Extensive analysis of N—H...O hydrogen bonding in four classes of phosphorus compounds: a combined experimental and database study

Abstract

The N—H...O hydrogen bond is the characteristic interaction in the crystal structures of N -benzyl- P -phenyl- N ′-( p -tolyl)phosphonic diamide, C 20 H 21 N 2 OP or (C 6 H 5 )P(O)(NHCH 2 C 6 H 5 )(NHC 6 H 4 - p -CH 3 ), (I), diphenylphosphinic 1-methylpropylamide, C 16 H 20 NOP or (C 6 H 5 ) 2 P(O)[NHCH(CH 3 )(C 2 H 5 )], (II), ( S )-1-phenylethylammonium N -[( S )-1-phenylethyl]phenylphosphonamidate, C 8 H 12 N + ·C 14 H 15 NO 2 P − or [ S -(C 6 H 5 )CH(CH 3 )NH 3 ][(C 6 H 5 )P(O){ S -NHCH(CH 3 )(C 6 H 5 )}(O)], (III), and (4-methylbenzyl)ammonium diphenylphosphinate, C 8 H 12 N + ·C 12 H 10 O 2 P − or [4-CH 3 -C 6 H 4 CH 2 NH 3 ][(C 6 H 5 ) 2 P(O)(O)], (IV). This article focuses on the N—H...O hydrogen bonds by considering the structures of (I), (II), (III) and (IV), and reviewing their analogous compounds, including 43 (C)P(O)(N) 2 , 102 (C) 2 P(O)(N), 31 (C)P(O)(N)(O) and 96 (C) 2 P(O)(O) structures, deposited in the Cambridge Structural Database (CSD). For the structures with a (C)P(O)(N) 2 segment, only neutral hydrogen bonds were found in the CSD. The other three classes of compounds included both neutral and `charge-assisted' hydrogen bonds, and the (C) 2 P(O)(O) structures were particularly noticeable for a high number of cation–anion compounds. The overall tendencies of N...O distances in neutral and cation–anion compounds were compared. The N—H...O hydrogen-bond angles were also analyzed for the four classes of phosphorus compounds.