Other Metal Systems

Copper has also found wide use however, it has generally only been found to be applicable to heteroatom-carbon coupling reactions when employing boronic acids as coupling partners, now known as the Chan-Lam coupling.  

---

More effort has probably been devoted to study of the corrosion and passivation properties of Fe-Cr-Ni alloys, e.g. stainless steel and other transition-metal alloys, than to any other metallic system [2.42, 2.44, 2.55, 2.56]. The type of spectral information obtainable from an Fe-Cr alloy of technical origin, carrying an oxide and contaminant film after corrosion, is shown schematically in Fig. 2.13 [2.57]. 

An advantage of nickel catalysts over other metal systems is that the properties of the active species can easily be tuned by the addition of suitable ligands. For example, the presence of PPhj was shown to have a direct influence on the regiochem-istry of hydroalumination of 1,1-dimethylindene la [33]. While the reaction of BU2AIH with la gave a 4 1 mixture of regioisomeric products 13a/13b after deuterolytic workup, the same reaction carried out in the presence of PPh, yielded 13a and 13b in a ratio of >99 1 (Scheme 2-14). 

The coefficient, p, of the viscosity resisting dislocation motion is the shear stress at the glide plane, x divided by the frequency of momentum transfer, v. The maximum value that x can have is about Coct/47i, and as mentioned above v = 1013/sec for the Al atoms,so p = Coct./47rv = 4x 10 3 Poise.This is comparable to the dislocation viscosity coefficients in other metallic systems. Another view of the viscosity is Andrade s theory in which ... 

Small ey(Ib) that cobalt and niobium clusters react in a very selective fashion with deuterium was rapidly followed by similar studies on a variety of other metal systems. Three groups simultaneously reported similar dramatic behavior for iron c usters( 2b, 3b). Di hydrogen or di deuteri urn addition reactions have been reported for vanadium( 3e), i ron(lc,2a-d,3b), cobalt(lb),... 

Methods for the generation and use of enantiomerically pure vinylketene complexes have been well developed in recent years. This has allowed stereocontrol to be exerted over subsequent reactions to yield optically active organic or organometallic products. It has also allowed investigations to be carried out into the reaction mechanisms of several fundamental processes. This area is currently ripe for further exploration and would be of particular interest in its application to other metal systems. We trust that the work presented here will serve as a platform for further new and exciting discoveries. 

There are a wide range of papers using electron spectroscopic techniques to study the interaction of oxygen with silver and other metal systems (298), but it has proved difficult to differentiate between the various oxygen species and also OH- using these techniques (Section VII). This is likely to improve in the future as the understanding of the detailed analysis of the bands is refined. 

Although the distinction is not always clear, ternary nitrides (and nitrides in general) often are classified into two groups (1) intermetallic-type and (2) ionic/covalent-type. Intermetallic nitrides are those in which metal-metal (M-M) interactions are dominant and where the nitrogen atoms are interstitial within the metal array.3 Because these phases are stabilized by M-M interactions, the structure and physical properties are similar to those of many other metallic systems, such as alloys, metals, and... 

Comparisons with Other Metal Systems. Although as complete a series as that reported here is not available for other metal systems, the limited data reviewed in the literature (15, 16, 50) suggest that both steric bulk and electronic effects will influence the M-P bond length. As the bulk of L is changed, the percentage s character in the M-P bond also changes (51, 52). The spectroscopic trends whenX is varied... 

Triply bridging orf/io-phenylene complexes sometimes arise in curious ways. In the reaction of Os3(CO)10(MeCN)2 with salicylaldehyde benzy-limine one would naively expect that coordination would be through N and O atoms as with other metal systems. The first formed compound (40, Scheme 6) results from ortho metallation while, of the three isomeric decarbonylation products (41 to 43), compound 43 contains only Os—C bonds to the ligand and is a ring-substituted version of Os3H2(C6H4)(CO)9 (Scheme 6) (237). 

Clearly, the YETI force field is a very complicated approach to solving equally complicated problems. As such, it illustrates well the problems that must be addressed in inorganic modeling that simply do not occur in organic modeling. The primary problem addressed in Vendani s work is the variable coordination number of Zn and Co in carbonic anhydrase. The YETI program obviates some of these problems, but it is not apparent that the solution can be transferred to other metal systems. Nonetheless, useful results are obtained for the metalloenzymes and model systems for which the method was developed. 

