Chemical reactivity heterometallics

The chemical reactivity of the C=CH portion of terminal 1,3-diynyl ligands is often found to resemble that of conventional organic 1-alkynes.36 Consequently, numerous examples of heterometallic diyndiyl complexes have been prepared (Table VI). The most frequently used methods involve metallation of terminal diynyl complexes MLX C=CC=CH, usually with similar synthetic protocols to those described for the preparation of diynyl and homometallic diyndiyls. General methods include ... 

Most ceramics and glasses are based on silica. The problem then is to form Si-O-M bonds in the molecular precursor and to keep them during the whole hydrolysis and condensation processes. However, silicon has a rather high electronegativity (XSi=L74) and does not show any tendency toward coordination expansion. Its chemical reactivity toward hydrolysis and condensation is therefore quite low. Silicon alkoxides Si(OR)4 always exhibit a monomeric tetrahedral molecular structure and very few heterometallic alkoxides or oxo-alkoxides are formed with silicon (4). It is therefore difficult to prepare homogeneous multicomponent gels in silicate systems... 

Caulton, K.G and Hubert-Pfalzgraf, L.G. (1990) Synthesis structural principles and reactivity of heterometallic alkoxides. Chemical Reviews, 90, 969-995. 

There is a considerable interest in heterometallic molecular clusters containing gold. This includes the development of methods of synthesis, the study of their bonding, and their chemical and catalytic reactivities. Furthermore, metal-metal bonded compounds of gold represent an important aspect to the chemistry of this element. 

The chemistry of bis(alkynyl) metal complexes, including the titanium derivatives, focusing on the synthesis, chemical behavior, structure, and bonding of different type of mononuclear and heterometallic molecules has been discussed in a review.1280 A review focusing the preparation and the reactivity of compounds of the type Cp 2Ti-(ct-C=CR)2 (Cp = Cp, Gp ) has appeared which summarizes special aspects of C-C coupling and cleavage processes in organic reactions.1281... 

This chapter deals with the synthesis and general properties of homo- and heterometallic alkoxides that are or might be used in chemical routes to electrooptical ceramic materials. Some considerations concerning structure, reactivity, and tailoring of their properties are also given. Emphasis is given to the most recent results. 

The chemical properties of heterometallic alkoxides are in general similar to their homometal counterparts (i) hydrolysis, (ii) alcoholysis, (iii) trans-esterification reactions, (iv) reactivity with carboxylic acids and enolic forms of chelating ligands such as /3-diketones/j6-ketoesters. The hydrolytic reactions are now widely employed for the preparation of homogeneous mixed metal-oxide ceramic materials and the rest have found wide applications for the synthesis of a variety of novel metallo-organic derivatives (sometimes unique), which are not often available through any other synthetic route. ... 

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