Metals, activated condensation

Maitani MM, Daniel TA, Cabarcos OM, Allara DL (2009) Nascent metal atom condensation in self-assembled monolayer matrices coverage-driven morphology transitions from buried adlayers to electrically active metal atom nanofilaments to overlayer clusters during aluminum atom deposition on alkanethiolate/gold monolayers. J Am Chem Soc 131 (23) 8016-8029... 

Metal films condensed in a high vacuum have, usually, a much lower catalytic activity than films condensed in a low pressure of an inert gas.3 The films condensed in the gas had an oriented structure, with the (110) face parallel to the backing in the case of nickel, the (111) face in the case of iron. There was little, if any, definite orientation in the films condensed in vacuo. It has been suggested that the increased catalytic activity is, in part at least, due to the special spacing on the exposed crystal faces but there may be other reasons, perhaps the presence of linear interfaces between the bare metal and the parts covered by adsorbed gas, or a larger real surface. The suggestion is interesting, however, and now that it is possible to make faces in selected crystal planes, to the practical exclusion of others, the study of the catalytic activity of special crystal faces does not seem beyond the bounds of possibility. 

Allenylidene triiron clusters such as that shown in Fig. 21b were obtained upon C-C bond cleavage in cumulenes. The first complex of this type was, however, obtained by reacting Fe(CO)5 and [C2C(Bu 20] in the presence of Me3NO, through chemical CO activation and metal fragment condensation. ... 

The activated species of the sol-gel precursors continue to react with each other to form colloidal solutions of oligomeric species. The precursors containing hydroxyl groups bonded to metal atoms condense according to olation, oxolation, and/or alcoxolation routes catalyzed under acidic and basic... 

The increase in activity in the field of organotin hydrides is mostly due to the facility of addition of the tin-hydrogen bond to unsaturated systems and to the multiple mechanistic investigations of the hydrostannation reaction. Hev is a number of organometallic reactions, i.e., addition to transition metal complexes7 condensation with metal alkyls yielding tin-metal derivatives and with metal amides for synthesis of compounds with longer tin chains. 

Condensation catalysts include both acids and bases, as well as organic compounds of metals. Both tin(II) and tin(IV) complexes with carboxyhc acids ate extremely useful. It has been suggested that the tin catalyst is converted to its active form by partial hydrolysis followed by reaction with the hydrolyzable silane to yield a tin—sdanolate species (eqs. 22 and 23) (193,194). 

A number of disinfectants apparentiy owe their activity to formaldehyde, although there is argument on whether some of them function by other mechanisms. In this category, the dmg with the longest history is hexamethylenetetramine (hexamine, urotropin) [100-97-0] which is a condensation product of formaldehyde and ammonia that breaks down by acid hydrolysis to produce formaldehyde. Hexamine was first used for urinary tract antisepsis. Other antimicrobials that are adducts of formaldehyde and amines have been made others are based on methylolate derivations of nitroalkanes. The apphcations of these compounds are widespread, including inactivation of bacterial endotoxin preservation of cosmetics, metal working fluids, and latex paint and use in spin finishes, textile impregnation, and secondary oil recovery (117). 

A partially reduced quinoline derivative with antiulcerative and antisecretory activities is isotiquimide (14). It may be synthesized by metallating (with n-BuLi) 4-methyl-5,6,7,8-tetrahy-droquinoline and condensing this with dimethylmethoxysilylisothiocyanate to produce the desired thioamide isotiquimide (14) [4],... 

Durst and coworkers were the first to report the condensation of chiral a-sulphinyl carbanions with carbonyl compounds477. They found that metallation of ( + )-(S)-benzyl methyl sulphoxide 397 followed by quenching with acetone gives a mixture of dia-stereoisomeric /i-hydroxy sulphoxides 398 in a 15 1 ratio (equation 233). The synthesis of optically active oxiranes was based on this reaction (equation 234). In this context, it is interesting to point out that condensation of benzyl phenyl sulphoxide with benzaldehyde gave a mixture of four / -sulphinyl alcohols (40% overall yield), the ratio of which after immediate work-up was 41 19 8 32478. 

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