Thermoanalytical analysis of Niobium(V) 2-Isopropylphenoxides

ABSTRACT:
The niobium(V) aryloxides of composition [NbCl5-n(OC6H4CH(CH3)2-2)n] (where n = 1→5) has been synthesized by the reactions of niobium pentachloride with 2-isopropylphenol in predetermined molar ratios in carbon tetrachloride and thermal behaviour of newly synthesized Niobium(V) 2-Isopropylphenoxides has been studied by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The results showed that thermal decomposition of complex of composition [NbCl4(OC6H4CH(CH3)2-2)] resulted in the formation of NbOCl3 as the ultimate decompositional product, while [NbCl3(OC6H4CH(CH3)2-2)2] and [NbCl2(OC6H4CH(CH3)2-2)3] complexes yielded NbO(OC6H5)3 and NbO2(OC6H5) as the respective final product of thermal decomposition and [NbCl(OC6H4CH(CH3)2-2)4] has been observed to decompose in two steps. In first step of decomposition corresponds to the formation of NbO2(OC6H5CH(CH3)2-2) as the probable intermediate which has been attributed to the oxidative decomposition of the intermediate to yield Nb2O5. The complex of composition [Nb(OC6H4CH(CH3)2-2)5] has been observed to be least thermally stable. With the help of mathematical analysis of TG data, the kinetic and thermodynamic parameters viz. energy of activation, frequency factor, entropy of activation etc. have been evaluated using Coats-Redfern equation.