Halide precursors

Tnfluorometltylation of aryl, alkenyl, and alkyl halides can be accomplished by heating methyl fluorosulfonyldifluoroacetate and the appropriate halide precursor with copper(I) iodide at 60-80 °C in DMF [27 7] (equation 145). Similar trifluoromethylations of aryl, benzyl, and vinyl halides can be carried out with fluorosulfonyldifluoromethyl iodide and copper metal in DMF at 60-80 °C [2 75] (equation 146). 

Ottosson, M., Harsta, A., and Carlsson, J., Thermodynamic Analysis of Chemical Vapor Deposition of YBa2Cu307 from Different Halide Precursors, Prac. 11th. Int. Conf. on CVD, (K. Spear and G. Cullen, eds ), pp. 180-187, Electrochem. Soc., Pennington, NJ 08534 (1990)... 

Alkyl or hydride derivatives are formed by addition of a variety of Grignard reagents or sodium isopropoxide to the halide precursors. Cationic complexes may be obtained by the interaction with AgSbFg in the presence of an appropriate... 

The pyNP2 ligand was used for the synthesis of a molybde-num(0) dinitrogen complex (Scheme 11) (45). First the ligand was coordinated to a Mo(III) halide precursor to form [MoX3 (pyNP2)(thf)] (X Cl, Br ). Reduction of the Mo(III) complex... 

For less reactive metals, other synthesis schemes based on halide precursors are frequently employed. Bradley, Mehrotra, and Gaur have discussed alkox-ide synthesis in detail.34... 

Adsorption of Ag on the surface of PdO is also an interesting option offered by colloidal oxide synthesis. Silver is a well-known promoter for the improvement of catalytic properties, primarily selectivity, in various reactions such as hydrogenation of polyunsaturated compounds." The more stable oxidation state of silver is -F1 Aquo soluble precursors are silver nitrate (halide precursors are aU insoluble), and some organics such as acetate or oxalate with limited solubility may also be used." Ag" " is a d ° ion and can easily form linear AgL2 type complexes according to crystal field theory. Nevertheless, even for a concentrated solution of AgNOs, Ag+ does not form aquo complexes." Although a solvation sphere surrounds the cation, no metal-water chemical bonds have been observed. 

More recently, several arylcopper compound syntheses that make use of a soluble form of a copper halide precursor, CuBr-DMS (DMS = dimethylsulfide) in DMS as the solvent have been reported. Some of these compounds, such as [Cu4(QH5)4(DMS)2] [61] and [Cu4(C6H4Me-2)4(DMS)2] [62], appeared to be DMS adducts and were fully characterized by X-ray crystal structure determination (see Fig. 1.7). It is interesting to note that these structures contain two- and three-coordinate copper atoms in trans positions. These structures may be envisaged as ion-pairs comprising Cu(Aryl)2 anions bound to Cu(DMS) cations through the Cipso atoms. 

Several metal halide precursors have been applied in ALD processes, together with water as an oxygen source. However, the suitability of a particular metal halide for ALD depositions has been found to depend on the metal. Halide contamination of the film may cause problems at low deposition temperatures [45-47], although halides may be successfully used as ALD precursors. Liberation of HX (X = F, Cl, Br, I) during the deposition process may also cause problems, such as corrosion and etching. 

In 1994, Buzek et al. (109) reported that the allyl cation could be prepared from a variety of halide precursors, e.g., allyl chloride or cyclopropyl bromide, on SbF5 at cryogenic temperature, based on the infrared spectrum of the products. Those workers challenged BGW s claim of the persistent allyl cation based on the discrepancy between the isotropic 13C shift in the zeolite and that calculated at MP2/6-31G. This was one of the first examples of the use of chemical shift calculations to interpret (and in this case challenge) an NMR study of a species on a solid acid. 

