Synthesis and structure of and DFT-studies on 1,3,5-[P(O)(i-PrO)2]3C6H3 and its CHCl3 adduct: analysis of the Cl3C–H· · ·OP hydrogen bond

The novel triphosphonic ester 1,3,5-[P(O)(i-PrO)2]3C6H3 (1) was synthesized and fully characterized including single crystal X-ray diffraction analysis. Crystallization in the presence of CHCl3 gave the corresponding solvate, 1·CHCl3, which shows moderate C–H· · ·OP hydrogen bonding. The hydrogen bond strength in 1·CHCl3 and the model compound [P(O)(i-PrO)2]C6H5·CHCl3 (2·CHCl3) were analyzed using RHF, DFT and MP2 methods. The calculated C–H· · ·OP hydrogen bond strength is in the range 5–6 kcal mol21, which is comparable with hydrogen bond strength in the water dimer but higher than in comparable C–H· · ·OC aggregates. q 2004 Elsevier B.V. All rights reserved.