NOTES
July, 1959 chosen for volatility and inertness. The eluate was collected at a rate of 30-40 cc./hr. Separations (Adsorption) .-A petroleum ether solution of 1.0 g. of decaborane and 0.5 g. of biphenyl was chromatographed with petroleum ether as eluent. The initial 600 cc. of eluate contained no solute. Decaborane was eluted over the next 500 cc. of eluate. After 200 cc. of further eluate without solvent, biphenyl was eluted quantitatively. The separations of mixtures of decaborane-benzyldecaborane and decaborane-iododecaborane’ were similar except that in these cases, after the elution of decaborane with petroleum ether, the substituted decaboranes could not be eluted with the latter and methylene chloride was used as the eluent. A petroleum ether extract (8.8 9.) of the benzyl chlorideBloH13MgI reaction6 was chromatographed after distilling the volatile material. This yielded a trace of decaborane, eluted with petroleum ether; this was followed by 2.95 g. of bensyldecaborane, eluted with 25% methylene chloride; the last fraction (1.9 9.) was eluted with methylene chloride and had a cryoscopic molecular weight of 298 and a composition of 72.6% C, 14.7% B and 7.8T0 H. The latter was rechromatographed with gradually increasing concentrations of methylene chloride as eluent but no further separation was noted. Separations (Partition).-A decaborane-biphenyl mixture was chromatographed on a column prepared with diethyl ether, using petroleum ether as eluent. Biphenyl was eluted quantitatively first, followed by decaborane. In a similar manner, a mixture of iododecaborane-di-iododecaborane’ was chromatographed on a column prepared with methylene chloride, using petroleum ether as eluent. Iododecahorane was eluted first, followed by diiododecaborane .a (7) The latter was prepared by an unpublished method. Details were made available to us by a private communication from the Reaction Motors Division, Thiokol Chemical Corp. (8)The melting point of this compound was 268O. Since the diiododecaborane reported by Stock (A. Stock, “Hydrides of Boron and Silicon,” Cornell Univ. Press, Ithaca, N. Y., 1933) melted at 2.30°, the compound isolated in this paper is apparently another isomer.
DISSYMMETRY OF DISCS OF NEGLIGIBLE THICKNESS
1213
0.00
1.00
2.00
d 3.00
4.00
5.00 1.00
0.80
0.60
0.40
0.20
0.00
P(@). Fig. 1.-Scattering
function,
P(q)as
a function of
2.
6.00
5.00
4.00 i
3.00
BY PAULBECHER Chemical Research Dept.. Atlas Powder Cn., Wdmington, Delaware Receiped November 10, 1968
The scattering functions and the corresponding dissymmetry corrections for a variety of molecular shapes, such as spheres, rods and coils, have been tabulated, e.g., by Doty and Steiner.’ Recently, however, we required such information for a discshaped scattering unit. Although no such tabulation apparently exists, Debye2 has shown that the scattering function for a disc of negligible thickness (ie., negligible with respect to the wave length employed) is given by P(8)=
Z”
- x2/6 +
n=m
[x2(‘-l) COS (n
+ l)n]/bn
n=3
where the coefficients b, are given by the recursion formula and where bl = 1 and b2 = 6. The quantity x is defined in the usual maimer x =
2rD
7 sin
x
8
2-
(1) P. Doty and R. F. Steiner, J . Chem. Phvs., 18, 1211 (1950). (2) P. Debye and E. W. Anacker, THISJOURNAL, 55, 644 (1951); Cf. also 0.Kratky snd G. Porod, J . Colloid Sei,, 4, 35 (1948).
2.00
1.00 0.00
0.20
0.40 0.60 0.80 D/Xl. Fig. 2.-Dis~ymmetry, 14j/1135,as a function of D/X’
TABLE I SCATTERING FACTOR FOR THINDISCS z
p (6)
5
0.10 .20 .30 .40 .50 .60 .70 .80 .90 1.00 1.10 1.20 1.30 1.40
0.998 .993 ,985 ,973 .961 ,942 .921 .899 ,874 ,846 ,817 ,787 .756 .722
1.50
,687
2.60 2.70 2.80 2.90 3.00 3.10 3.20 3.30 3.40 3.50 3.60 3.70 3.80 3.90 4.00
P
(8)
0.335 .309 ,286 .263 ,242 .225 ,205 .191 .174 .162 .152 ,143 .132 .124
,116
NOTES
12i4 TABLE I (Continued) 1.60 1.70
1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
,684 .620 .584 .550 .517 .483 ,451 .420 .390 .361
4.10 4.30 4.30 4.40 4.50 4.60 4.70 4.80 4.90 5.00
.113 .lo9 .lo1 .007
cis-trans ISOMERIZATION AND SOLVQLYSIS
,088 .086 .083 .081 .079
OF DICHLQROBIS-(ETHYLENEDIAMINE)CHRQMIUM(II1) CHLORIDE IN NEARLY ANHYDROUS METHAXOLin
5.00
4.00
Is,
=. 3.00
2 .oo
0.40 0.60 0.80 0.90 D/X’. Fig. 3.-Correction function, 1/P(90), as a function of D/x’. 0.20
TABLEI1 AND CORRECTION FACTOR FOR THIN DISCS
DISSYMMETRY (Zo/Z186) D/X’
0.05 .10 .15 .20 .25 .30 .35 .40
.45 .50 .55 .60 .65 .70 .7.5 .80
BY LYNOREE. SLAT EN'^ AND CLIFFORD S. GARNER Department of Chemistry, University of California. Los Angeles 84, California Received November $4, 1968
6.00
1.00 0.00
2 and 3. I t is interesting to note that the behavior of the discs lie between that of a sphere and a rod, a not unexpected result.
