Other Organometallic Reactions

A number of additional experiments have been carried out in an attempt to determine the overall mechanism for the catalytic decarbonylation reaction using [Rh(dppp)2]+. Since this reaction is a useful synthetic method and is a model for the discreet processes in other organometallic reactions, a detailed knowledge of the mechanisms and... 

A variety of other organometallic reactions starting from the homodimers are also reported in Sect. 4.2. 

For a recently-published book containing numerous examples of C-H and C-H activation as well as several other organometallic reactions involving pincer ligands, see D. Morales-Morales, The Chemistry of Pincer Compounds, Elsevier Amsterdam, 2007. 

The chapter ends with a rather miscellaneous collection of reactions such as one example of an electrocyclic ring closure 19. There are more important examples of ring closing olefin metathesis (RCM) and other organometallic reactions such as the Pauson-Khand reaction and co-trimerisation. 

However, not only starting problems were encountered in Barbier reactions and other organometallic reactions. Problems could also arise from, e.g. an uncontrolled addition of the reagents to the metal magnesium in a Barbier reaction (Table 2.24, Sect. 2.4.4, p. 66 see also the discussion of these reactions in Sect.4.4.2,p. 156). Such reaction conditions caused the formation of unexpected and often also undesired sideproducts. 

Besides ligand substitution reactions, various other organometallic reactions have been carried out according to the ETC mechanism (insertion, carbene transfer, isomerization, etc.) Moreover, it is possible to couple ETC catalysis with... 

Finally, these atom-transfer-ehain reaetions that are eommon in substitution reactions are, as ETC reaetions, also known for other organometallic reactions. 

Because of the complexity of the full mechanism, most theoretical studies concentrate on particular steps of the catalytic cycle. This chapter is thus organized by the different steps of the mechanism, rather than by reaction. Oxidative addition and reduction elimination have been studied also in the context of other organometallic reactions. Transmetalation is on the other hand specific of C-C bond formation processes, and because of this, it will be discussed in more detail. Our intention in this contribution is to review the present state of the research in the area. As wiU be seen, a significant part of the articles mentioned have been published after 2003, indicating the current high activity on the topic. Because of this, it is impossible to provide a definitive mechanistic picture. This is rather a progress report on a very active research field. This paper complements a recent review by some of us that focused on cross-coupling [19]. 

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. 

Reaction with halides or alkoxides of elements less electropositive than A1 affords a useful route to other organometallics ... 

Preparation of the appropriate optically active sulfmate ester is initially required for reaction with a Grignard or other organometallic reagent. If the method is to produce homochiral sulfoxides, the precursor sulfmate ester must be optically pure. An exception to this statement occurs if the reaction yields a partially racemic sulfoxide which can be recrystallized to complete optical purity. 

The reaction has also been performed with other organometallic compounds, for... 

Activation energies of thermal reactions in organometallic compounds have unfortunately not yet been measured. It would seem that the Group VI carbonyls would offer the best possibilities for such measurements, since their reactions are not complicated by competitive reactions. Unfortunately it cannot be said with confidence that these compounds are representative of aU other organometallic compounds as well. 

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