Organometallic alkoxides

Since a discussion of the properties and structures of metal alkoxides is essential for an understanding of the chemical processes during hydrolytic polycondensation, a short introduction to the chemistry of metal alkoxides is given first. This overview is restricted to the alkoxides of the network forming elements relevant to sol-gel processing (i.e., alkali and alkaline earth alkoxides, organometallic alkoxides, or alkoxides with metal-metal multiple bonds are not treated) excluding silicon. Three comprehensive books on metal alkoxides have appeared. ... 

The discussion in this chapter, on one hand, exclude organometallic alkoxides as in these compounds the alkoxo groups may play a minor role in determining the properties of the molecule [1]. On the other hand, the discussion generally focuses on literature reports after the 2000. 

Interest in the chemistry of organometallic alkoxides, and particularly aryloxides, has been continued from last year. Ethanolysis of Me2Al(OEt) does not give pure A1(OEt)3, instead... 

The further study on sol-gel preparation of MEEP-silicate composite materials involved the synthesis of a polyphosphazene precursor via the covalent linkage of MEEP with an organometallic alkoxide (triethoxysilane group) [63]. The following hydrolysis and condensation produced a covalently interconnected hybrid material with controlled morphologies and physical properties. A maximum ionic conductivity of 7.69 X10 S cm was achieved for the composite materials complexed with LiTFSI salt. 

Zirconium tetrachloride is instantly hydrolyzed in water to zirconium oxide dichloride octahydrate [13520-92-8]. Zirconium tetrachloride exchanges chlorine for 0x0 bonds in the reaction with hydroxylic ligands, forming alkoxides from alcohols (see Alkoxides, METAl). Zirconium tetrachloride combines with many Lewis bases such as dimethyl sulfoxide, phosphoms oxychloride and amines including ammonia, ethers, and ketones. The zirconium organometalLic compounds ate all derived from zirconium tetrachloride. 

In recent years this simple picture has been completely transformed and it is now recognized that the alkali metals have a rich and extremely varied coordination chemistry which frequently transcends even that of the transition metals. The efflorescence is due to several factors such as the emerging molecular chemistry of lithium in particular, the imaginative use of bulky ligands, the burgeoning numbers of metal amides, alkoxides, enolates and organometallic compounds, and the exploitation of multidentate... 

Reaction with halides or alkoxides of elements less electropositive than A1 affords a useful route to other organometallics ... 

The Peterson olefination is a quite modern method in organic synthesis its mechanism is still not completely understood. " The a-silyl organometallic reagent 2 reacts with the carbonyl substrate 1 by formation of a carbon-carbon single bond to give the diastereomeric alkoxides 4a and 4b upon hydrolysis the latter are converted into /3-hydroxysilanes 5a and 5b ... 

The anionic Rh(I) porphyrin [Rh(OEP) induced ring-opening reactions with 4- and 5-membered ring lactones to give organometallic products with the rhodium bonded to the alkoxide carbon rather than the carbonyl carbon. 

Another variant of the above-mentioned routes to silenes involved treatment of the carbinols (Me3Si)3SiC(OH)RR, formed from the addition of organometallic reagents R Li to polysilylacylsilanes, with bases such as NaH64 or MeLi,57,64 leading to the formation of alkoxides. These alkoxides spontaneously lost trimethylsilanolate ion, yielding silenes references for these reactions are listed in Table I. 

The ring strain inherent in species XV increases its propensity for polymerization. A substantial number of organo-halogenocyclophosphazenes have now been polymerized (7-17). After polymerization, the halogen atoms can be replaced by treatment with alkoxides, aryloxides, primary or secondary amines, or organometallic reagents. 

In some examples it is not necessary to prepare the organometallic-coupling agent R2MX2 beforehand. Thus coating glass fibres with a heptane or alcohol solution of titanium alkoxide promotes adhesion between the fibre and polymer, e.g., acrylic, polyolefins, polyester, polyamide and other thermoplastic resins. 

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