Alkaline earth metal chloride-alkoxides

The coordination catalysts for these reactions are diverse. They can be compounds of alkaline earth metals, like calcium amide, or calcium amide-alkoxide. They can also be Ziegler-Natta-type catalysts. These can be alkoxides of aluminum, magnesium, or zinc combined with ferric chloride. Others are reaction products of dialkylzinc with water or alcohol. They can also be bimetallic //-oxoalkoxides, such as [(RO)2A102]Zn. Other catalysts are aluminum or zinc metalloporphyrin derivatives (see Fig. 4.1). 

The strategy of metal alkoxides synthesis is entirely related to the electronegativity of the element concerned. Some electropositive metals, such as alkali metals, alkaline earth metals, and lanthanides, react directly with alcohols. But some less electropositive metals such as magnesium and aluminum require a catalyst (I or HgCy for successful reaction with alcohols. Use of electrochemical synthesis by anodic dissolution of some metals or metalloids (Sc, Y, Ti, Zr, Nb, Ta, Fe, Co, Ni, Cu, Pb, Si, Ge, etc.) in dry alcohol performs a promising procedure because it does not produce any by-products except hydrogen gas. Another applicable method for the synthesis of some alkoxides (B, Si, Ti, Zr, Hf, Nb, Ta, Fe, etc.) is the reaction of their chlorides with alcohols which require a base such as... 

More than two decades after the preparation of a large nnmber of the so-caUed alkoxo salts by Meerwein and Bersin in 1929, U Al(OPr )4 4 was synthesized in 1952 by Albers et al. and evidence for the formation of M U(OEt)6 n (M = Na, Ca, Al) was obtained by Jones et al in 1956. Similarly, formation of a number of anionic methoxide species was indicated in the potentiometric titrations of chlorides of metals (B, Al, Ti, Nb, Ta) with lithium methoxide in methanol by Gut in 1964. Ludman and Waddington studied the conductometric titrations of a wide variety of Lewis acids with basic metal methoxides and reported the formation of alkoxo salts of the type KB(OMe)4 and K3Fe(OMe)e. Schloder and Protzer also synthesized a number of bimetallic alkoxides of aluminium with the formulae, MAl(OMe)4 and M Al(OMe)4 2 where M and M are alkali and alkaline earth metals respectively. 

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