.092
6.50
-
5’01. 63
121 1.011 1.047 1.110 1.205 1.338 1.514 1.755 2.075 2.476 3.000 3.641 4.311 4.933 5.682 5.879 6.230
1 / p (W
1.009 1.033 1.078 1.140 1.229 1.342 1.495 1.689 1.934 2.252 2.646 3.145 3.759 4.484 5.376 6.369
where D is the diameter of the disc and A‘ the wave length of light in the medium. The summations involved are straightforward, although tedious, since the series converges slowly. The scattering function is listed as a function of x in Table I, and presented graphically in Fig. 1. The dissymmetry ( [ z ] = 14a/Iras) and the correction function, 1/P(90), are listed as a function of D/X’ in Table 11, and shown graphically in Figs.
Isomerization and substitution reactions of cisC ~ ( e n ) ~ C (en l ~ += ethylenediamine) have been investigated in solvent water and solvent methanoL2 I n aqueous solution the cis-trans isomerization is complicated by competition between chloride ion and water for the cobalt ion. However, in solvent methanol cis- [Co(en)L!l2]CI has been to isomerize quantitatively to the trans-isomer a t 36” by a first-order reaction without net loss of ligand chloride. Trimble6 found no spectrophotometric evidence for any change of the trans-complex in methanol in 12 hours a t 100”. He observed that the cis-complex in 2-methoxyethanol (“Methyl Cellosolve”) isomerizes completely a t 30-50°, followed by a slower reaction between solvent and trans-isomer. Brasted and Hirayama’ studied the isomerization in ethanol and propanol as well as in methanol. Little is known about isomerization of the corresponding chromium(II1) isomers. Trimble6 found that Z-cis-[Cr(en)2C12]C1in 2-methoxyethanol fails to isomerize in 30 minutes a t reflux temperature, although he reported complete racemization in 2 minutes of boiling the solution. We report here a partial kinetic study of the isomerization of cis- [Cr(en)2C12]C1in methanol. We have found that trans- [Cr(en>&l2]C1,unlike the cis- and trans-cobalt analogs, releases ligand chloride a t a measurable rate in nearly anhydrous methanol. Experimental cis-Dichlorobis-(ethylenediamine)-chromium(111) Chloride.-[Cr(en)a] CIS.3 .5H20 was synthesized8 and converted9 which was stored in the dark. to ~is-[Cr(en)~C12]C!l.H~0, Anal. Calcd.: Cr, 17.54; N, 18.89; H20,6.08. Found: 6.08. Water of crystallization Cr, 17.84; N? 18.87; H20, was removed in the dark at ca. 90’ under vacuum just before preparing a reaction mixture. trans-Dichlorobis-( ethylenediamine)-chromium(111) Chloride.-[Cr(en)~](SCN)~.H~O was -~ prepared and convertedg . ~. ~
(1) (a) Supported by U. S. Atomic Energy Commission under Contract AT(ll-1)-34, Project 12; (b) Research Center, International Business Machines Corp., Pooghkeepsie, N . Y . (2) For a general review see F . Basolo and R. G. Pearson, “Mechanisms of Inorganic Reactions,” John Wiley and Sons, Inc., New York, N. Y . , 1958. (3) D. D. Brown, C. K. Ingold and R. S. Nyholm, J . Chem. ~ o c . , 2674 (1953). (4) D. D. Brown and C. K. Ingold, ibid., 2680 (1953). (5) D. D. Brown and R. 9. Nyholm, ibid.. 2096 (1953). (6) R. F. Trirnble, J . A m . Chem. S o c . , 76, 0321 (1954). (7) R. C. Brasted and C. Hirayama, ibid., 80, 788 (1958). (8) J . C. Bailar, Jr., and J. B. Work, ibid.. 67, 176 (1945). (9) C. L. Rollinson and J. C. Bailar, Jr., ibid., 66, 641 (1944); “Inorganic Syntheses,” Vol. 11, W. C. Fernelius, editor, McGraw-Hill Book Co., Inc., New York, N. Y.. 1946, pp. 19G200.