Vibrational spectra assigned to surface 1-propyl groups following the decomposition of 1-propyl iodide or bromide have been obtained as follows, where the surface used, the halide precursor, and the decomposition temperatures are all indicated Al(100), iodide, 310 K (199) Cu(lll), bromide, 180 K (200) Cu(lll), iodide, 180 K (201) Cu(100), bromide, 185 K (193) and Cu(110), iodide, 165 K (202). The first four cases were investigated by VEELS, and the fifth one by RAIRS. The band positions observed, the band intensities, and their probable vibrational assignments are listed in... 

Polyglymes offer a viable alternative as solvents to the potentially carcinogenic HMPA.1871188 Alkyl and phenyl sulfides were prepared from the reaction of suitable aryl halide precursors and an excess of sodium thiolates in tetraglyme.188 By the same procedure 2-(alkylthio)-substituted (alkyl = Me(CH2)n n = 3, 15,17) quinolines, pyrimidines and pyrazines were prepared from the corresponding chlorides.187... 

Catalytic procedures (introduced by Kuivila and Menapace92) are easier to conduct and the tin hydride concentration is more easily controlled. A catalytic amount of tributyltin hydride or tributyltin chloride is mixed with the radical precursor, the alkene acceptor and a stoichiometric quantity of a coreductant such as sodium borohydride93 or sodium cyanoborohydride.29 Over the course of the reaction, the borohydride continuously converts the tin halide to tin hydride. The use of the catalytic procedure is probably restricted to halide precursors (tin products derived from other precursors may not be reduced to tin hydrides). This method has several advantages over the standard procedures (i) it is simple to conduct (ii) most functional groups are stable to the coreductants (especially sodium cyanoborohydride) (iii) the tin hydride concentration is known, is stationary (assuming that the tin halide is rapidly reduced to tin hydride), and can be varied by either changing the concentration of the reaction or the quantity of the tin reagent (10% is a typical value, but lower quantities can be used) and finally, (iv) the amount of tin hydride precursor that is added limits the amount of tin by-product that must be removed at the end of the reaction. 

Preparation from Other Precursors. Alkyl cations can be formed not only from halide precursors (the earlier investigation of generation from alkyl fluorides was later extended to alkyl chlorides, bromides, and even iodides) but also from alkenes in superacids like HF-SbF5 [Eq. (3.10)]. 

Scheme 10.18 illustrates the key features of the intramolecular reaction in general and also the specific radical intermediates in the mechanistic study [18]. After initial radical formation from a suitable halide precursor, in the vast majority of cases using Bu3SnH and... 

The factors that effect the partition of a radical (resulting from reaction of the halide precursor with AIBN-BusSnH) between three-carbon Dowd-Beckwith ring expansion... 

For laboratory use, the dehydration of LnCl3 (H20)x (x = 6,7) using NH4C1 is the favorite method of preparing anhydrous lanthanide chlorides [96b]. However, simple thermal dehydration, as accessible to lanthanide trif-lates, leads to the formation of undesirable lanthanide oxychlorides. Because the Ln-halide precursor is insoluble in aliphatic and aromatic hydrocarbons, the preparation of organolanthanides via salt metathesis is performed in coordinating solvents such as THF. 

Deoxysugars, nucleosides and related molecules have also been prepared from hydroxy-protected, halogenated precursors using tributyltin hydride 55,58,. Thus in one example, the key step of the preparation of a 3 -deoxy derivative of S-formycinyl-L-homocysteine was the reduction of a halide precursor (equation 7)62. 

Starting compounds usually are metal halide precursors and alkali salts of the S ligands. Precipitation of alkali halides favors the formation of the [M(S )] complex fragments. 

Synthetic routes leading to two series of (COT)lanthanide(III) scorpio-nate mixed sandwich complexes were reported. The early lanthanide derivatives (COT)Ln(Tp) and (COT)Ln(TpMe2) (Ln = Ce, Pr, Nd, Sm) were obtained by reacting the dimeric halide precursors [(COT)Ln(p-Cl)(THF)]2 with KTp or KTpMe2. For small lanthanide ions (COT)Ln(Tp) (Ln = Er,... 

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