Strontium alkoxides

Strontium, aquatetrakis(diacetamide)-structure, 1,98 Strontium, heptaaqua-dodecaiodide structure, 1, 72 Strontium, octaaqua-structure, 1, 84 Strontium alkoxides synthesis, 2,336 Strontium complexes porphyrins, 2, 820 pyridine oxide, 3, 9 Structure... 

The bismuth aUcoxide was insoluble in methoxyethanol because of its own strong association however, it easily dissolved in methoxyethanol containing strontium alkoxide in Sr(OR)2 Bi(OR)3 molar ratios of >0.5 (Katayama and Sekine, 1991). As previously reported, the strong association of the bismuth alkoxide can be destroyed by the formation of a strontium-bismuth double alkoxide. The formation of the strontium-bismuth double alkoxide is discussed next. Also, the bismuth alkoxide was insoluble in strontium-tantalum or strontium-niobium double alkoxide solutions. The strontium-bismuth double alkoxide formed and then reacted with the tantalum or niobium alkoxide to prepare uniform alkoxide complex solutions (Kato et al., 1998). 

Syntheses that exploit the solubility of the alkaline-earth metals in liquid ammonia have proven practical for alkoxide work, as they generate high yields, reaction rates, and purity (Table 8, Equation (3)). In a refinement of this approach, Caulton and co-workers have used dissolved ammonia in an ethereal solvent, usually THF, to effect the production of a number of alkoxides of barium, and this method has also been examined with calcium and strontium (Table 8, Equations (4a) to (4c)). Displacement reactions using alkali metal alkoxides and alkaline-earth dihalides (Table 8, Equation (5)), and between alkaline-earth hydrides or amides and alcohols (Table 8, Equations (6) and (7)), have been examined, but alkali-metal halide impurities, incomplete reactions, and unexpected equilibria and byproducts can affect the usefulness of these approaches. 

Heterometallic alkoxides of calcium, strontium, and barium with transition or posttransition metals have been formed by reactions with the preformed alkoxides (e.g., Table 8, Equations (8a) and (8b)). A variation on this approach generates the Group 2 alkoxides in situ by reaction of the metal with an alcohol and/or another alkoxide (e.g.. Table 8, Equations (9a) and (9b)). " " ... 

Alkaline-earth alkoxides are insoluble and involatile in contrast to the double alkoxides formed by dissolving the alkaline earth metal in a solution of niobium or tantalum isopropoxide in propan-2-ol. With the exception of the magnesium derivative which decomposes on heating, they can be sublimed in vacuo, thermal stability diminishing in the order Ba > Sr > Ca. The calcium and strontium derivatives are monomeric in refluxing benzene, the others are insoluble. Attempts to elucidate structures by n.m.r. spectroscopy were foiled by the rapid exchange of geminal dimethyl protons (see also p. 66). 

Thus, with CsOH as catalyst instead of KOH, PO-based polyethers with very low unsaturation are obtained [18-24, 47, 79, 83-85], the maximum MW possible being 8000 daltons (as compared with a MW of 6500 daltons, which is the maximum MW it is possible to obtain in the presence of KOH). Very low unsaturations are obtained using strontium and barium hydroxides, and alkoxides as catalysts for PO anionic polymerisation [25-29, 79]. 

SBN is a solid solution system containing strontium, barium, and niobium oxides. The sol-gel solution preparation requires special precautions. This is because the alkaline-earth metal alkoxides dissolve in alcohols slowly and they are extremely moisture sensitive. Although alkoxides of both barium and stron-... 

Alkoxides of aluminum, calcium, strontium " and barium " have also been synthesized using iodine as a catalyst. 

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