Metal vapor synthesis techniques

Cobalt-silicon bonds, in hydridocobalt complexes, 7, 5 Cobalt—tin bonds, in hydridocobalt complexes, 7, 5 Co-catalyst effects, in olefin polymerization, 4, 1111 (—)-Goccinine, via Alder-ene reactions, 10, 593 Co-condensation sites, in metal vapor synthesis technique,... 

Cocondensation of nickel atoms, generated by metal vapor synthesis techniques with t-BuC=P, affords equal amounts of the isomeric sandwich complexes 94 and 95. The former compound features an T -phosphirenyl ligand in addition to an T -l -triphospholyl ring, whereas in 95 the metal is sandwiched between two i74-l,3-diphosphete units see Eq. (19).5,c... 

Metal-containing polymers may be produced by various methods, such as chemical reactions of precursors— in particular, reactions of metal salts in polymer solutions, the treatment of polymers with metal vapors, or the polymerization of various metal-monomer systems [1-4], Depending on the metal nature and the polymer structure, these processes lead to organometallic units incorporated into polymer chains, metal-polymer complexes, or metal clusters and nanoparticles physically connected with polymer matrix. Of special interest are syntheses with the use of metal vapors. In this case, metal atoms or clusters are not protected by complexones or solvate envelopes and consequently have specific high reactivity. It should be noted that the apparatus and principles of metal vapor synthesis techniques are closely related to many industrial processes with participation of atomic and molecular species [5]—for example, manufacturing devices for microelectronic from different metals and metal containing precursors [6]. Vapor synthesis methods employ varying metals and... 

The synthetic methods which have been used include modern versions of established methods of metal colloid preparation such as the mild chemical reduction of solutions of transition metal salts and complexes and newer methods such as radiolysis and photochemical reduction, metal atom extrusion from labile organometallics. And the use of metal vapor synthesis techniques. Some of these reactions have been in use for many years, and some are the results of research stimulated by the current resurgence in metal colloid chemistry. The list of preparative methods is being extended daily, and, as examples of these methods are described below, the reader will quickly be made aware that almost any organometallic reaction or physical process which results in the deposition of a metal is in fact a resource for the metal colloid chemist. The acquisition of new methods requires only the opportunism of the synthetic chemist in turning a previously negative result into a synthetic possibility. 

Pentacarbonyl iron is fairly inert to substitution reactions, and attempts to prepare Fe(CO)5- (CNR) (n = 1-5) by the direct reaction of Fe(CO)5 with isocyanides in Carius tubes has produced only the complexes Fe(CO)s (CNR) (n = 1 and 2). The products were obtained as mixtures that required separation. Other syntheses, including photochemical and trimethylamine N-oxide-promoted displacement of carbonyl groups, or other means, give the same products in variable yield. Procedures based on diiron nonacarbonyl and triiron dodecacarbonyl have produced similar results. The only zero-valent iron complex Fe(CO)5 (CNR) where n > 2 is the complex Fe(CNR)5 prepared either by metal vapor synthesis techniques or by sodium amalgam reduction of iron(II) bromide in the presence of isocyanide. ... 

Not surprisingly, in recent years the technique of metal vapor synthesis, in which the metal vapor and PF3 are cocondensed at liquid nitrogen temperatures, has found general application since PF3 is readily condensible (in contrast to CO) and the high volatility of the resulting metal-PF3 complexes facilitates their isolation (method H). 

The technique of metal vapor synthesis (method C) is obviously restricted to volatile ligands and has only been utilized so far in the synthesis of [Ni(PF3)2(PH3)2] and [Ni(PF3)3(PH3)]. 

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-... 

Highly reduced chromium binds dinitrogen, for example in fra i -[Cr(dmpe)2(N2)2] (4). Its crystal structure shows linearly bound N2 ligands (Cr-N, 187.4 pm, N-N, 112.2pm) and relatively short Cr-P distances (Cr-Pav, 229.6 pm). The related Cr(dmpe)3 exhibits similarly short Cr-P bonds (231.7 pm). These short Cr-P distances are thought to be due to n-Back Bonding to the phosphine ligand. Both Cr(dmpe)3 and Cr[P(OMe)3]6 were prepared by metal vapor synthesis see Metal Vapor Synthesis of Transition Metal Compounds). The same technique may also be used to prepare... 

