Metal—carbon bonding preparation

The preparation of semiconductors by thermal decomposition would appear to be impossible because of the high amount of energy required to break all of the metal-carbon bonds before the atomic species could be formed. However, the thermal method is successful because the reaction to form free methyl radicals, which combine to form ethane, lowers the energetic requirements for the formahon of gallium, for example, according to the equation... 

Like graphite, C60 can be transformed into diamond, but the process requires less stringent conditions. It has also been found that Cso becomes a superconductor at low temperature. Another interesting characteristic of Cso is that when it is prepared in the presence of certain metals, the Cso cage can enclose a metal atom. In some cases, other materials can be enclosed within the C60 cage in a "shrink wrapped" manner to form "complexes" that are described as endohedral. It has also been possible to prepare metal complexes of Cso that contain metal-carbon bonds. A compound of this type is (C6H5P)2PtC60. 

The free dithiocarboxylic acids can be isolated, but their salts are preferred. In some cases their metal complexes can be prepared directly by insertion of carbon disulfide into metal-carbon bonds. Thus, the reaction of Grignard reagents, RMgX, with CS2, followed by acid treatment gives the dithiocarboxylic acids RCSSH and metal complexes in good yields.311... 

A further method for preparing acyl complexes consists in the treatment of alkyl complexes containing at least one carbonyl ligand with a strong ligand [44,105,106], Thereby 1,1-insertion of the carbonyl group into the metal-carbon bond can... 

In 1977, an article from the authors laboratories [9] reported an TiCV mediated coupling reaction of 1-alkoxy-l-siloxy-cyclopropane with aldehydes (Scheme 1), in which the intermediate formation of a titanium homoenolate (path b) was postulated instead of a then-more-likely Friedel-Crafts-like mechanism (path a). This finding some years later led to the isolation of the first stable metal homoenolate [10] that exhibits considerable nucleophilic reactivity toward (external) electrophiles. Although the metal-carbon bond in this titanium complex is essentially covalent, such titanium species underwent ready nucleophilic addition onto carbonyl compounds to give 4-hydroxy esters in good yield. Since then a number of characterizable metal homoenolates have been prepared from siloxycyclopropanes [11], The repertoire of metal homoenolate reactions now covers most of the standard reaction types ranging from simple... 

A recipe for the preparation of Prussian Blue was published 20 years after its discovery.10 " Since materials containing iron, potash and nitrogenous matter such as blood or animal hooves may have been heated together in more remote times, ferrocyanides [hexacyanoferrates(II)] probably antedate Diesbach s discovery. They contain Fe—CN bonds and may thus possibly be considered as the first known examples of coordination compounds containing transition metal—carbon bonds (organometallic compounds). 

At present there are few examples of isolable, well-characterized sources of tellurolate anions (RTe-).1 Although insertion of elemental tellurium into reactive metal-carbon bonds has been known for many years, the resulting solutions contain a mixture of compounds in addition to the RTe- species of interest.2 Alkali metal phenyltellurolate salts, prepared via metal reduction of diphenyl ditelluride in liquid ammonia, were first isolated by Klar and co-workers.3 More recently Lange and Du Mont reported the synthesis of the bulky aryl tellurolate (THF)3Li[Te(2,4,6-f-Bu3C6H2)],4 and Sladky described the in situ formation of a bulky alkyl tellurolate via reaction of tellurium with LiC(SiMe3)3.5 Acidification of aryltellurolate anions affords thermally sensitive tellurols (RTeH) that are stable only below room temperature.6... 

The other carbon dioxide complex characterized by x-ray crystallography contains two linked C02 molecules in the coordination sphere (116). This complex, [IrCl(C204)(PMe3)3], was prepared by the interaction of C02 with chloro(cyclooctene)[tris(trimethylphosphine)]iridium(I), [IrCl(C8 H j 4)-(PMe3)3], in benzene solution. The structure, (25), shows essentially octahedral coordination about the iridium center, with one metal-carbon bond and a five-membered chelate ring formed with the second C02 molecule. 

Products of the carbometallation 442 and 443 contain very reactive metal carbon bonds, and can not be isolated in many cases. They undergo further reactions such as protonation, transmetallation and nucleophlic attack. The preparation of tri- or tetrasubstituted alkenes 444 and 445 from alkynes via the alkenylmetals 443 is particularly useful. Only catalysed carbometallations are treated here. 

These processes were extended to preparation procedures and application to the organic synthesis of organome-tallic tetrazole derivatives, including 5-metallated tetrazoles and tetrazoles with a metal-carbon bond in a substituent, and also of organotin tetrazoles <2005RJ01565>. 

A (triphenylene)Cr(CO)3 complex and its crystal structure212 has been described in which the Cr—C distance of this -complex is around 2.2 A, common for transition-metal-carbon bond distances. A redox-tunable near-IR dye based on a trinuclear ruthenium-(II) complex of hexahydroxytriphenylene 87 has been prepared.220 Here, the absorption maximum of the... 

Most coordination catalysts have been reported to be formed in binary or ternary component systems consisting of an alkylmetal compound and a protic compound. Catalysts formed in such systems contain associated multinuclear species with a metal (Mt)-heteroatom (X) active bond ( >Mt X Mt—X > or — Mt—X—Mt—X— Mt = Al, Zn, Cd and X = 0, S, N most frequently) or non-associated mononuclear species with an Mt X active bond (Mt = Al, Zn and X = C1, O, S most frequently). Metal alkyls, such as triethylaluminium, diethylzinc and diethylcadmium, without pretreatment with protic compounds, have also been reported as coordination polymerisation catalysts. In such a case, the metal heteroatom bond active in the propagation step is formed by the reaction of the metal-carbon bond with the coordinating monomer. Some coordination catalysts, such as those with metal alkoxide or phenoxide moieties, can be prepared in other ways, without using metal alkyls. There are also catalysts consisting of a metal alkoxide or related compound and a Lewis acid [1]. 

Complexes of the type [Rh(TPP)(RX)] [RX = C H X (n = 3-5, X = Cl or Br n = 3-6, X = I) TPP = dianion of tetraphenylporphyrin] were prepared by Anderson et al. (179). The nature of RX was found to determine the overall electrochemical behavior for the reduction of [Rh(TTP)(RX)]. For some complexes, specifically those where X = Br and I, the bound alkyl halide could be reduced without cleavage of the metal-carbon bond. This resulted in the electrochemically initiated conversion of [Rh(TPP)(RX)] to a [Rh(TPP)(R)] complex. The E. value for this reduction was dependent on the chain length and halide of the RX group and followed the trend predicted for alkyl halides. The reduction of the bound RX occured at Ei values significantly less negative that those for reduction of free RX under the same solution conditions. 

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