Although catalytic preparations of cyclopentadienones with other metal systems are known, chemose-lectivity is often a problem. For example, the reactions of 2-butyne, 3-hexyne and diphenylacetylene with [(CO)2RhCl]2 at 80 °C give mixtures of hexasubstituted benzenes, metal-complexed, tetrasub-stituted cyclopentadienones and quinones. An exception is the preparation of the stable tetrakis(trifluo-romethyl)cyclopentadienone from the alkyne the unusual electronic properties of the product make this result lack generality. 

A number of other mechanistic sequences are thought to occur in alkyne trimerizations mediated by other metal systems. Catalysts derived from Co2(CO)s follow a characteristic sequence of steps that involves exclusively dinuclear complexes (Scheme 26). The nature of the final (alkyne)3C02(CO)4 intermediate, a so-called flyover complex, is supported by both X-ray crystal structure data as well as its involvement in forming other products besides benzenes. These dinuclear cobalt systems are note-... 

Cyclotrimerization and cyclotetramerization of alkynes to form benzene and cyclooctatetraene derivatives was first achieved with various nickel catalysts26. Several other metal systems are also active and numerous applications have been reported3 5. Various concerted or stepwise reaction paths have been suggested3,5,2 -29. 

Other metal systems studied include IrSu2 and PtSn2 which have the CaFa lattice [23. Recoil-free fraction and lattice dynamical studies have been made on SnAs, SnSb, SnTe, and SnPt [237] and on NbaSn [238,239]. 

The initial tests of the sodium dispersion-metal halide system were made with ferric chloride, fortunately, and with a nonaqueous solvent in which ferric chloride was soluble. Thus, ferric chloride was present as a solution and, consequently, presented maximum surface for contact with the sodium particles. This feature, coupled with the lower activation energy requirements, permitted the reaction to proceed at temperatures well below room temperature and established the operability of the method. The success of the initial (ferric chloride) tests lent encouragement to tests on other metal systems and prompted continued investigations when the initial runs at lower temperatures failed. The discovery of the threshold, or trigger, temperature for nickel (II) chloride reduction paved the way for successful reduction of other metal halides such as manganese (II) chloride, cobalt (II) chloride, and cadmium bromide. 

Co using their respective metal nitrate and glycine mixture. Nickel was chosen as a model to successfully verify the thermodynamic predictions. It can be concluded from the results and discussion that the fuel to oxidizer ratio, (p, is an important parameter in SCS systems and significantly influences the synthesized nanoparticles. The q> value not only affects the combustion temperature but also the nature of the solid product (metal or metal-oxide), porosity and crystalhte size. It is anticipated that the other metal-systems (Cu and Co) will also follow a similar trend. The properties of the synthesized nanoparticles can be controlled and fine-tuned by adjusting the fuel to oxidizer ratio in SCS processes. 

Abstract The activation of C-H bonds by oxidative addition in about 30 different substrates has been examined with three closely related metal species, [Tp RhL], where L = CNneopentyl, PMes, and P(OMe)3. Kinetic studies of the reductive elimination of R-H provided data to ascertain the relative metal-carbon bond strengths for a wide range of compounds. Trends in these bond strengths reveal that there are two classes of C-H substrates parent hydrocarbons and substituted methanes. DPT calculations are used to support the observed trends, and some generalizations are made by comparison to other metal systems. 

Figure 8 shows the DPT-calculated version of bond strength trends for Tp Rh[P(OMe)3](R)H complexes. As with the previous two cases, the slopes of the lines are overestimated by about 10%. Does this mean that DFT calculations may be expected to also overestimate the slope in other metal systems Eisenstein and Perutz made a series of such calculations for both Ti(R)(silox)2(NHSif-Bu3) (silox = OSit-Bu3) and the simplified TpRh(CNMe)(R)H systems [21]. For both systems, about a dozen substrates were considered, and lines were produced with slopes of 1.08 and 1.22, respectively. However, both of these correlations included data for a-mesityl and allyl, and these data can be seen to lie above the correlation for the parent hydrocarbons. From the current studies, we now know why these data... 

Although exfoliation corrosion has been reported in a few other metal systems, incidents of this form of corrosion tire few and presumably not of practical importance. Therefore, no attempts have been mtide to develop and standardize specific tests for detecting susceptibility to exfoliation for these other metals. The following notes from published literature may be of interest to some readers. 

---