HYPERVALENT PHOSPHORUS-COMPOUNDS WITH SULFUR-CONTAINING 8-MEMBERED RINGS - NATURE OF THE LEAVING GROUP ON HYDROLYSIS TO ACYCLIC VS CYCLIC PHOSPHATES

Reactions of phosphites with diols in the presence of N-chlorodiisopro pylamine in ether solution led to new compounds formulated as the bicy clic tetraoxyphosphorane, [S(Me(2)C(6)H(2)O)(2)](2)PNMe(2) (1), the he xacoordinated pentaoxyphosphorane, S[(t-Bu)(2)C6H2O]P-2(Me(2)C(3)H(4)O (2))(OCH2CF3) (2), with a P-S interaction indicated by P-31 NMR, and t he two phosphates, (CH3CH2CH2)(CH)[t-Bu)(2)C6H2OH](2)}P-2(O)(OCH2CF3) (3) and S(Me(2)C(6)H(2))(2)(OH)OP(O)(OXyl)(2) (4), resulting from hydr olysis reactions. The X-ray structures of 1 and 4 were obtained, and a ll were characterized by NMR spectral measurements in solution. Phosph orane 1 possessed a trigonal bipyramidal geometry displaced 29% toward a rectangular pyramid. The lack of PS coordination, potentially avail able from the two attached eight-membered ring systems, is attributabl e to strong P-N pi bonding. X-ray analysis shows 4 to form as an acycl ic phosphate rather than a cyclic phosphate. This is attributed to the presence of the poor OXyl leaving group. It is proposed that the hydr olysis process leading to acyclic and cyclic phosphates proceeds by wa y of a hexacoordinated intermediate that forms as a result of PS coord ination. Phosphorane 1 crystallizes in the monoclinic space group C2/c with ngstrom,c=24.687(2)Angstrom,beta=131.31(1)degrees, and Z=8. Phos phate 4 crystallizes in the monoclinic space group P2(1)/c with ngstro m,c=10.800(2)Angstrom,beta=109.25(2)degrees, and Z=4. The final conven tional unweighted residuals are 0.059 (1) and 0.035 (4).