Diastereotopic groups in two new single-enantiomer structures (R2)P(O)[NH-(+)CH(C2H5)(C6H5)] (R = OC6H5 and C6H5)

The crystal structures of two single-enantiomer compounds, i.e. diphenyl [(R)(+)-alpha-ethylbenzylamido]phosphate, C21H22NO3P or (C6H5O)(2)P(O)[NH-(R)-(+)CH(C2H5)(C6H5)] (I), and N-[(R)-(+)-alpha-ethylbenzyl]-P,P-diphenylphosphinic amide, C21H22NOP or (C6H5)(2)P(O)[NH-R-(+)CH(C2H5)(C6H5)] (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 center dot center dot center dot 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 C-13/H-1 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.