P.N. Kapoor

Organic compounds of niobium and tantalum IV. Reactions of niobium and tantalum pentaethoxides with β-diketones

Abstract The reactions of niobium pentaethoxide with acetylacetone, benzoylacetone and of tantalum pentaethoxide with acetylacetone have been studied and derivatives of the type M(OEt) x (lig) 5− x (where M = Nb or Ta; lig = acetylacetone or benzoylacetone; x = 4, 3 or 2) have been isolated. These derivatives interchange their ethoxy groups with tertiary butoxy groups on refluxing with tert .-butyl alcohol. The molecular weights of β-diketonate as well as β-ketoester derivatives of niobium and tantalum have been determined ebullioscopically in benzene.

Organic compounds of niobium: II. Reactions of niobium penta-ethoxide with β-ketoesters

Abstract The reactions of niobium penta-ethoxide with methyl acetoacetate and ethyl acetoacetate have been carried out in different stoichiometric ratios and the following three types of distillable derivatives (EtO) 4 Nb(lig), (EtO) 3 Nb (lig) 2 and (EtO) 2 Nb(lig) 3 (where lig = either methyl acetoacetate or ethyl acetoacetate) have been isolated in quantitative yields. Further reaction appears to be slow and complicated.

Organic compounds of niobium: V. Reaction of niobium pentaethoxide with glycols

Abstract Reactions of niobium pentaethoxide with diols(ethane, 1,2- and 1,3-propane, 2,3- and 1,4-butane and 1,5-pentane diols, hexylene glycol and pinacol) have been carried out in different stoichiometric ratios and the following three types of new derivatives (EtO) 3 Nb(glycol), (EtO)Nb(glycol) 2 and Nb(glycol) 3 have been isolated. Molecular weights of the few soluble glycollates shows that they are dimeric.

Organic compounds of niobium: I. Reactions of niobium penta-ethoxide with organic esters

The reactions between niobium penta-ethoxide and organic esters (n-propyl, isopropyl, n-butyl, sec.-butyl, tert.-butyl, n-amyl and phenyl acetate) have been studied using the organic esters also as solvent, except in the cases of n-amyl and phenyl acetates, where cyclohexane was used as a solvent. This technique provides a suitable method for the synthesis of niobium penta-tert.-butoxide.

Organic compounds of niobium and tantalum: Alcoholysis reactions of niobium and tantalum penta-alkoxides

Reactions of niobium and tantalum penta-ethoxides with n- and isopropanols, n-, sec.- and tert.-butanols and tert.-pentanol have been studied. In order to make a comparative study of the reactivities of primary, sec.- and tert.-alcohols, the reactions of niobium and tantalum penta-alkoxides (methoxides, ethoxides and isopropoxides) with tert.-butanol, and niobium and tantalum penta-tert.-butoxides with alcohols (methanol, ethanol and isopropanol) have been studied and products of the type M(OBut)(OR)4 (where M is niobium or tantalum) obtained. However, the reactions of penta-methoxides with tert.-butanol yield finally M(OBut)1.5(OMe)3.5. The identity of these mixed alkoxides has been established by distilling or subliming them under reduced pressure. Molecular weights of these mixed alkoxides were determined ebullioscopically in benzene.

Organic compounds of niobium: Reactions of niobium penta-alkoxides with acyl halides

Abstract Compounds Nb(OEt) 4 X, Nb(OEt) 3 X 2 , Nb(OEt) 2 X 3 .CH 3 COOEt and Nb(OEt)Cl 4 .CH 3 COOEt, NbOBr 3 .CH 3 COOEt (where X is chloride or bromide) have been isolated by the reactions of niobium penta-ethoxide with acetyl chloride and bromide. The reactions of niobium penta-isopropoxide and tert. -butoxide with acyl halides in equimolar ratios yield products of the type Nb(OR) 4 X; the products with excess of acyl halides corresponds to NbOX 3 .CH 3 COOR. However, the reaction in the case of penta- tert. -butoxide and acetyl chloride yielded finally NbO(OAc) 0.75 Cl 2.25 · CH 3 COOBu t . The reaction of niobium penta-ethoxide with dry hydrogen chloride gas yielded triethoxide dichloride derivative. Only niobium tetra-alkoxide monochloride derivatives could be distilled or sublimed and these were found to be dimeric in boiling benzene.

Alkali-metal hexa-alkoxides of niobium and of tantalum

Reactions of niobium and tantalum penta-alkoxides with corresponding alkali-metal alkoxides have been studied and a number of double alkoxides of the type MM′(OR)6 have been isolated (M = Li, Na, or K; M′= Nb or Ta; and R = Me, Et, Pri, or But). Tantalum derivatives can be purified by sublimation in a few cases whereas the niobium ones decompose to penta-alkoxides. Conductivities have been measured and molecular weights determined.

Organic compounds of tantalum: I. Reactions of tantalum penta-ethoxide with β-ketoesters

Abstract The reactions between tantalum penta-ethoxide and β-ketoesters lead to the formation of mono-, di-, and tri-substituted derivatives of the type (EtO)4Ta(lig), (EtO)3Ta(lig)2, and (EtO)2Ta(lig)3 (where lig is methyl or ethyl acetoacetate). The first two derivatives interchange their ethoxy groups with tert.-butyl alcohol. The ethoxide and tert.-butoxide derivatives can be purified by distillation or sublimation.

ORGANIC COMPOUNDS OF TANTALUM REACTIONS OF TANTALUM PENTA-ETHOXIDE WITH ORGANIC ESTERS

Reactions of tantalum penta-ethoxide with a number of organic esters, viz.; n-propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, tert.-butyl, n-pentyl and phenyl acetates have been studied and mixed alkoxides of the type Ta(OEt) (OR)4 were obtained except in the cases of sec.-butyl and tert.-butyl acetates which yielded penta-sec.- and tert.-butoxides. All these alkoxides can be purified by distillation or sublimation under reduced pressure. Molecular weights of these mixed alkoxides have been determined ebullioscopically in benzene.

Organic compounds of tantalum: Reactions of tantalum penta-ethoxide with glycols

The reactions between a number of glycols and tantalum penta-ethoxide give, according to the stoichiometric proportions of the reactants employed, tantalum tri-ethoxide mono-glycollate, tantalum mono-ethoxide di-glycollate or tantalum tri-glycollate derivatives. The properties of these compounds are compared with those of the corresponding niobium derivatives. Molecular weight determinations of the soluble compounds show that these glycollate derivatives are dimeric in boiling benzene.