Metallo-de-metallation

For transmetallations with a metal (metallo-de-metallations, Scheme 10-95) arylmercury compounds are particularly suitable due to the position of mercury as a noble metal in the electrochemical series of standard potentials (for examples see Makarova, 1970). 

Transmetallation with a Metal Halide Metallo-de-metallation... 

The literature on metallo-de-hydrogenations of aliphatic diazo compounds is, in contrast to that on substitutions with classical electrophilic reagents, fairly large. It includes the monovalent metals Li, Na, and Ag, the divalent metals Mg, Zn, Cd, and Hg, the trivalent metal Tl, and the tetravalent metals Ge, Sn, and Pb. In addition, substitutions with the hetero atoms B, As, Sb, Bi, and Si, as well as metallo-de-metallations are reported in the literature. Although the synthesis of diethyl mer-cury(bisdiazoacetate) (9.4) was performed quite early (Buchner, 1895), the majority of papers on metallation was published in the 1960 s and 1970 s. ... 

We return now to the mercuro-de-diazoniation. Nesmeyanov s school continued the work on metallo-de-diazoniations from 1929 to 1953 (see summary by Nesmeyanov, 1972). A major discovery was made at the very beginning, namely the influence of copper powder (Nesmeyanov, 1929 b Nesmeyanov and Kahn, 1929). With this addition metallic mercury was not required instead the double salt of the diazonium chloride and mercuric chloride was used. The copper reacts stoichiometrically as an electron donor. Therefore, either arylmercuric chlorides (Scheme 10-87) or diarylmercury compounds (Scheme 10-88) can be obtained. These reactions are called Nesmeyanov reactions. Specific examples are the syntheses of di-2-naphthyl-... 

Metal complex dyes 312 Metallo-de-diazoniations 273 ff. Methanediazonium ion 82, 84, 86, 89, 181 Methoxy-de-diazoniation 162, 198f., 208ff., 212, 277... 

Metallation with Organometallic Compounds Metallation or Metallo-de-hydrogenation... 

Replacement of a Halogen by a Metal from an Organometallic Compound Metallo-de-halogenation... 

Replacement of the Diazonium Group by a Metal Metallo-de-diazoniation... 

Schemes 9-3 and 9-4 are sequences of two substitutions, first a metallo-de-hydrogenation, followed by a halogeno-de-metallation. Scheme 9-3 is analogous to the well known electrophilic aromatic sulfonation of anthraquinone in position 1. This isomer is obtained only if the reaction is run in the presence of catalytic amounts of mercury (ii) salts. Nowadays, however, larger effort is devoted to either replace mercury by other catalysts, or in the search for processes leading to (practically) complete recovery of the mercury. This case raises two questions with respect to the reaction sequence (9-3) first, whether it is possible to apply a one-pot process with catalytic amounts of a mercury compound (not necessarily HgO) to the synthesis of compounds 9.5, and second, whether mercury can be completely recycled in processes using either stoichiometric or catalytic amounts of the element.

The final coordination geometry and stereochemistry of the complex is determined by the particular electronic and steric requirements of the metal atom and its ligands. In addition, interactions of the peptide subunits with each other and with the metal atom are of paramount importance in determining the overall structure of the complex. This makes it possible to create small artificial metallopeptides and metalloproteins with well-defined and stable structural peptide motifs, such as the -sheet structure and helical bundle proteins consisting of helical peptide subunits. Recently a number of de novo metallo-peptide and... 

Dietrich-Buchecker, C.O., Sauvage, JP., and Kitzinger, JP. (1983) Une nouvelle famille de molecules Les metallo-catenanes. Tetrahedron Lett, 24, 5095-5098. Sauvage, J.P. (1990) Interlacing molecular threads on transition metals Catenands, catenates, and knots, Acc. Chem, Res. 23, 319-327. Dietrich-Buchecker, C.O. and Sauvage, JP. (1992) Supramoleculcur chemistry, Kluwer, Amsterdam, 259-277. 

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