STRUCTURAL STUDIES OF THE BISIMIDAZOLE METHYL-1,3,2-DIOXAPHOSPHORINANE-2-THIOXO-2-HYDROXY COMPLEX

The molecular complex of imidazole (Im) with methyl-1,3,2-dioxaphospho rinane-2-thioxy-2-hydroxy acid (DPTHA) involves strong (O-H ... H and N .. H+... N) and weak (C-H ... O and C-H ... S) hydrogen bonds and ha s an unusual molecular packing. The crystals are monoclinic, space gro up 12/m, with a = 10.609(5) Angstrom, b = 11.1739(2) Angstrom, c = 14. 069(7) Angstrom, beta = 95.47(2)degrees, V= 1660.1(11) Angstrom(3), Z= 8, D-c = 1.274 g/cm(3), F(000) = 672, and mu = 2.760 mm(-1). A compari son of C-13 CP/MAS NMR data for imidazole and the Im Hf Im cation show s that the C-13 isotropic chemical shifts of the C4 and C5 carbons, an d of the delta(22) and kappa parameters for C2 carbons for each compou nd are different. GIAO calculations at the HF/6-311(+)G(2d,p)//B3LYP/6 -31G level reveal correlations between the differences in the C-13 ch emical shift between the C4 and C5 atoms, the values of delta(22) and kappa for the C2 carbon, and the N ... H+ distance. An analysis of C-1 3 chemical shift parameters provides information about the strength of the hydrogen bonds and the localization of the proton in the N ... H... N linkage.