Crystal Structure of cis-2-[(P, P-Diethoxy) phosphono(m-nitro)benzyloxy]-4-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-sulfide

The crystal structure of the title compound cis-2-[(P, P-Diethoxy) phosphono(m-nitro)benzyloxy]-4-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-sulfide, C₂₂H₂₉NO₈P₂S, was determined by single crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P2₁/c, with M_r = 529.49, a = 9.888(2), b = 20.831(4), c = 12.797(3) Å, β = 94.42(3)°, V = 2628(1) ų, Z = 4, D_r = 1.338 g/cm³, λ = 0.71073 Å, μ = 0.2796 mm^-1 and F(000) = 556. The structure was solved by direct methods. The final R factor is 0.052 and R_w is 0.057 for 1793 unique observed reflections [I≥3σ(I)]. A cis-configuration and a preferred chair conformation for the molecule have been established by X-ray diffraction analysis. The results presented also give a good explanation to the correlation between the configurational assignments and the regularity in the chemical shifts of C₄-H and ³¹P NMR.