Metals atom vapors

The experimental apparatus used consisted of a stationary metal atom-vapor reactor which has been detailed in the literature earlier. (39) Metal was evaporated (-0.1 to 0.5 g) and codeposited at -196°C with excess organic solvent vapor (- MO-150 mL). The frozen matrix was allowed to warm under controlled conditions, and upon melting stirring was commenced. After warming to room temperature stable colloidal solutions were obtained and syphoned out under N. ... 

Fig. 5 Diagram showing the major aspects of metal atom vapor deposition on a SAM...

By reactions of metal atom vapors with alcohols 337... 

The development of metal atom vapor technology over the last 15 years has made available to the chemist a new and useful synthetic technique. A number of novel transition metal compounds have been isolated by the method, particularly in the field of organometallic chemistry. However, the use of vaporized metal atoms for the synthesis of metal alkoxides and phenoxides by condensation into the neat alcohol has been only briefly mentioned in the literature.27... 

Another non-conventional preparative route to bimetallic catalysts has been developed where metal atoms (vapors) have been trapped at low temperature in solvating media. (A review has recently appeared).(17) By solvating two metals at the same time (eg. Co in toluene and Mn in toluene), followed by warming, bimetallic clusters/particles form. In the presence of a catalyst support, surface -OH groups can have a dramitic affect on the structure of the small bimetallic cluster produced. For example, with Co and Mn, a layered structure of MnOx covered by Co° in a particle of about 25 A was formed.(iS) With Fe and Co combinations, a layer of FeOx followed by Fe°Co° alloy and a surface rich in Co° was formed. (19)... 

The synthesis of large clusters such as [A Ris]3- (Chapters 2 and 3) proceeds by A1 atom cluster-core build up. Cluster-core growth is terminated at some point by external ligands. The method of Schnockel is a variation of metal-atom vapor-deposition techniques and relies on (a) the reversibility of the equilibrium between the liquid metal, e.g., Al, and gaseous metal halide, e.g., AICI3, with gaseous subhalide, e.g., A1C1 (b) the shift in equilibrium position with temperature and (c) competitive rates at similar temperatures of subhalide disproportionation to metal... 

Metal-atom vapor synthesis techniques have been successfully applied to the preparation of metaUacarbaboranes, that is, reaction type M - - C -I- B. A disadvantage is that product distribution tends to be nonspecific, for example, when Co metal is vaporized by electrical heating and cocondensed at -196 °C with cyclopentadiene, B5H9, and the alkyne MeCsCMe, l-(CpCo)-2,3-Me2-2,3-C2B4H4, l,7-(CpCo)2-... 

Figure 1 Schematic diagram of a cocondensation metal atom (vapor) reactor...

Formation of Carbon-Transition and Inner Transition Metal Bond 125 5.8.2.9. from Organic Halides, Tosylates and Acetates 5.8.2.9.3. by Reaction with Metal-Atom Vapors... 

S.2.9.3. t] o-Alkyl-, -Aryl-, Acyl- and Silyl Metal Complexes by Reaction of Metal-Atom Vapors. 

Cocondensation of metal-atom vapors and organic ligands yields transition-metal hydrides as well as other organometallics (see Table 1). The bulk metal is vaporized at a controlled rate by resistance heating, laser heating or electron bombardment under vacuum [<10 torr (<0.1 Pa)]. The atoms condense either on the cooled walls (< — 100°C) of the vacuum chamber with an excess of the organic compound or into a solution of the compound in an inert solvent. Yields of hydride often are based on the amount of metal evaporated. 

Oxidative addition of H—C bonds to transition metals, which also is referred to as an activation of the H—C bond, is of scientific and technological importance. " (See 1.10.2 for activation of H—C bonds by metal-atom vapors.) Intramolecular oxidative addition of H—C bonds (cyclometallation) occurs, but organic functional... 

Cyclopentadiene reacts with transition metals by oxidative addition of one H—C bond at the saturated carbon. Metal-atom vapors of Mo and W codeposit with cyclopentadiene to form (h -C5Hj)2MH2. Irradiation of Mo(CO)j with cyclopentadiene in isooctane yields (h -C5H5)Mo(CO)2C5H2-h ) that involves overall H transfer between ligands. 

Figure 14 Allylic Grignard reagent formed from the corresponding allyl chloride using magnesium activated by the metal atom vaporization method.

Gilman catalyst (12). 57 58 metal atom vaporization. 60 ultrasound. 61 vitridc addition. 58... 

Alternatively, Mo(r -arene)2 complexes (arene = C HjCH, C HsF, C HjCl, C6H5(NMc2), CfjH5COOMe) have been prepared by metal atom vapor synthesis from molybdenum metal and arene [50,51]. 

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