VARIATIONS IN SULFUR-CONTAINING 8-MEMBERED RING CONFORMATIONS OF HYDROGEN-BONDED AND NON-HYDROGEN-BONDED CYCLIC PHOSPHATES AND OCTAHEDRALLY COORDINATED CYCLIC PENTAOXYPHOSPHORANES

Treatment of tris(2,2,2-trifluoroethyl) phosphite with 2,2'-thiobis(4-methyl-6-tert-butylphenol) led to the monocyclic pentaoxyphosphorane S[(t-Bu)MeC6H2O]2P(OCH2CF3)3 (1), by oxidative addition and to the cyclic phosphates, S[(tert-BU)MeC6H2O]2P(O)OCH2CF3 (2) and S[(t-BU)MeC6H2O]2P(O)OCH2CF3.S[(t-Bu)MeC6H2OH12 (3) by hydrolysis reactions. Each contained the same eight-membered ring with a sulfur atom bridging the aromatic components. X-my analysis of 1 revealed a distorted octahedral geometry due to the presence of sulfur entering the coordination sphere. X-ray analysis showed a ''free cyclic'' phosphate formulation for 2 and a hydrogen bonded form for 3 as a result of the presence of an additional molecule of diol. H-1, F-19, and P-31 solution NMR spectra indicated the presence of non-hydrogen bonded forms for both 2 and 3. The ring conformational variation found for 1-3 and related members indicates that steric properties of ring substituents and the type of bridging group, S and CH2, act as important determinants accounting for the structural changes encountered from trigonal bipyramidal geometries with diequatorial and axial-equatorial ring placements to octahedral forms. Cyclic oxyphosphorane 1 crystallizes in the monoclinic space group P2(1)/n with a = 11.120(2) angstrom, b = 18.179(5) angstrom, c = 17.034(3) angstrom, beta = 104.86(2)., and Z = 4. Cyclic phosphate 2 crystallizes in the monoclinic space group C2/c with a = 28.425(5) angstrom, b = 11.807(2) angstrom, c = 16.434(3) angstrom, beta = 108.89(1)., and Z = 8. Cyclic phosphate 3 crystallizes in the triclinic space group P1BAR with a = 9.180(2) angstrom, b = 10.963(3) angstrom, c = 23.709(6) angstrom, alpha = 81.31(2)., beta = 87.38(2), gamma = 87.71(2)., and Z = 2. The final conventional unweighted residuals are 0.060 (1), 0.040 (2), and 0.072 (3).