6521
Dec. 20, 1955
NOTES
The best procedure for purifying a cobalt salt is thus to start with cobalt nitrate, extract a solution 0.35 M in cobalt and 5 M in N H S C N with hexone a t l o , wash this once with 5 M NH4SCN a t 1" and evaporate the organic phase to dryness over &Sob. With quantitative recovery of the organic phases, this procedure will yield more than 99.5% of the original cobalt with the nickel impurity reduced by a factor of lo4. Recycling will give higher purifications. The thiocyanate-hexone extraction has also been used in this Laboratory for the separation of carrier-free Nib' tracer from proton-bombarded cobalt. Very high specific activity can be obtained if the cobalt target is first purified of nickel as described above.
Anal. Calcd. for Pd(C4H$3z)Cl2: C, 16.02; H, 3.36; C1, 23.65. Found: C, 16.13; H , 3.53; C1, 23.54. Dichloro-( 1,Z-dimethyhercaptoethane)-copper (11).This compound was prepared according to the directions of Morgan and L e d b ~ r y . ~ The dark green product was recrystallized from hot alcohol as fine needles. Anal. Calcd. for Cu(C4HloS2)C12: C, 18.71; H , 3.93; C1,27.63. Found: C, 18.76; H , 3.92; C1, 27.68. Dichloro-( 1,2-dirnethylmercaptoethane)-mercury (II).-This compound w3s prepared according to the directions of Morgan and L e d b ~ r y . The ~ white crystalline powder was recrystallized from hot alcohol in the form of white needles. Anal. Calcd. for Hg(CdHloS2)Cl?: C, 12.20; H , 2.56; C1, 18.01. Found: C, 12.48; H,2.76; C1, 18.41. Diiodo-(dimethy1mercaptoethane)-cadmium (11).-This compound was prepared according to the directions of Morgan and L e d b ~ r y . The ~ white product recrystallized from hot alcohol in the form of colorless prisms. Anal. Calcd. for Cd(C4H&)12: C, 9.85; H, 2.06; I, 51.96. Found: C, 10.15; H , 2.28; I, 52.39. Bis-( 1,Z-dimethy1mercaptoethane)-nickel(11) Thiocyanate.-This compound was prepared according to the directions of Tschugaeff .6 Anal. Calcd. for [~i(C4HlaS2)2](SCii)~: C, 28.57; H , 4.80; S , 6 . 6 7 . Found: C,28.72; H,4.94; N, 6.77. Apparatus and Procedure.-All spectra were obtained by means of Perkin-Elmer model 21 recording infrared spectrophotometer, employing a NaCl prism. The liquid and solid state spectra of 1,2-dimethylmercaptoethane were obtained from thin films of the compound contained in a low temperature cell similar to that described by Wagner and H ~ r n i n g . ~ The spectra of the solid complexes were obtained by means of the KBr disk technique* and checked by measurements in nujol mulls.
MALLINCKRODT LABORATORY HARVARD UNIVERSITY CAMBRIDGE, MASS.
Infrared Absorption Spectra of Inorganic Coordination Complexes. VI. The Molecular Structure of 1,2-Dimethylmercaptoethaneand its Metal Chelate Compounds1 BY D. M. S W E E S Y ,SAN-ICHIRO ~~ MIZUSHIMA~~ ASD J. X7. QUAGLIANO RECEIVED JULY 27, 1955
1,2-Dimethylmercaptoethane, H ~ C S C H ~ C H Z Experimental Results SCH3, has several axes of internal rotation and, therefore, may exist in several molecular forms in The infrared frequencies of both the liquid and the liquid state.3 However, this molecule cannot the solid states of 1,2-dimethylmercaptoethaneare exist in the extended form as a chelate ligand in co- shown in Table I. ordination compounds. Therefore, marked difTABLE I" ferences in the absorption spectra are to be expected I S F R A R E D FREQUENCIES I N CM.-' O F 1,Z-DIMETHYLMERfor the free organic compound and for the ligand in CAPTOETHANE its metal complexes. Solid state Liqiiid state Solid stale Liquid state This study was carried out to investigate spec2910 s 2925 s .. 1010 m sh tral differences between the free molecule and the 2350 vw 964 vs 958 vs 2300 vw molecule coordinated about a metal ion in order to 2010 v w 1970 vw .. 900 w contribute to the knowledge of the geometrical role 1430 vs 1430 vs .. 840 m of chelated ligands, having internal rotation axes, 1323 m 735 vs 736 vs 1320 m in metal complexes. .. 1270 s 728 vs sh .. Experimental Preparation of Compounds. 1,2-Dimethylmercaptoethane.-This compound was prepared according to the method of Morgan and led bur^.