PENTACOORDINATED MOLECULES .93. CONFORMATIONAL VARIATION OF SULFUR-BRIDGED 8-MEMBERED RINGS IN 4-COORDINATED, 5-COORDINATED, AND 6-COORDINATED OXYGEN-LIGATED PHOSPHORUS-COMPOUNDS

Reaction of the eight-membered sulfur-containing cyclic phosphine, [(t-Bu)4C12H4SO2]POCH2CF3 (1) with phenols yielded the phosphate [(t-Bu)4Cl2H4SO2]P(O)OCH2CF3 (2) and the pentaoxyphosphorane [(t-Bu)4C12H4SO2]P(C12H8O2)OCH2CF3 Two crystalline modifications of 2 were obtained, an anti (2a) and a syn (2s) form. Due to P-S bond formation, 3 resulted as a pseudooctahedral structure. The conformation of the eight-membered ring varied in all three structures. When compared with related structures containing this basic ring system, a high degree of conformational flexibility is apparent with coordination geometries at phosphorus extending from 4 to 6. Achievement of diequatorial ring orientation in trigonal bipyramids observed for some pentaoxyphosphoranes containing eight-membered rings and the lack of this orientation with six- and seven-membered rings in analogous structures is attributed to the greater conformational flexibility of the eight-membered rings, particularly their ability to maximize ring P-O(eq) pi-bonding. Phosphate 2a crystallizes in the monoclinic space group P2(1)/c with a = 9.608 (3) angstrom, b = 16.085 (6) angstrom, c = 22.772 (3) angstrom, beta = 100.57 (2)-degrees, and Z = 4. Phosphate 2s crystallizes in the triclinic space group P1BAR with a = 9.517 (3) angstrom, b = 13.229 (3) angstrom, c = 13.244 (3) angstrom, alpha = 83.20 (2)-degrees, beta = 78.52 (2)-degrees, gamma = 77.56 (2)-degrees, and Z = 2. Phosphorane 3 crystallizes in the orthorhombic space group Pbca with a = 16.186 (5) angstrom, b = 18.701 (5) angstrom, c = 27.113 (7) angstrom, and Z = 8. The final conventional unweighted residuals are 0.062 (2a), 0.041 (2s), and 0.078 (3).