The crystal structures of two single-enantiomer compounds, i.e. diphenyl [(R)-(+)-\\\\a-ethylbenzylamido]phosphate, C21H22NO3P or (C6H5O)2P(O)[NH-(R)-(+)CH(C2H5)(C6H5)] (I), and N-[(R)-(+)-\\\\a-ethylbenzyl]-P,P-diphenyl phosphinic amide, C21H22NOP or (C6H5)2P(O)[NH-R-(+)CH(C2H5)(C6H5)] (II), were studied. The different environments at the phosphorus atoms, (O)2P(O)(N) and (C)2P(O)(N), allow the P=O/P—N bond strengths to be compared, as well as the N—H...O=P hydrogen-bond strengths, and P=O/ N—H vibrations. The following characteristics related to diastereotopic C6H5O/ C6H5 groups in I/II were considered: geometry parameters, contributions to the crystal packing, solution 13C/1 H NMR chemical shifts, conformations, and NMR coupling constants. The phosphorus-carbon coupling constants nJPC (n = 2 and 3) in I and mJPC (m = 1, 2, 3 and 4) in II were evaluated. For a comparative study, chiral analogous structures were retrieved from the Cambridge Structural Database (CSD) and their geometries and conformations are discussed.

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