Metal Oxide Alkoxide Polymers: Part I. The Hydrolysis of Some Primary Alkoxides of Zirconium

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Ebulliometric studies on the hydrolysis of tantalum pentaallcoxides Ta(OR)o, where R = Me, Prn, Bun, and Bu" have furnished important data on the polymeric nature of tantalum oxide allroxides. It is shown from the variation of number-average degrees of polymerization as a function of degree of hydrolysis that the polynlers conform to certain structural models. The structural models involve 6-co-ordinated tantalum.

Section: Figsupporting

confidence: 52%

Metal Oxide Alkoxide Polymers: Part Iv. The Hydrolysis of Some Tantalum Alkoxides

Bradley¹,

Holloway²

1962

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“…Significant variations in a with x,, can thus be masked by a linear plot. The same structural parameters and variation of a with F,, have been proposed previously for these two zirconium oxide alkoxides (3). In general, structural parameters assigned for the other products agree with those asslgned by Bradley and co-workers with a few exceptions.…”

Section: Model IIsupporting

confidence: 87%

“…[2] and [3] and rearrangement gives Inspection of eqs. [ l a ] and [lb] indicates that the molecular weight of chain i will be of the form…”

Section: General Theory For Homogeneous Polymermentioning

confidence: 99%

“…Further, let the relative numbers of repeating units with p = p, be &, and of repeating units withp = p, be 1 -E . Equations [2] and [3] become Table I contains an analysis of all published data on the metal oxide alkoxides (1-7) and the metal oxide trialkylsilyloxides (8-lo), with the exception of the titanium oxide triethylsilyloxides (1 l), which will be discussed elsewhere along with new experimental data (20).…”

Section: General Theory For Heterogeneous Polymermentioning

confidence: 99%

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Structural aspects of the hydrolysis products of metal alkoxides and metal trialkylsilyloxides

Lorimer¹,

Jones²

1969

The average degree of polymerization i?,, depends on the average degree of hydrolysis f,, as I/@, = a + bR,, over a large range of x:, for all metal oxide alkoxides and oxide trialkylsilyloxides that have been formed by hydrolysis and examined in solution. A number of general theoretical models are developed which permit quantitative interpretation of the parameters a and b. Mixtures of linear or branched chains in proportions governed wholly or partly by the degree of polymerization of the unhydrolyzed alkoxide can explain all the data on oxide alkoxides in solution in their corresponding alcohol, and the model leads to a plausible mechanism for disproportionation. Similar models with more complex structure can be involved in the metal oxide trialkylsilyloxides. Heterogeneity in the composition of the repeating units or in the number of metal-oxygen-metal bridges between successive repeating units can also be significant for both oxide alkoxides and oxide trialkylsilyloxides. Models involving cyclic chains are possible, but steric effects make them improbable in many cases. Mixtures of chains with equal average degrees of hydrolysis for each type of chain have been assumed in previous analyses, but are shown to be special cases of the more general model. IntroductionBradley and co-workers have examined a large number of the polymeric hydrolysis products of metal alkoxides (1-7) and of metal trialkylsilyloxides (8-1 1). Hydrolysis of metal alkoxides gives metal oxide alkoxides, or polyalkylmetalloxanes, e.g.

“…Recent wol-li on the hj.clrolysis of titanium (1,2) and zirconium (3) a1l;oxides has revealed that some of the metal oxide all;oxide polymers conform reasonably well to structural inoclels based on the 6-co-ordi~~ated metal. I n these inorganic ~nacl-omolecules, polymerization is basecl on two fundm~ental processes, namely "condensation" involving 311 .O.>I briclges and co-01-dination involving intermolecular metal-oxj.gen bonds.…”

mentioning

confidence: 99%

Metal Oxide Alkoxide Polymers: Part Ii. The Hydrolysis of Tantalum Pentaethoxide

Bradley¹,

Holloway²

1961

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The hydrolysis of tantalum pentaethoxide has been studied in boiling benzene and in boiling ethanol. Soluble tantalum oxide ethoxides were obtained over a considerable range of hydrolysis. Infrared studies suggest that Ta—OH groups are absent in these products. Ebulliometric studies have shown that the number-average degree of polymerization varies with the degree of hydrolysis in a characteristic manner and this has been quantitatively explained in terms of fundamental structural models based on octahedrally 6-co-ordinated tantalum.