantalum center in the Schrock methylene complex 2 is electron rich by virtue of the electron-releasing ligands coordinated to it, while the osmium and ruthenium center in the methylene 3 and difluorocarbene 4 species are electron-rich because they have d8 electron configurations in neutral complexes. 

The intermediacy of cationic d6 osmium methylene complex 6 is implicated in the reactions of OsI(CH2I)(CO)2(PPh3)2 with nucleophiles (23), e.g.,... 

The effect of metal basicity on the mode of reactivity of the metal-carbon bond in carbene complexes toward electrophilic and nucleophilic reagents was emphasized in Section II above. Reactivity studies of alkylidene ligands in d8 and d6 Ru, Os, and Ir complexes reinforce the notion that electrophilic additions to electron-rich compounds and nucleophilic additions to electron-deficient compounds are the expected patterns. Notable exceptions include addition of CO and CNR to the osmium methylene complex 47. These latter reactions can be interpreted in terms of non-innocent participation of the nitrosyl ligand. 

The characteristic reactivity of neutral dg alkylidene complexes of Ru, Os, and Ir is with electrophilic reagents. The osmium methylene 47 reacts with the widest range of electrophiles, the most significant reactions being summarized in Scheme 2. 

The ruthenium and iridium methylene complexes and the osmium alkylidenes 48-50 also react with S02 to afford sulfene complexes (104). 

Thus methyl and chalcoformaldehyde complexes of osmium are accessible by both electrophilic addition to a neutral d8 methylene complex and nucleophilic addition to a cationic d6 methylene complex. 

The first osmium(IV) thiolato complex, [Os(salen)(SPh)2] (132), was prepared by the reduction of [0s(0)2(salen)] with thiophenol in CH2Cl2. The complex has a distorted octahedral structure, and both phenyl groups tilt away from the methylene bridge of the salen ligand, which is in the gauche confirmation. The mean Os—S distance is 2.32 A, which is shorter than that (2.415 A) in [Os2(Et2dtc)6](PF6)2 (Et2dtc = A,A-diethyldithiocarbamate). 

It should also be noted that hydrocarbon activation is a possible alternative entry to methylene polymerization methane, for example, may activate at metal sites to yield surface-methyl species adjacent to each other (eq. (12)). There is a molecular precedent of binuclear, intramolecular methane elimination from such structures (osmium) to yield -methylene complexes [31]. 

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