The typical crystal structures of a few representative α-aryl-α-hydroxyphosphonates

The crystal structures of seven α-aryl-α-hydroxyphosphonates synthesized by the Pudovik reaction of substituted benzaldehydes and dialkyl phosphites, namely dimethyl [(hydroxy)(phenyl)methyl]phosphonate, C₉H₁₃O₄P, dimethyl [(3,4-dimethoxyphenyl)(hydroxy)methyl]phosphonate, C₁₁H₁₇O₆P, dimethyl (1-hydroxy-1-phenylethyl)phosphonate, C₁₀H₁₅O₄P, dimethyl [1-hydroxy-1-(4-nitrophenyl)ethyl]phosphonate, C₁₀H₁₄NO₆P, dibenzyl [hydroxy(2-nitrophenyl)methyl]phosphonate, C₂₁H₂₀NO₆P, dibenzyl [(3-chlorophenyl)(hydroxy)methyl]phosphonate, C₂₁H₂₀ClO₄P, and dibenzyl [hydroxy(4-methylphenyl)methyl]phosphonate, C₂₂H₂₃O₄P, were studied to gain a better understanding of the organization in this type of molecule in the solid state. The crystals obtained for this series of compounds show a balance between C-OH...O=P chain-linked packing and the dimeric types of hydrogen-bond bridges of intermolecular pairs of such functions. The description is based on primary graph-set descriptors. Using graph-set descriptors one level deeper (i.e. secondary graph sets of the C-H...O type) revealed a similarity in the graph-set descriptors, suggesting a fine interplay of substituent- and shape-dependent effects on strong-weak interactions. It seems that the formation of chains or dimers is governed not only by the presence of a tertiary Cα atom, but also by the nature and crowding of the ortho substituents of the α-aryl group.