Reactions Involving Organometallic Compounds

Reactions Involving Organometallic Compounds 1. Reaction of lithium alkyls with organic halides 

The first example of chemically induced raultiplet polarization was observed on treatment of a solution of n-butyl bromide and n-butyl lithium in hexane with a little ether to initiate reaction by depolymerizing the organometallic compound (Ward and Lawler, 1967). Polarization (E/A) of the protons on carbon atoms 1 and 2 in the 1-butene produced was observed and taken as evidence of the correctness of an earlier suggestion (Bryce-Smith, 1956) that radical intermediates are involved in this elimination. Similar observations were made in the reaction of t-butyl lithium with n-butyl bromide when both 1-butene and isobutene were found to be polarized. The observations were particularly significant because multiplet polarization could not be explained by the electron-nuclear cross-relaxation theory of OIDNP then being advanced to explain net polarization (Lawler, 1967 Bargon and Fischer, 1967). 

Tertiary amines also depolymerize lithium alkyl tetramers and hexamers and can be used to trigger reactions with alkyl halides (Lepley, 1968). However, when triethylamine is used to initiate the butyl 

Polarization is found in reactions involving chlorides. 1,1-Dichloro-2,2-dimethylcyclopropane (26) reacts with lithium ethyl in benzene-ether solution (40°) giving mainly l-chloro-2,2-dimethylcyclopropane (27 X=H) and 3-methyl-l, 2-butadiene (28) both of which are polarized (Ward et al., 1968). If n- or t-butyl lithium are used in the reaction, the butene produced by disproportionation shows only net polarization. 

Studies of alkyl halide-lithium alkyl reactions have been almost wholly concerned with proton polarization. The one exception to date is an investigation of polarization in the reaction of n-butyl lithium with p-fiuorobenzyl chloride giving p,p -difluorobibenzyl (A/E multi-plet) and l-fluoro-4-pentylbenzene (E/A) (Rakshys, 1970). Surprisingly H-polarization is not observed. 

---

Thio and thiol substituents Reactions with dipolarophiles Atropisomeric 1,2-dithiole-3-thiones Reactions involving organometallic compounds... 

This chapter summarizes the literature to approximately mid-1998 pertaining to photochemical and photoinduced (organic) reactions in SCF solvents. Photochemical reactions involving organometallic compounds in SCF solvents have been extensively studied by Poliakoff [20], and are discussed in Chapter 4.2. In this chapter the emphasis is on reaction chemistry in which stable products are formed and isolated, and how the unique features of the SCF medium influence reaction yields, rates, and/or selectivities. 

Some Reactions of Aromatic Heterocycles Involving the Catalytic Action of the Cyanide Ion E. Hayashi, Shizuoka Yakka Daigaku Kaigaku, 25-Shunen Kinen, 1978, 1-12. Reactions of Organometallic Compounds in the Heterocyclic Field A. Marxer, Led. Heterocycl. Chem., 1976, 3, 131-139. 

Modern electrochemical methods provide the coordination chemist with a powerful means of studying chemical reactions coupled to electron transfer and exploiting such chemistry in electrosynthesis. In addition, the electrochemical generation of reactive metallo intermediates can provide routes for the activation of otherwise inert molecules, as in the reduction of N2 to ammonia,50 and for electrocatalyzing redox reactions, such as the reduction of C02 to formate and oxalate,51 the oxidation of NH3 to N02-,52 and the technologically important oxidation of water to 02 or its converse, the reduction of 02 to water.53 Electrochemical reactions involving coordination compounds and organometallic species have been extensively reviewed.54-60... 

Streitwieser and co-workers have extended their measurements of equilibrium acidities in cyclohexylamine to determination of exchange rates.69 They have made quantitative correlations between exchange rate and the pKa s determined by equilibrium methods for various aromatic compounds and have thus been able to verify that the Bronsted relation holds for these substances and to find Bronsted coefficients a for various types of compounds. A third method for evaluating p/Ca of weak acids, which has been used by Applequist70 and by Dessy,71 involves the study of exchange reactions of organometallic compounds (Equations 3.54 and 3.55). 

Among the many reactions of organometallic compounds, ones involving insertion and elimination of ligands are important in applications to synthesis and catalysis. An example of a carbonyl insertion is ... 

Applications of nuclear magnetic 179 resonance to the study of organo- (380) metallic compounds Reactions involving organometallic 20 compounds of rhodium, iridium, (77) palladium and platinum a survey of NMR studies... 

In this chapter, we have considered just a few types of reactions of organometallic compounds, principally the replacement of CO by other ligands and the reactions involved in syntheses of carbene and carbyne complexes. Additional types of reactions will be discussed in Chapter 14. We conclude this chapter with two examples of how spectral data may be used in the characterization of organometallic compounds. Further examples can be found in the problems at the end of this chapter and in Chapter 14. 

Some of the most important reactions of organometallic compounds involve a change in coordination number of the metal by a gain or loss of ligands. If the formal oxidation state of the metal is retained, these reactions are considered addition or dissociation reactions if the formal oxidation state is changed, they are termed oxidative additions or reductive eliminations. 

Thus the many reactions of organometallic compounds may involve organic group(s) only, inorganic ligand(s) only, the metal only, or the... 

---