Transition-metal derivatives anions used

Transition metal anions have widely been used in the synthesis of the first row transition metal derivatives of group IV metals however only in one case does the reaction take place with chlorosilanes... 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

Monoanions derived from nitroalkanes are more prone to alkylate on oxygen rather than on carbon in reactions with alkyl halides, as discussed in Section 5.1. Methods to circumvent O-alkylation of nitro compounds are presented in Sections 5.1 and 5.4, in which alkylation of the a.a-dianions of primary nitro compounds and radial reactions are described. Palladium-catalyzed alkylation of nitro compounds offers another useful method for C-alkylation of nitro compounds. Tsuj i and Trost have developed the carbon-carbon bond forming reactions using 7t-allyl Pd complexes. Various nucleophiles such as the anions derived from diethyl malonate or ethyl acetoacetate are employed for this transformation, as shown in Scheme 5.7. This process is now one of the most important tools for synthesis of complex compounds.6811-1 Nitro compounds can participate in palladium-catalyzed alkylation, both as alkylating agents (see Section 7.1.2) and nucleophiles. This section summarizes the C-alkylation of nitro compounds using transition metals. 

Anions derived from transition metal-group IV3 metal bonds may be interesting as potential asymmetric catalysts in phase transfer reactions. This field is developing now and, in general, the use of these complexes as catalysts is at the beginning. 

Germyl metallocene derivatives of the early transition metals, Ti, Zr and Hf (M) have been synthesized by the combination of metallocene halides and germyl anions (equations 4 and 5)38-40. The cyclopentadienyl complexes Cp2M(GePh3)Cl39 are difficult to purify due to their instability in solution however, use of the pentamethylcyclopen-tadienyl group(Cp ) enhances both the solubility and stability of these complexes40,41. 

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