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R. L. LIVINGSTON AND G. VAUGIIAN
coming with Cr(I1) ion. -3. Diphenylcarbazone reacts with Cr(II1) and Cr(I1) ions to form the same complex as observed above. No reaction occurs with chromium(V1) ion. 3 . The stoichiometry of the reaction of chromium and the reagents is in a ratio of three moles of reagent to two nioles of the metallic ion. 4. The highly absorbing chroniium coniplex exists as a cationic species in aqueous solution. 5. The chromium complex is extracted, together with an anion, into non-aque-
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6 . X chromiuin(111)-diphenylcarbazone complex is postulated as the colored species in the reactions. The above conclusions are the result of all of the experimental data obtained. This situation is unique in studies of the systems under consideration. Such a situation serves to clarify much of the unsatisfactory nature of the existing literature on the subject. ous media as a neutral nlolecule.
IOWA CITY.IOWA
[CONTRIBUTION FROM THE DEPARTMENT O F CHEMISTRY AND THE PURDUE
RESEARCH FOUSDATION, PURDUE
UNIVERSITY]
The Molecular Structure of Perfluorotrimethylamine by Electron Diffraction1 BY R. L. LIVINGSTON AND G. VAUGHAN RECEIVED MARCH15, 1956 The molecular structure of perfluorotrimethylamine has been investigated by electron diffraction using the visual coi-rclation procedure. T h e $ r u c t u r a l parameters, as determined by this investigation, are as follows: C-F = 1.32 f 0.0% .&., C-N = 1.43 =t0.03A., L F C F = 108.5 =I=2.0", and LCNC = 114 & 3".
Introduction diffraction features on three of the best plates are Previous investigations of the structures of summarized in Table I. These values are based on hexafluoropropene2 and octafluorocyclobutane3~4 measurements of each feature by two observers. in this Laboratory indicated, for these molecules, The visual curve shown in Fig. 1 was based on inthat the closest approach of fluorine atoms which dependent interpretations of the patterns by three are bonded to different carbon atoms is about 2.70 observers. The interpretations were in close agreeA. or twice the van der Kaals radius of fluorine. ment on all features except as noted below in the Preliminary calculations on perfluorotrimethyl- case of the eighth maximum and the ninth minimum. amine indicated that if a similar F..F distance pre- The portion of the curve in the interval q = 0 to vailed in this compound, then rather unusual struc- p = 20 was copied directly from the most accepttural parameters would be encountered ; hence an able model as is customary. Due to the diffuse nature of the eighth maximum investigation of the molecular parameters of this and the ninth minimum, there was some doubt as compound was undertaken. to the exact shape of these features. However, it Experimental was the opinion of all observers that the maxiinuin The sample of perfluorotrirnethylarnine was supplied by was asymmetric to the outside and that the inDr. W. H. Pearlson of the Minnesota Mining and Manu- dicated shapes of these features are approximately facturing Company. In the absence of any comparative data, their estimate of a purity greater than 98 niol per cent. correct. Due consideration was given to this miwas based on the constancy of the boiling point and the certainty in selecting acceptable models. molecular weight over successive distillations. No known The radical distribution curve appearing in Fig. compounds were observed as impurities in the infrared 1 was calculated using the equation8 spectrum. T h e diffraction photographs were obtained in the usual way6 using a camera designed and constructed by Professor H . J. Yearian of the Purdue Physics Department. The camera distance was about 107.1 mm., and the electron wave length, as determined from a transmission pattern of ZtiO, was about 0.05SS a. T h e recorded diffraction pattern of pcrfluorotriinetliylaInine extended t o a q value of about 95.
Interpretation of the Diffraction Pattern.-The visual correlation n i e t h ~ d ~and . ~ the radial distribution i n e t h ~ dwere ~ , ~used in interpretation of the diffraction pattern. The measurements of the (1) Contains material from the P h . D . thesis of G. Vaughan, Purdue Research Foundation Fellow in Chemistry, 1951-1953. ( 2 ) F. A. M. Buck and R. L. Livingston, J . Chem. P h y s . , 18, 570 (1950). (3) IT. P. Lemaire and I
