Allenes metalation

S.8.2.7.6. a-Alkenyl Complexes by Nucleophilic Attack on n-Alkyne- and Allene-Metal Complexes. 

This situation may be explained by stronger interaction between the middle carbon atom and the metal atom. Such interaction is caused by the presence of two mutually perpendicular bonding and antibonding n orbitals. The terminal carbon atoms have only n and tt orbitals. This is equivalent to the interaction of the metal with the uncoordinated double bond of the allene which also leads to the change of distance d between carbon atoms. The smaller distance is a result of a smaller atomic radii of the middle allene carbon atom which forms two double bonds. The distance and angles in the allene-metal complexes are given in Table 6.25. Structures of some allene complexes are depicted in Figure 6.24. 

Protonation of the acetylenes (373) gives crystalline dihapto-slhne salts (374). The latter react with various nucleophiles by attack at either carbon of the co-ordinated double bond. Since the free allenes are fairly inert to attack by nucleophiles, this exemplifies the influence that metals have on co-ordinated organic ligands. These allene-metal complexes conceivably play... 

Allen S M and Cahn J W 1979 Acta. Metall. 27 1085 see also Ohta T, Jasnow D and Kawasaki K 1982 Phys. Rev. Lett. 49 1223 for the model A scaled structure factor... 

Allen G L ef a/1986 Small particle melting of pure metals Thin Solid Films 144 297... 

Allen G L, Gille W W and Jesser W A 1980 The melting temperature of microcrystals embedded in a matrix Acta Metall. 28 1695... 

Note 1. The lithiation of monoalky1al 1 enes is not completely regiospecific. The ratio of a- to ylithiated allene varies from about 80 20 for methyl-allene to 93 7 for hexylallene. tert.-Butylallene, however, is metallated exclusively on the terminal carbon atom. 

The alkylations proceeded much more slowly, when ethyl- or butyllithium in diethyl ether, prepared from the alkyl bromides, had been used for the metallation of allene, in spite of the presence of THF and HMPT as co-solvents. 

Similar results are probably obtained when the metallation of the allenic ether is carried out with butyllithium in hexane-THF or diethyl ether. 

One of the most dramatic developments in the chemistry of N2 during the past 30 years was the discovery by A. D. Allen and C. V. Senoff in 1965 that dinitrogen complexes such as [Ru(NH3)5(N2)1 could readily be prepared from aqueous RUCI3 using hydrazine hydrate in aqueous solution. Since that time virtually all transition metals have been found to give dinitrogen complexes and several hundred such compounds are now characterized.Three general preparative methods are available ... 

Selectivity depends importantly on the catalytic metal. A number of selectivity series have been determined for simple olefins, and the presumption is that the sequence holds for more complex polyenes as well. Selectivity for the reduction of allene to propylene declined with metal in the order palladium... 

The polymerization filling was effected by the ion-coordination mechanism [17-19]. The monomers were ethylene, propylene, allene, os-butylene, butadiene. The fillers were mineral materials such as ash, graphite, silica gel, glass fibers. The ultimate aim of filler conditioning prior to polymerization is to secure, on its surface, metal complex or organometallic catalysts by either physical or chemical methods [17-19],... 

An example of a serendipitous discovery in a field related to diazo chemistry is the first in vitro product of a reaction of molecular nitrogen with a transition metal complex (Allen and Senoff, 1965). As discussed in the context of diazo-metal complexes (Zollinger, 1995, Sec. 3.3), the metal —N2 bonds are similar to C —N2 bonds in organic diazo compounds. The paradigm that N2 is (almost) inert in chemical reactions probably explains why it took so long for N2 complexes to be discovered. ... 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

Mancy, K.H. Allen, H.E. A Controlled Bioassay System for Measuring Toxicity of Heavy Metals. U.S. Environmental Protection Agency Washington D.C., 1977. 

As is the case with assessments of the toxicity of dissolved trace metals, the development of sediment quality criteria (SQC) must be based on the fraction of sediment-associated metal that is bioavailable. Bulk sediments consist of a variety of phases including sediment solids in the silt and clay size fractions, and sediment pore water. Swartz et al. (1985) demonstrated that the bioavailable fraction of cadmium in sediments is correlated with interstitial water cadmium concentrations. More recent work (e.g., Di Toro et al, 1990 Allen et al., 1993 Hansen et al, 1996 Ankley et ai, 1996, and references therein) has demonstrated that the interstitial water concentrations of a suite of trace metals is regulated by an extractable fraction of iron sulfides. 

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