MAXT . ROGERS AND ROBERT A. SPURR
2102 [CONTRIBUTION FROM THE
GATESAND
CRELLIN
LABORATORIES O F CHENISTRY, No. 11081
VOl. 69
CALIFORNIA INSTITUTE O F
TECHNOLOGY,
The Structure of Tellurium Dibromide BY MAXT. ROGERS~ AND ROBERT A. Spumy
An electron diffraction investigation of telOne would expect for these compounds bonds lurium dihalides was made by Grether,: who re- with some s character, giving angles between 90 ported the values Te-C1 = 2.36 * 0.03A., Te-Br and llOo, as observed for sulfur dichloride = 2.49 f 0.03 A,, L Br-Te-Br and L CI--Te-Cl ( L C1-S-C1 = lolo),' and for elementary selenium 2 150'. The extensive absorption bands of these and tellurium in the crystal (LTe-Te-Te = compounds have been investigated by L a r i ~ n o v , ~102'). Since the above experiments indicate a and by Wehrli5; the former considered that the much wider angle (150-180°), i t was c'onsidered angles were similar to the angle (115 * 4') found6 desirable to reinvestigate one of the halides by for chlorine monoxide while the latter author re- the electron diffraction method. Tellurium diported that tellurium dichloride is nearly linear bromide was chosen because i t is stable in the in the ground and first excited states. Neither vapor state a t the boiling pointS and offers the spectroscopic investigation is conclusive, however, most favorable ratio of scattering factors for detersince i t has not been possible to obtain a complete mining the angle. analysis of these complicated spectra. Experimental Tellurium dibromide was prepared by treating .A powdered C.P. tellurium metal with C.P. bromine 0 1 3 3 4 8 in equivalent amount; the product was distilled I l l / / , in vacuo and purified by subliming in vacuo. The wave length of the electrons was determinedoby calibration against gold foil (ao = 4.070 A.). Photographs taken a t temperatures up to the boiling point, using the high temperature n o ~ z l e , ~ showed maxima out to q = 66. Interpretation The radial distribution curve (R of Fig. 1) was calculated using the formula r ~ ( r= )
ck sin ( ~ r q k / l ~ )
k c k = I k ( q d exp
(-4)
where Ik(i&) is a visually estimated intensity asTABLE I Min. Max.
1 2
2 0 20 40 60 Fig. 1.-Electron diffraction curves for tellurium dibromide:
