Metal exchange reaction

There have been other reports of immobilization of Hoveyda-type complexes on polystyrene supports. Blechert and co-workers have extended their methodology for immobilization of NHC complexes to the preparation of 172 (Scheme 70). The supported NHC ligand was prepared in the same manner as for 166, the metal complex then being attached to the support via a ligand exchange reaction. Metal loadings of 0.7mmolg resin were obtained. The authors also report a metal complex 174 bound to the support via... 

Alkynyl anions are more stable = 22) than the more saturated alkyl or alkenyl anions (p/Tj = 40-45). They may be obtained directly from terminal acetylenes by treatment with strong base, e.g. sodium amide (pA, of NH 35). Frequently magnesium acetylides are made in proton-metal exchange reactions with more reactive Grignard reagents. Copper and mercury acetylides are formed directly from the corresponding metal acetates and acetylenes under neutral conditions (G.E. Coates, 1977 R.P. Houghton, 1979). 

Organic compounds M—R and hydrides M—H of main group metals such as Mg, Zn, B, Al, Sn, SI, and Hg react with A—Pd—X complexes formed by oxidative addition, and an organic group or hydride is transferred to Pd by exchange reaction of X with R or H. In other words, the alkylation of Pd takes place (eq. 9). A driving force of the reaction, which is called transmetallation, is ascribed to the difference in the electronegativities of two metals. A typical example is the phenylation of phenylpalladium iodide with phenyltributyltin to form diphenylpalladium (16). 

Two types of hydrogen replacement are discussed here (1) the base-induced hydrogen-deuterium exchange reactions and (2) the hydrogen-metal exchange reactions. 

In conclusion, it appears that in neutral or weakly acidic conditions only the methyl in the 2-position shows pseudoacidic behavior. The same conclusion can be drawn from the base-induced hydrogen-metal exchange reactions discussed in Section III.5.B. 

Catalytic amounts of mercuric chloride are usually employed in this preparation. Aluminum isopropoxide is a useful Meerwein-Potmdorf-Verley reducing agent in certain ester-exchange reactions and is a precursor for aluminum glycinate, a buffering agent (see Alkoxides, metal). 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

In this case the efficiency of metal complex modifiers is controlled not only by their thermal stability, the nature of the metal and the ligand used, but depends considerably on the reactions in the solution, mainly on exchange reaction like Me,L -i- Me = MeU + Me L, which variously affect the... 

The tlrree impurities, iron, silicon and aluminium are present in the metal produced by the Kroll reduction of zirconium tetrachloride by magnesium to the extent of about 1100 ppm. After dre iodide refining process tire levels of these impurities are 350, 130 aird 700ppm respectively. The relative stabilities of the iodides of these metals compared to that of zirconium can be calculated from the exchange reactions... 

The separation of niobium from tantalum tluough the gaseous chlorides is carried out at higher temperature, about 900 K, and it is therefore to be expected, as is the case, that the thermodynamic data will provide a useful guide. These metals form a number of chlorides, mainly the ui- tetra- and pentachlorides. These latter are much more volatile than the tetrahalides, and the exchange reaction at 900 K... 

The halogen-metal exchange reaction was pioneered by Gilman and co-... 

The metal-halogen exchange reaction is useful in the synthesis of numerous perfluoroalkylmagnesium halides, some of which are shown in Table 2... 

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