INDIAN J. CHEM., VOL. 19A, OCTOBER 1980

2. NATARAJAN, R. & VENKATASUBRAMANIAN,N., Tetrahedron,30 (1974), 2785.

3. NATARAJAN, R. & VENKATASUBRAMANIAN, N., Indian J.Chem., 17A (1979), 257.

4. VUAYALAKSHMI& SUNDARAM, E. V., J. Indian chem. Soc.,55 (1978), 567.

5. VIJAYALAKSHMI & SUNDARAM, E. V., Indian J. Chem.,15A (1977), 612.

6. RADHAKRISHNAMURTHI, P. S. & MAHAPATRO, D. K.,lndian J. Chem., 18A (1979), 53.

7. NATARAJAN, R. & VENKATASUERAMANIAN, N., lilt. J.Chern, Kinetics, 8 (1976), 205.

8. AVASTHI & CHATTERJI, A. c., Z. phys, Chem., Leipzig,(1972), 17.

9. BHARGAVA, M., SETHURAM, B. & NAVANEETH RAO, T.,Indian J. Chem., 16A (1978), 651.

Thermal Behaviour of Thallium(I) Halates

M. R. UDUPADepartment of Chemistry, Indian Institute of Technology,

Madras 600 036

Received 9 October 1979; revised 30 January 1980; accepted28 February 1980

The thermal decomposition studies of TIBrO., THO. andTIIO, have been followed by TG. DTA. IR spectroscopy andX-ray powder diffraction methods. TlBrO. decomposes at 473 Kto give TI.Oa and TI Br, and TUO, decomposes to TUO. at 683K. THO. is stable upto 753 K and on decomposition gives TlaO.with the simultaneous volatilization of TU formed.

THERMAL behaviour of thallium(I) chloraterevealed- that it decomposes according to the

reaction, 4TlCIOa ~ 2TlCl+TI20:. + C12+ 9/20t•During the decomposition, a part of the chlorateunderwent disproportionation to perchlorate andchloride as observed=+ in the case of alkali metalchlorates. Simpson et a15• reported that TlBr03decomposes in vacuo to give TL,03' probably throughan intermediate of unknown composition. In thisnote is reported a detailed study on the thermalbehaviour of TlBr03, TIIO~ and TII04 using TG,DT A, IR spectral measurements and X-ray powderdiffraction patterns.

TlBr03, TII03 and TII04 were prepared by theaddition of equal volumes of aqueous solutionscontaining equimolar ratios of thallium/I) nitrateand the corresponding potassium halate. The pre-cipitated thallium(l) halates were recrystallized fromhot water [Found: TI, 62.2, 53.4, 52.1. Calc. forTlBrOa, TII03 and TlIOJ : Ti, 61.5, 53.9, 51.7%respectively]. The IR spectra of rm-o; TlIOa,TlI04 exhibited bands at 760, 750 and 810 em'?respectively which are the respective halogen-oxygenstretching frequencies" due to Br03, lOa and 104groups.

The TG and DT A studies were made in air usinga Stanton recording thermobalance and a Netzschdifferential thermal analyzer respectively. The X-raypowder diffraction patterns were taken with a Debye-Scherrer camera of diam. 0.1146 m, using Cu K.

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radiation. The IR spectra were recorded in KBrin the range 1400-600 ern"! on a Perkin Elmer 257spectrometer. Tl(IlI) was determined iodometri-cally and TI(l) or total thallium in the decompositionresidues was determined by bromine-D MSO method".

The TG curve of TlBr03 (Fig. 1A) indicates thatthere are three distinct stages in the decompositionprocess. The first stage sets in at 473 K with aloss of 24 % of initial weight. The second stagebegins around 673 K and continues upto 863 K,accounting for a total loss of 61 'i~of weight. Thefinal stage of decomposition occurs in the tempera-ture range 963-1073 K. No residue is left behindat 1073 K.

Separate experiments were carried out with 100 mgof TlBrOn, by heating gently with a flame. Whenthe decomposition started, the flame was withdrawnand the sample examined by X-ray and IR measure-ments. The powder patterns showed dllkl values(in A) (4.49w, 3.28s, 3.11s, 2.58w, 2.25m, 1.92m),(3.05s, 2.64m, 1.87w) and (3.9lw, 2.82s, 2.02w) whichcorrespond to TlBr03 (ref. 8), TlBr (ref. 9) and Tl20a(ref. 10) respectively. Further, IR spectrum of thepartially decomposed TIBr03 exhibited a strongband at 760 em'? characteristic of TlBrOa. No otherintermediate product, including TlBr04• is detected.Known amounts of TlBrOa were heated at 473 and863 K separately. The residue at 473 K was foundon X-ray analysis to be a mixture of TlBr and T1203•

On chemical analysis, TIBr and Tl20a contents werefound to be 39.0 and 37.0 % respectively of the initialTlBrOa taken. The decomposition residue at 863 Kis found to be only TIPa by X-ray and chemicalanalyses. Separate TG studies on TlBr and Tl203suggest that TlBr volatilizes in the temperaturerange 673-863 K and Tl20a decomposes above 950 K.Thus, the residue at 473 K is T1203 only. Based onthe chemical analysis and the weight loss data, thefollowing decomposition reaction is proposed,

I~O%

A

B

c

300 500 700TEMPERATURE, K

Fig. 1- TG plots of TIBrO. (A), THO. (B) and TIIO. (C)

900 1100

473K7TlBrOa ---+ 2TIPa + 3TlBr + 2Br2+ 15/2 O2

DT A of TlbrO, (Fig. 2A) exhibits an exothermat 473 K due to the decomposition of TlBrOa andan endotherm at 823 K attributed to the volatili-zation of TlBr. Two other endotherms observedat 963 and 1063 K are ascribed! to the decomposi-tion of Tlz03; the former is attributed to the disso-ciation, Tl20a ~ Tl.O + 02' and the latter tothe volatilization of TI20.