^ The product was a colorless liquid boiling a t 181°, a t atmospheric pressure. Anal. Calcd. for CdH1OSP: S, 52.46; C, 39.29; H , 8.24. Found: S, 52.47; C, 39.11; H , 8.21. Dichloro-( 1,2-dirnethylmercaptoethane)-platinum (11).This compound was prepared according to the method of Tschugaeff ,6 The bright 4 ellow product was recrystallized from hot water. A n d . Calcd. for Pt(C4H1&2)C1~:C, 12.39; € 3 , 2.54; C1,18.25. Found: C, 12.43; H,2.85; C1,18.05. Dichloro-( 1,2-dimethylmercaptoethane)-palladium(11).This compound was prepared according to the directions of Morgan and Ledbury.4 The dark orange product was recrystallized from hot water. (1) For paper I\' in this series see THISJ O U R N A L , 77, 5508 (1935). (2) (a) Abstracted f r o m t h e Ph.D. thesis of Daniel ?VI. Sweeny, Notre Dame, August, 1955. Supported in part under AEC Contract A T (11-1)-38, Radiation Project of t h e University of X'otre Dame. ( b ) Visiting Professor from Faculty (Jf Science, University uf 'l'ukyrl, (3) S. Mizushima, "Structure of Molecules and Internal Rotation," Academic Press, Inc., New York, N. Y . , 1954. (4) G. T. Morgan and W. Ledbury, J Chenz. Soc., 2880 (1'322). ( 5 ) L. Tschugaeff and A. Kobljanski, 2. a i 1 0 ~ 8Chem., . 83,14 (1913).
1210 vs 1203 vs 678 vs 682 vs 1137 s 1136 s Abbreviations: s = strong; m = medium; w = weak; v = very; sh = shoulder.
The infrared frequencies of metal complexes containing 1,2-dimethylmercaptoethaneas a ligand are shown in Table 11. Discussion of Results
X comparison of the spectra of 1,2-dimethylmercaptoethane in the liquid state with the solid state shows that the former has more absorption peaks. The number of peaks observed in the spectrum of the ligand in the solid state are not so numerous as to be incapable of assignment upon the basis of a single molecular form. This form is probably the extended form.3 ( 6 ) I . . Tschugaeff, Be?., 41, 2222 (1908). ( i )1s:. 1.. Wagner and D. 1'. Homing, J . Cliciii. Piiys., 18, 2!fG (1930). (8) M. RI. Stimson and M. J . O'Donnell, THISJOURNAL, 74, 180.5 (1052); see also J. P. F a u s t and J. V. Quagliano, ibid., 76, 5346 (19.54).
652%
Vol. 77
NOTES
previous communicationg we can definitely conclude that in the liquid state of 1,2-dimethylmercaptoethane some molecules are in the gauche form, since the H2C-CH2 segment of the molecule is in the (DSIE)(DME)(DME)(DME)( D M E ) - (D>lE)tXigauche configuration. PtC!z PdClz CuC1zC HgClzd CdIta (SCN)d The presence of the trans CH2 rocking vibration 2950 w 2930 w 2900 vw 2910 vw ..... 2900 w of the extended form of the free ligand is indicated .... ..... ..... ..... 2085vs ..... by the peak a t 736 cm.-' which is observed for both 14451x1 1440 s 1440m 1422111 1425 s 1425 s the liquid and solid states, in perfect agreement with 1420 s 1415 s 1425 s 1405 m 1410 s . . . expectations. The peak a t 736 cm.-' disappears 1305111 1320 s 1320 m 1330 vw ..... 1324 12' completely in the spectra of these metal chelate .. ..... ..... 1280 vw . . . . ..... complexes and i t can be concluded with certainty .... 1258 s 1258 m 1264 vw 1260 s 1265 w that the ligand in the complex is not present in the . . . ..... 1177 w 1180 vw 1182 12' 1182 w extended form. The presence of the two CH2rock1130 w 1145s 1146 w 1160vw 1 1 2 7 ~ 1125 w ing peaks a t approximately 900 and 545 ern.-', 1028m 1036s 1021 s 1034s 1 0 2 4 ~ 1025vw shows that the form actually present should be a 972 s 977 vs ..... 980 s 973 s 970 s gauche form. 964 s 962 sh 970 s 966 s 962 s 955 sh With regard to the frequency region just consid915m 913 IV 903 m 885 s 890 w 892 TV ered, all the experimental data are consistent with 852 s 849 shb 845 s 829 s 826 VIV 849 m the conclusions that (1) the solid state of the 1,2.... 