Tellurium Tetrachloride
DiscussionAs can be seen in Figure 1, the structure consists of layers of Sb2F7~dimers separated by layers of Cs+ ions. Also shown is the structure as proposed by Bystrom and Wilhelmi. Comparison of the two structures shows the metric relationships between the heavy atoms to be approximately the same, but the fluorine positions are grossly different. Table II shows the distances for cesium coordination. Table II Distances for the Cesium Coordination (A)°C s-F(2) 3.153 Cs-F'(4) 3.208 Cs-F'(2) 3! 247 Cs-F"(4) 3.161Cs-F(4) 3.195 " Least-squares errors are 0.002 A.
The crystal structure of (]~IH4)6MosO27.4HzO has been determined from three-dimensional X-ray diffractometer data and refined to an R index of 6.4 %. The compound was obtained from a concentrated aqueous ammonium heptamolybdate solution after several weeks. It crystallizes in the space group P2~/c with a=9"519, b=11,309, c= 15"049 A, fl= 109"50 °, and Z=2. The structure consists of octamolybdate units which are polymerized to infinite chains through one common oxygen atom. The octamolybdate unit is built up of distorted MoO6 octahedra sharing edges and corners. Mo-O bond lengths vary from 1"697 to 2.401 A, with values of 1.697 to 1"732 A in the terminal bonds. Mo. • • Mo distances are 3"258 to 3.472 A (edge-sharing), 3.778, 3.970 and 3.980 A (corner-sharing). The anion chains are separated by NH + ions and H20 molecules; a probable network of hydrogen bonds is suggested.
I S ck liegenden Si : C-Verhaltnis auch C-C-Gruppierungen auszuschlieljen sind. Dies gilt entsprechend auch fur (3) und (4).Die sechs CH3-Gruppen in (2) lassen sich nach ihrer Stellung unterscheiden: die Methylprotonen an den Si-Atomen 1,9,11 und 13 sowie an 3 und 7 sind symmetrisch aquivalent. Das IH-NMR-Spektrum (220 MHz) besteht aus zwei scharfen SiCHySignalen [r = 9.80 und 9.81), der komplexeren Si2CH2-Signalgruppe (10.06 bis 10.48) und einem Si3CH-Triplett (10.91), deren relative Intensitaten sich wie 12 : 6 : 16 : 2 verhalten. Die weitere Analyse des Spektrums, erganzt durch ein Doppelresonanz-Experiment, sichert die Struktur (2) [31. (3): m/e -520.10496 (ber. fur SigClgH4o+ 520.10534).
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