Preparation of organometallics

Thomson w Click Organic Interactive to learn more about the preparation of organometallics and their use in coupfmg reactions. 

Ge, P, As, Sb, and Bi, can also be prepared in this manner." Except for alkali metal alkyls and Grignard reagents, the reaction between RM and M X is the most conunon method for the preparation of organometallic compounds." ... 

A rotary apparatus is used for metal evaporation as shown in Fig. 1. Similar equipment is employed for the preparation of organometallics. For Au clusters, Au metal is evaporated from a resistively heated W boat onto an ethanol film, in which the reactants, e.g., AufPAr IX and/or PAr, are dissolved (see Table 1, method B, 8.2.2.2). 

The use of organotin compounds for the preparation of organometallics and organometalloids appears to be quite versatile.9 For example, alkyltetrafluorophosphoranes have been obtained from tetraalkyltin compounds and phosphorus(Y) fluoride,10 phenylmercury(II) chloride from tetraphenyltin and mercury(II) chloride,11 and divinylbromoarsine from ( -C4H9)2-Sn(CH=CH2)2 and arsenic (III) bromide.12... 

Synthesis with sacrificial electrodes is employed as a direct method in several other preparations of organometallic compounds and complexes. 3-Hydroxy-2-methyl-4-pyrone derivatives of Sn 1 (and of Zn, Cu, In and Cd as well) were prepared using the metal as an anode. The low oxidation state Sn(II) compound is obtained by direct electrolysis134. 

Ultrasound is widely used for the preparation of organometallic compounds from reactive metals [67]. Here the mode of action of ultrasound is twofold ... 

TABLE 1. A survey of the standard methods applied to the preparation of organometallic compounds three crosses mean generally applicable , two restricted, though important scope of appU-cabiUty and one narrow scope ... 

Ultrasound activation of metals. Since its discovery as an activation technique some fifty years ago, sonication has been demonstrated to be of general use for the depassivation of different metals. In this case, the activation consists in cleaning the surface of the metal, making possible better contact between the reagents. Probably the most important applications of ultrasonic irradiation are the direct preparation of organometallic reagents and different metal-assisted reactions, for instance in aqueous media . 

The first report of the preparation of organometallic compounds by direct reaction between metals atoms and organic ligands came in 1969 (727). Research into synthesis using metal atoms has expanded steadily since then and now seems likely to increase very rapidly as the necessary equipment becomes commercially available.1 The field has been reviewed in part before (55, 67, 78a, 84a, 129), but no comprehensive review of the organometallic aspects has yet been published. 

The most widely used method for the preparation of organometallic compounds of the heavier alkali metals is from the corresponding organo-lithium reagent and an alkoxide. 

Preparation of Organometallic Compounds. Metals with Organic Halides... 

The more reactive allylic and benzylic halides present a problem—not so much in forming the organometallic derivative as in keeping it from reacting further with the starting halide. An often unwanted side reaction in the preparation of organometallic compounds is a displacement reaction, probably of the Sn2 type ... 

The Grignard reaction is often one of the first reactions encountered for the preparation of organometallic compounds. As such it provides a method for the conversion of an alkyl bromide to an alkane. From the example shown below it is seen that the overall oxidation level change from the organic reactants to the products is from 0 to —2, so a reduction has occurred. Magnesium is the reductant and is itself oxidized from 0 to +2 oxidation state. The actual reduction takes place in the first step of the process in which the C-Br bond is converted to a C-Mg-Br bond. The reaction with water is merely a hydrolysis that does not change the oxidation state of carbon. 

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