Metal chloride alkoxides

From Metal Halides. The reaction of metal chlorides with alcohols can give metal chloride alkoxides (67—69), eg... 

Mixed Halide Alkoxides. Metal chlorides, hydrogen chloride, and carboxyUc acid chlorides convert metal alkoxides to metal chloride alkoxides. 

Mixed chloiide alkoxides aie prepared by reaction with acyl chlorides, metal chlorides, hydrogen chloride, or chlorine (64). 

Our preliminary attempts to obtain a basic chiral rare earth complex have led us to create several new chiral heterobimetallic complexes which catalyze various types of asymmetric reactions. The rare earth-alkali metal-tris(l,f-bi-2-naphthoxide) complexes (LnMB, where Ln = rare earth, M = alkali metal, and B = l,l -bi-2-naphthoxide) have been efficiently synthesized from the corresponding metal chloride and/or alkoxide,13,41 and the structures of the LnMB complexes have been unequivocally... 

The metathesis reaction of metal chloride with alkali alkoxides (method 5) was historically the first approach applied, and it remains the main route to both mono- and bimetallic derivatives of Mn(H). The most efficient approach to Mn(II) derivatives is, however, provided by the alcoholysis of the corresponding silylamide (method 4). The derivatives of Mn(IH) and mixed-valence Mn(H,IH) were obtained by alcoholysis ofMn(III) acetate by polyatomic phenols in the presence of 2,2 -dipyridil accompanied by reduction in the latter case (methods 4 and 4+7). 

Higher alkoxides, such as tetra(2-ethylhexyl) titanate, TYZOR TOT [1070-10-6]9 can be prepared by alcohol interchange (transesterification) in a solvent, such as benzene or cyclohexane, to form a volatile azeotrope with the displaced alcohol, or by a solvent-free process involving vacuum removal of the more volatile displaced alcohol. The affinity of an alcohol for titanium decreases in the order primary > secondary > tertiary, and branched > unbranched. Exchange processes are more convenient than direct synthesis of tetraalkoxide from TiCl an alcohol, and a base because a metal chloride need not be handled. However, in general, traces of impurities of mixed tetraalkyl titanates can result. 

The sol-gel process is a wet-chemical technique (chemical solution deposition) widely used recently in the fields of materials science and ceramic engineering. Such methods are used primarily for the fabrication of materials (typically a metal oxide) starting from a chemical solution which acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. Typical precursors are metal alkoxides and metal chlorides, which undergo various forms of hydrolysis and polycondensation reactions. 

Metal alkoxides M(OR), where R is typically an alkyl group (R = Me, Et, etc ), have been known for a long time. Many of them (M = Si, Al, Ti, etc.) are now coimnercially available. They can be synthesized via the reaction of metal chlorides with alcohol as follows ... 

Most transition metal chlorides undergo only partial alcoholysis leading to chloroalkoxides MCl j(OR) j. Therefore the reaction has to be driven to completion by adding a base such as ammonia or sodium alkoxide. 

The reaction of metal chloride with alcohol is not the only way to synthesize alkoxides. Other inorganic compounds such as oxides can also be used as precursors for the synthesis of metal alkoxides ... 

Synthesis of Heteiobimetallic Alkoxides from Metal Chlorides... 

The chlorides of metals with an intermediate electronegativity tend to form chloride alkoxides, but these reactions can be brought to completion in the presence of proton acceptors such as NH3 or alkali metals (K/Na/Li). 

The amide method was found to be convenient and straightforward in many cases. An example is the synthesis of soluble barium terr-butoxide, which has a cubane structure (106b). The preparation of this compound by other routes (e.g, direct action of metals with alcohols or chloride-alkoxide interchange), sometimes tends to be complicated due to the incorporation of chloride or oxide moieties within the structural framework of the final alkoxide product. 

Out of a number of preparative routes described in Section II for preparing metal alkoxides, those involving (a) the metal-carbon bond cleavage reaction (Section II.F), (b) the chloride-alkoxide exchange reaction (Section II.C. 1), (c) the amido-alkoxo exchange reaction (Section II.E), and (d) the alcoholysis reaction (Section II.D) appear to be more convenient and versatile. Schemes 1-6 summarize some of the typical reactions studied for the preparation of metal complexes of alcohol ligands with large steric requirements. 

Scheme 2. Preparation of some di-rerr-buty Imethoxide derivatives of metals via chloride-alkoxide exchange reactions.

Salt elimination between the metal chlorides and an alkali metal alkoxide (Section II.C.l). 

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