838 m 840 s ..... ..... ... dimethylmercaptoethane consists of only the exDME = 1,2-dimethylmercaptoethane; all other ab- tended form of the molecule; (2) the liquid state I n some cases we observed breviations same as Table I. consists of both extended and gauche forms of the another peak quite close to one of the CH2 rocking vibration molecule; ( 3 ) the chelated ligand is present only in bands which may be assigned to a n overtone, combination Other peaks a t 732 w; the gauche form. This bears an important relatone, etc. Other peak a t 650 s. 706 w. e Other peak at 713 w. I Other peaks a t 805 s; tion to the optical isomerism of a new type described 658 w. in a previous communication.'O Although the spectrum of the ligand in the liquid In other spectral regions not thus far discussed, state contains all the peaks present in the spec- changes in spectra were observed on transitions betrum of the solid state, there are, in addition, other tween the liquid state, solid state and metal compeaks which indicate the presence of one or more plexes containing the ligand. Three definite difmolecular forms other than the extended form. ferences in spectra were observed on transition from I t is important to realize, however, that some of the the solid to the liquid state, namely, the disappearabsorption peaks assigned to the extended form ance of an absorption peak a t 728 cm.-', and the may overlap those of other molecular forms present appearance of two absorption peaks a t 1010 and in the liquid state. Taking this into account, the 1272 cm.-l. These latter peaks a t 1010 and 1272 spectra observed for the various metal complexes cm.-' undoubtedly can be assigned to the gauche investigated can be explained as arising from the vi- form of the molecule. Their modes are probably brations of the ligand in some configuration other C-C stretching and CH2 wagging, respectively. than the extended form. We do not observe in the The peak a t 728 ern.-' can probably be assigned to spectra of these metal complexes any absorption one of the C-S stretching frequencies. The absence peaks characteristic only of the extended form of of this peak in the spectrum of the liquid state of the ligand. Therefore, i t is reasonable to conclude 1,2-dimethylmercaptoethanemay be attributed to that the ligand is not present in its extended form. its being overlapped by the peak a t 736 cm.-' To facilitate the understanding of our interpre- which is assigned to the trans CH2 rocking vibratations of the spectra, assignments of the peaks ob- tion. served in the region extending from 740 to 950 cm. -' There are, however, many peaks present in the are first presented. In a previous paperg it was spectra which show no essential difference upon shown that this part of the spectrum is the region the transition from the solid state to the liquid state. characteristic of the CH2 rocking frequencies asso- The most intense of these absorption peaks appear ciated with the molecular type XH2C-CHzX. If a t about 1430 and 960 cm.-*. These peaks can be the ligand part of the metal complexes is present in assigned, respectively, to the CH3 degenerate defthe extended form, then the appearance of only one ormation together with the CH2 bending deformaabsorption peak a t about '740 cm.-' is expected, but tion, and the CH3 rocking vibration." I t will be not the appearance of two absorption peaks, cor- seen readily from Table I1 that the absorption specresponding to the CH2 rocking frequencies of the trum of the copper(I1) complex contains only those gauche form.g Since, in the solid state of 1,2-di- peaks which can be assigned to the gauche form. methylmercaptoethane, only one absorption peak 'The other coordination compounds can be treated a t 735 cm.-' is observed in this region, i t is quite in an analogous manner, although some differences reasonable to conclude that the extended form of in spectra exist which do not essentially affect the the molecule is present. However, the spectrum above conclusions. of the ligand itself in the liquid state reveals the I~EPARTXEXT OF CHEMISTRY presence of two absorption peaks a t 900 and 840 YNIVERSITYOF KOTREDAME DAME,ISDIANA cm.-'. Therefore, on the basis of the results of our NOTRE ~. -_ ~ _ _ TABLE 11" INFRARED FREQUENCIES IN CM.--I OF METALCOORDISATION COMPOUNDS C O N T A I N I N G 1,Z-DIMETHYLMERCAPTOETHANE AS A CHELATE GROUP
( P i S. Mizushima, 1. Nakagawa. I. Ichishima and J 1'. Quaglianu. J . P h y s . Chem, 69, 293 (19;:); see also S. M i z u s h i m a , I . S a k a g a w a , I . Ichishima and T. Miyazawa, J . Chcrrz. f h y s . , 2 2 , I b l 1 t l < l , j 4 ) .
(10) J .
V. Quagliano a n d S. Mizushima, THISJ U U K N A I , . 76, IN84
( l!l.i:3).
(11) I . Xakagawa and S. Mizushima, t u bc published.
