958
L I N D A BATTELLE, CAROLYN K N O B L E R , AND
J. L>.
h~CdULLOGG14
lnovganic Chemistry
CONTRIBUTIOX S O . 1974 FROM THE DEPARTMENT O F CHEMISTRY, USIVERSITVo ~ CALIFORNIA i AT L o s AXGELHS, Los ANGELES,CALIFORNIA 90024
The Crystal and Molecular Structure of 1-Thia-4-selenacyclohexane4,4-Dibromide, C,H,SSeBr, BY LIiTDA BATTELLE, CAROLYN KiYOBLER, AND J. D. McCULLOUGH
Received October 20, 1966 1-Thia-4-selenacyclohexane 4,4-dibromide forms yellow crystals belonging to the monoclinic spstcm with u = 11.59 .A, 6 = 6.49 A, c = 12.14 A , and 8 = 112.9'. The space group symmetry is P21/c with four molecules of CaHRSSeBrnin the unit cell. T h e trial structure was refined by use of three-dimensional, full-matrix, least-squares procedures based on 894 uti ique observed reflections. T h e molecular symmetry approximates m with the six-membered ring in the chair form. The bonding about selenium approximates a trigonal bipyramid with bromine atoms in the axial positions, two carbon atoms in equatorial positions, and t h e third equatorial position unoccupied. T h e observed bond distances (in A ) are: Se-Br, 8.545 and 2.548 (csd 0.005); Se-C, 2.01 and 2.02 (esd 0.03); S-C, 1.83 and 1.79 (esd 0.03); and C-C. 1.50 and 1.54 (esd 0.04). T h e more interesting observed bond angles (in degrees) are: Br-Se-Br, 175.1 (esd 0.6); C-Se-C, 105 (esd 2 ) ; and C-S-C, 97 (esd 2 . 5 ) . The plane of the Se-Br bonds is perpendicular to t h a t of the Se-C bonds within the experimental limits of observation. T h e sulfur atom is not involved in bonding except t o two carbon atoms in t h e same ring.
and p = 112.9 =k 0.1'. The density calculated from tliese Introduction parameters is 2.577 g ~ m - based ~ , on four CdHsSSeBrZ per unit Previous attempts to determine the structures of 1cell, while the density observed by flotation is 2.53 g cm-3. thia-4-selenacyclohexane(1,4-thiaselenane) and its The intensity data were taken from multiple-film, integrated, derivatives2, have involved compounds which proved SVeissenberg photographs prepared with Cu K a radiation. As in a number of similar cases involving selenium bromides, to be disordered. The molecules in these cases were copper radiation was found to give photographs superior t o those found to be crystallographically centrosymmetric, a prepared with Mo Ko radiation. Although the absorption errors requirement satisfied by random orientation of the are greater with Cu radiation, the much denser background sulfur and selenium ends of the ring. Thus it would on the Mo photographs (probably caused by fluorescence) caused have been difficult to have obtained good values for other problems. The main set of intensity photographs was taken about the 6 axis Tvith a six-sided prismatic crystal. The bond distances and angles in these compounds. Howcross-sectional dimensions between opposite pairs of faces were ever, a preliminary X-ray diffraction investigation of a 0.12, 0.15, and 0.17 mm, respectively. IVith the average radius number of 1,4-thiaselenane derivatives3 indicated that taken as 0.08 mm, the value of p R for Cu Ko radiation is 1.6. the dibromide did not involve disorder. Its study was Although this is somewhat high, the intensity data were not therefore undertaken, not only because of interest in corrected for absorption. Kumerous unsuccessful attempts were made t o find or prepare a crystal suitable for intensity measthe structure of the ring system, but also to study the urements about the a or c axis for more completeness of data heavy atom bonding in this new environment, the only and for interlayer scaling. Ultimately a set of integrated Weispreviously reported structural studies of organoselenisenberg photographs about [021] was prepared, b u t because of urn dibromides having been on aromatic c o m p o ~ n d s . ~ , ~greater effects of absorption, these photographs werc uscd only
Experimental Section 1-Thia-4-selenacyclohexane was synthesized by the method of McCullough and Lefohn6 and the dibromide prepared as described by M c C ~ l l o u g h . ~Crystals suitable for the X-ray study were grown by slow evaporation of a solution in ethylene chloride. Most specimens showed a prismatic or lath-like development elongated on b , b u t some were polyhedra of roughly equal dimensions. Since there was some tendericy to hydrolyze slowly in air, the specimens used for the intensity measurements were mounted in thin-walled Pyrex capillaries. Weissenberg and precession photographs confirmed the monoclinic diffraction symmetry and the space group, P21/c, found in the preliminary study. The unit cell dimensions were redetermined with the aid of \Yeissenberg and precession photographs prepared with Cu Kcu radiation and calibrated by use of the hk0 reflections of quartz.? On the basis of a = 4.9131 A for quartz, the parameters for 1,4-thiaselenane dibromide were found t o be: u = 11.59 f 0.01 A, b = 6.49 i 0.02 -4, c = 12.14 i 0.01 A, (1) J. D. McCulloughand P. Radlick, Inoig. Chrm., 3, 924 (1964). (2) H. H o p e a n d J. D. McCullough, A c t a Ciyst., 15, 806 (1962). (3) J. D. McCullough,Imi.g. C h ~ m .3, , 1425 (19G4). (4) J. D. McCullough and G. Hamburger, J . A w . Chem. SOC., 63, 803 (1941). ( 6 ) J. D. McCullough and I