The TG plot of TU03 (Fig. 1B) suggests that itlosses 48 % of initial weight in the temperature range753-873 K. Further, weight loss occurs above 963 Kwith no residue at 1063K. The X-ray patterns ofpartially decomposed TUOa showed d"kI values(in A) 3.22s, 3.185, 2.26m, 1.89w, due-! to TU03,

and 3.345, 2.61w, 2.05w, characteristic= of TlI inaddition to those of T1203• The IR spectrum exhi-bited an intense band at 750 crrr? due to TUOa.However, the residue at 873 K is found to be onlyTl20a (51 % by weight). Thus TIl formed duringthe decomposition of TIlOa in the temperaturerange 723-873 K is given out as a volatile product.On the basis of analytical and TG results, the de-composition scheme is given as,

753-873 K7TlIOa ---~ 3TIPs + TIl + 312 + 602

The broad DT A peak (Fig. 2B) at 853 K is ascribedto the combined effect of the decomposition of TU03and the volatilization of TII. The other twoendotherms around 963 and 1063 K are due to thedecomposition of Tlz03•

The TG plot of TlI04 (Fig. IC) indicates threestages in its decomposition process. The first stageoccurring in the temperature range 683-713 Kaccounts for 4 % of weight loss which correspondsto the formation of TlI03 (expected 4.1 %). TheIR and X-ray data of the product at 713 K confirmedit to be TlIOa. The decomposition at higher tem-perature ranges 753-873 K with a weight loss of 51 %and 963-1073 K with no residue, is the characteristic

,£.0

+st,;£ndo

300 500 1100

Fig. 2 - DTA plots of TlBrO. (A), TIIO, (B) and TIIO, (C)

NOT ES

of TIlOa which further supports the formation ofTlIOa during the decomposition of TIlO.!. Theexothermic DT A peak (Fig. 2C) observed at 703 Kis ascribed to the expulsion of oxygen from TlJ04resulting in the formation of TlT03• The endo-thermic peaks around 853 and, 963 and 1063 K aredue to the decomposition of TIl03 and TI~03 res-pectively.

References1. UDUPA, M. R., Thermochim. Acta, 16 (1976), 128.2. MARKOWITZ, M. M., BORYTA, D. A. & STEWART, H.,

J. phys. Chem., 68 (1942), 2282.3. FREEMAN, E. S. & RUDLOff, W. K., Differential thermal

analysis, edited by R. C. Mackenzie (Academic Press,London), 1970, 364.

4. SOLYMOSI, F. & BANSAGI, T., Acta chim. A cad. Sci. Hung.,56 (968), 357.

5. SIMPSON, J., TAYLOR, D., FANSHAWE, R. S., NORBURY,J. M. & WATSON, W. J., J. chem. Soc., (1958), 3323.

6. NAKAMOTO, K., Infrared spectra 0/ inorganic and coordi-nation compounds (Wiley-Interscience, New York), 1969.

7. CHANDRASEKHARAN, M., RAo, V. R. S. & ARAVAMUDAN,G., Talanta, 19 (1972), 383.

8. Powder diffraction file, sets 6-10, edited by L. ,G. Berry(Joint Committee on Powder Diffraction Standards,Pennsylvania), 1967, 293; 8-54.

9. Powder diffraction file, sets 6-10, edited by L. G. Berry(Joint Committee on Powder Diffraction Standards,Pennsylvania), 1967, 405; 8-486.

10. Powder diffraction file, sets 1-5 edited by L. G. Berry (JointCommittee on Powder Diffraction Standards, Pennsyl-vania), 1967, 644; 5-0584.

11. Powder diffraction file, sets 6-10 edited by L. G. Berry(Joint Committee on Powder Diffraction Standards,Pennsylvania), 1967, 288; 8-35.

12. Powder diffraction file, sets 6-10 edited by L. G. Berry(Joint Committee on Powder Diffraction Standards,Pennsylvania), 1967, 37; 6-279.

Studies on Tetrakis(thiourea)nickel(I1) Dichloride &Its Mixed Ligand Complexes

ABU SHAHMA, M. M. KHAN, N. AHMAD· & A. U. MAUK

Department of Chemistry, Aligarh Muslim UniversityAJigarh 202 001

Received 12 November 1979; revised 30 January 1980; accepted19 February 1980

[Ni(tu).]C).. [Ni(tu).py.]C).. [Ni(tuMipyCllCl, [Ni(tu).o-phenCI]C) and [Ni(tu)(PAA)(HPAA)CI] (where tu = thiourea,py = pyridine, dipy=dipyridyl, o-phcn=o-phenanthroline andHPAA=phenylarsonic acid) have been synthesised and charac-terised on the basis of their melting point, elemental analysis,colour, molar conductances, magnetic moment, infra red andelectronic spectral and thermogravimetric data. Ni(tu).C1 isa four-coordinated tetrahedral complex although it has beenreported earlier as octahedral.

THE crystal and molecular structure of Ni(tu)1Clzhas been studied at low temperature by Castro

and Truter! who reported a distorted octahedralarrangement of four thioureas and two chlorides

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