Depending on the wavelength of radiation used, irradiation of Co2(CO)g produces either CO dissociation (at 250 nm) or cleavage into Co(CO)4 radicals (at 360 nm). The radical Co(CO)4 (2) itself has been detected by its Raman, infrared, UV-vis, and EPR see Electron Paramagnetic Resonance) spectra. It can be found by EPR when (1) is heated and sublimed on a 77 K cold finger in the EPR cavity, or it can be generated in a matrix at low temperature either by photolysis of (1) or by the metal vapor technique see Metal Vapor Synthesis of Transition Metal Compounds). 

Re arene complexes also result from application of the MVS technique to the extremely refractory Re metal (see Metal Vapor Synthesis of Transition Metal... 

It may not be out of place to mention that metal vapor deposition techniques that yielded highly promising results in organometallics (34, 54) may emerge as one of the exciting routes for the synthesis of metal alkoxide derivatives as well. To date, neither of these methods has been extended to the synthesis of heterometal alkoxides. 

Metal nanoparticles can be prepared in a myriad of ways, e.g., by pulse radiolysis [110], vapor synthesis techniques [111], thermal decomposition of organometallic compounds [112], sonochemical techniques [113,114], electrochemical reduction [115,116], and various chemical reduction techniques. Some of the most frequently used reducing agents include alcohols [117,118], citrate [119,120], H2 [121], borohydrides [122], and, more recently, superhydride [123]. The chosen experimental conditions determine the size, size distribution, shape, and stability of the particles. Because naked metal particles tend to aggregate readily in solution, stabilizing the nanoparticles is the key factor for a successful synthesis. Sometimes the solvent can act as a stabilizer, but usually polymers and surfac-... 

It is in the synthesis of organometallic complexes that the metal-atom technique shows its greatest utility. From metal vapors, many complexes may be synthesized on a macroscale that are difficult, if not impossible, to prepare by standard, wet-chemical techniques (64, 65). In this section, we shall illustrate the vast potential that the method has in this area, although, to be sure, it is evident throughout this entire review. 

The synthesis of MNCGs can be obtained by sol-gel, sputtering, chemical vapor-deposition techniques. Ion implantation of metal or semiconductor ions into glass has been explored since the last decade as a useful technique to produce nanocomposite materials in which nanometer sized metal or semiconductor particles are embedded in dielectric matrices [1,2,4,23-29]. Furthermore, ion implantation has been used as the first step of combined methodologies that involve other treatments such as thermal annealing in controlled atmosphere, laser, or ion irradiation [30-32]. 

We shall focus here on the synthesis of the isocyanide-containing polymer. Several reactions of the polymer with the metal vapors of Cr, Fe and Ni using a matrix-scale modeling technique, as well as synthetic-scale metal vapor methods, are then presented in order to demonstrate the reactivity of the isocyanide groups on the polymer. Finally, preliminary studies of the reactivity of the polymer-based metal complexes are described. 

The general technique of the metal vapor experiments described below was to co-condense the vapors of the transition metal with those of the chosen hydrocarbon or hydrocarbon mixtures. In this paper we briefly outline the technique of metal atom synthesis and then show how it can be applied to alkane activation reactions. 

Although the structures of these species were not determined, this metal vapor chemistry clearly showed that unsaturated hydrocarbons were viable reagents for lanthanides. Furthermore, this high energy technique showed that new regimes of organolanthanide complexes were accessible under the appropriate conditions. In addition, attempts to understand the synthesis of the products in reac-... 

Vapor deposition techniques have been extensively studied for the fabrication of metal and metal oxide structures. Indeed, the first reported tungsten oxide nanorods were essentially grown by this method. This groundbreaking synthesis of W02.72 leaves room for improvement, however, as it requires a reaction temperature of 1600°C in an argon atmosphere. Additionally, the researchers found the reaction product to be commingling WO2.72 nanorods and WO3 platelets rather than pure nanorods. Later,... 

Ullrafine particles (UFPs) of metal and semiconductor nitrides have been synthesized by two major techniques one is the reactive gas condensation method, and the other is the chemical vapor condensation method. The former is modified from the so-called gas condensation method (or gas-evaporation method) (13), and a surrounding gas such as N2 or NII2 is used in the evaporation chamber instead of inert gases. Plasma generation has been widely adopted in order to enhance the nitridation in the particle formation process. The latter is based on the decomposition and the subsequent chemical reaction of metal chloride, carbonate, hydride, and organics used as raw materials in an appropriate reactive gas under an energetic environment formed mainly by thermal healing, radiofrequency (RF) plasma, and laser beam. Synthesis techniques are listed for every heal source for the reactive gas condensation method and for the chemical vapor condensation method in Tables 8.1.1 and 8.1.2, respectively. 

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