83937-47-7Relevant articles and documents
New class of bicyclic oxyphosphoranes with an oxaphosphorinane ring: Molecular structures and activation energies for ligand exchange
Prakasha,Day, Roberta O.,Holmes, Robert R.
, p. 8095 - 8104 (2007/10/02)
Members of a new class of bicyclic oxyphosphorane compounds containing a six-membered oxaphosphorinane ring, Me2C(CH2O)2P(OC12H 8)(OXyl) (1), CH2(MeCHO)2P(OC12H8)(OXyl) (2), and C6H4(CH2O)2P(OC12H 8)-(OXyl) (3), were synthesized in 85-90% yield by the oxidative addition reaction of a diol to the cyclic phosphine precursors. X-ray analysis revealed trigonal bipyramidal (TBP) geometries with the rings spanning axial-equatorial positions. 31P NMR spectral data showed that pentacoordination was retained in solution. Variable-temperature 1H NMR spectra recorded over the range of-90 to 85°C supported intramolecular ligand exchange processes (pseudorotation) where each of the rings was required to be located in diequatorial positions in exchange intermediates. Application of a well-parametrized model treatment, including element effect and ring strain terms, resulted in excellent agreement between calculated and experimental activation energies for ligand exchange in 1-3. Strain energies for diequatorial placement of rings in 1-3 follow the order dibenzo-fused oxaphosphorinane > dioxaphosphorinane > benzo-fused dioxaphosphepane. The results of this study have application to nucleophilic displacement reactions of cyclic phosphorus compounds involving oxyphosphorane intermediates, e.g., cAMP. 1 crystallizes in the triclinic space group P1 with a = 8.607(1) A?, b = 16.817(2) A?, c = 17.153(2) A?, α = 115.15(1)°, β = 90.78(1)°, γ = 91.46(1)°, and Z = 4. 2 crystallizes in the monoclinic space group P21/n with a = 9.315(2) A?, b = 17.422(3) A?, c = 14.096(2) A?, β = 102.04(1)°, and Z = 4. 3 crystallizes in the monoclinic space group P21/c with a = 9.734(1) A?, b = 27.769(4) A?, c = 9.263(1) A?, β = 113.17(1)°, and Z = 4. The final conventional unweighted residuals are 0.037 (1), 0.040 (2), and 0.035 (3).