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2 Polish Journal of Chemistry

2 2009

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Synthesis, Characterization and Thermal Studies of Niobium(V) Complexes of 2-tert-Butylphenol

Sharma N., Sharma M., Kumari M., Chaudhry S. C.

Polish Journal of Chemistry

2009

Vol. 83, nr 7

1265-1276

Complexes of composition [NbCl4(OC6H4C(CH3)3-2)] and [NbCl3(OC6H4C(CH3)3-2)2] have been synthesized from the reaction of niobium pentachloride with equimolar and bimolar amounts of 2-tert-butylphenol in carbon tetrachloride. The complexes have been characterized by physicochemical, IR, 1H and 13C NMR and UV-VIS spectral studies. Based upon these studies, for complexes mononuclear square-pyramidal geometry around niobium has been proposed. Thermal decompositional behaviour of the complexes has been studied by TG, DTA and DSC techniques. From TG data, the kinetic and thermodynamic parameters viz. energy of activation, frequency factor, order of reaction, entropy of activation etc. have been evaluated using Freeman-Carroll, Coats-Redfern and Horowitz-Metzger equations. The reactions of complexes with a variety of nitrogenous bases (L1–L5) (where L1 = imidazole, L2 = benzimidazole, L3 = N-methylimidazole, L4 = 2,2'-bipyridyl and L5 = 1,10-phenanthroline) yielded 1:1 addition compounds authenticated by analytical and IR spectral studies.

Synthesis, Characterization and Reactivity of Niobium(V)-2-tert-butylphenoxides

Sharma N., Sharma M., Kumari M., Chaudhry S. C.

Polish Journal of Chemistry

2009

Vol. 83, nr 9

1565-1573

The niobium(V)-2-butylphenoxides of composition [NbCl(OC6H4C(CH3)3-2)4] (I) and [Nb(OC6H4C(CH3)3-2)5] (II) have been synthesized by the reaction of NbCl5 with Me3SiOC6H4C(CH3)3-2 in CCl4 and have been characterized by elemental analyses, molar conductance, molecular weight determination, IR, 1H and 13C NMR and UV-VIS spectral studies. The molecular model calculations were performed to visualize the probable geometry acquired by the complexes. Based upon spectral and molecular modelling dynamics, a square-pyramidal geometry around niobium in complexes has been proposed. Thermal behaviour of the complexes has been studied by TG, DTA and DSC techniques. The reactions of [NbCl(OC6H4C(CH3)3-2)4] (I) with chloride ion accecptors – FeCl3 and PCl5 have yielded complexes of composition [Nb(OC6H4C(CH3)3-2)4]×[FeCl4] and [Nb(OC6H4C(CH3)3-2)4]×[PCl6] authenticated by physicochemical and IR data.