STRUCTURES OF THE TRANS AND CIS ISOMERS OF 5-DIOXO-3,5-DIISOPROPOXY-1,3,5-THIADIPHOSPHORINANE

Both isomers of 5-dioxo-3,5-diisopropoxy-1,3,5-thiadiphosphorinane hav e two molecules in the asymmetric unit. The trans isomer crystallises in P1BAR with a = 9.635 (3) angstrom, b = 10.516 (3) angstrom, c = 14. 146 (4) angstrom, alpha = 93.20(2), angstrom beta = 100.28 (2) angstro m, gamma = 90.18(2)-degrees (at 178 K), final R(F) 0.041. The cis isom er crystallises in P2(1)/n with a = 8.459(4) angstrom, b = 11.410(4), angstrom c = 29.458(12) angstrom, beta = 93.12(3)-degrees (at 293 K), final R(F) 0.046. The rings adopt a chair conformation. All four rings display closely similar dimensions. The P-C-P angles are wide (120-de grees). In the cis isomer the bulky substituents are both axial, where as in the trans isomer one substituent is forced to be equatorial.