Mechanism organometallic compound

Landis C R, D M Root and T Cleveland 1995. Molecular Mechanics Force Fields for Modeling Inorgani and Organometallic Compounds. In Lipkowitz K B and D B Boyd (Editors). Reviews in Compute tional Chemistry Volume 6. New York, VCH Publishers, pp. 73-148. 

The introduction of additional alkyl groups mostly involves the formation of a bond between a carbanion and a carbon attached to a suitable leaving group. S,.,2-reactions prevail, although radical mechanisms are also possible, especially if organometallic compounds are involved. Since many carbanions and radicals are easily oxidized by oxygen, working under inert gas is advised, until it has been shown for each specific reaction that air has no harmful effect on yields. 

The bimetallic mechanism is illustrated in Fig. 7.13b the bimetallic active center is the distinguishing feature of this mechanism. The precise distribution of halides and alkyls is not spelled out because of the exchanges described by reaction (7.Q). An alkyl bridge is assumed based on observations of other organometallic compounds. The pi coordination of the olefin with the titanium is followed by insertion of the monomer into the bridge to propagate the reaction. 

Today the term anionic polymerisation is used to embrace a variety of mechanisms initiated by anionic catalysts and it is now common to use it for all polymerisations initiated by organometallic compounds (other than those that also involve transition metal compounds). Anionic polymerisation does not necessarily imply the presence of a free anion on the growing polymer chain. 

Reutov, O. A., The mechanisms of the substitution reactions of non-transition metal organometallic compounds, J. Organomet. Chem. 100, 219 (1975). 

It might be mentioned that matters are much simpler for organometallic compounds with less-polar bonds. Thus Et2Hg and EtHgCl are both definite compounds, the former is a liquid and the latter is a solid. Organocalcium reagents are also known, and they are formed from alkyl halides via a single electron transfer (SET) mechanism with free-radical intermediates. "... 

It seems likely that the mechanism of the Wurtz reaction consists of two basic steps. The first is halogen-metal exchange to give an organometallic compound (RX -(- M —+ RM), which in many cases can be isolated (12-36). Following this, the organometallic compound reacts with a second molecule of alkyl halide (RX + RM —> RR). This reaction and its mechanism are considered in the next section (10-94). 

It is unlikely that a single mechanism suffices to cover all conversions of organometallic compounds to alkyl halides. In a number of cases the reaction has been shown to involve inversion of configuration (see p. 762), indicating an Se2 (back) mechanism, while in other cases retention of configuration has been shown, implicating an Se2 (front) or SeI mechanism. In still other cases, complete loss of configuration as well as other evidence have demonstrated the presence of a free-radical mechanism. ... 

Reutov, O. A., and Beletskaya, I. P., Reaction Mechanisms of Organometallic Compounds, pp. 215-219. North-Holland Publ., Amsterdam, 1968. 

Organometallic Nitrogen Compounds of Germanium, Tin, and Lead, 3, 397 Organometallic Pseudohalides, S, 169 Organometallic Reaction Mechanisms, 4, 267 Organopolysilanes, 6, 19... 

In this review we shall not deal with the synthesis of this coordination complex, but we shall deal with the chemical properties of B 12-coenzymes with special emphasis on how these properties relate to Bi2-enzyme mechanisms. Also, we shall show how B -catalyzed methyl-transfer reactions have special significance in the biosynthesis of methylated heavy metals in the aqueous environment, and how the synthesis of these organometallic compounds has special relevance to problems concerned with continuing global environmental health hazards. 

The mechanisms of thermally initiated decarboxylations giving organometallic compounds have generally not been studied in detail, and mechanistic conclusions have largely been derived from substituent or... 

The vanadium-promoted epoxidation method has proved to be valuable in synthetic routes leading to dl-Ci8 Cecropia juvenile hormone20 and lasalocid A.24 The mechanism of vanadium-mediated epoxidation has been elucidated25 but an evaluation of the use of other organometallic compounds as epoxidation reagents is required.26... 

One of the several mechanisms for decarboxylation is the reverse of the familiar carboxylation reaction of organometallic compounds or carbanions. Many of the acids RCOOH that are readily decarboxylated in basic media are compounds for which the corresponding R( ) is a comparatively stable carbanion.405 The postulated intermediate has actually been trapped or diverted in a few cases as the product of an aldol condensation.406... 

The removal of an electron from a carbanion oxidizes it to a free radical and sometimes, in the presence of oxygen, to a peroxide. Organometallic compounds give many radical-like reactions of course, and a possible oxidation mechanism for such compounds is a preliminary dissociation into radicals followed by oxidation of the radicals and the metal. 

Oximes are also good substrates for allylsamarium bromide addition.25 The Beckmann rearrangement product 44 was produced from oxime 43 in good yields when the ratio of allysamarium bromide to oximes was more than 3 1 (Equation (8)). This type of product was also obtained when the other allylic organometallic compounds were used. The reaction mechanism was proposed as shown in Scheme 13. 

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