Diastereotopic groups in two new single-enanti­omer structures (R (2))P(O)[NH-(+)CH(C(2)H(5))(C(6)H(5))] (R = OC(6)H(5) and C(6)H(5))

The crystal structures of two single-enanti­omer compounds, i.e. diphenyl [(R)-(+)-α-ethyl­benzyl­amido]­phosphate, C(21)H(22)NO(3)P or (C(6)H(5)O)(2)P(O)[NH-(R)-(+)CH(C(2)H(5))(C(6)H(5))] (I), and N-[(R)-(+)-α-ethyl­benz­yl]-P,P-di­phenyl­phosphinic amide, C(21)H(22)NOP or (C(6)H(5))(2)P(O)[NH-R-(+)CH(C(2)H(5))(C(6)H(5))] (II), were studied. The different environments at the phospho­rus atoms, (O)(2)P(O)(N) and (C)(2)P(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 C(6)H(5)O/C(6)H(5) groups in I/II were considered: geometry parameters, contributions to the crystal packing, solution (13)C/(1)H NMR chemical shifts, conformations, and NMR coupling constants. The phospho­rus-carbon coupling constants (n)J (PC) (n = 2 and 3) in I and (m)J (PC) (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.