Molecular Cocrystals of Carboxylic Acids. XIII. Spectral Characterization of the Adducts of Triphenylphosphine Oxide With Substituted Benzoic Acids and the Crystal Structures of the 1 : 1 Adducts With 2,4,6-Trinitrobenzoic Acid and 3,5-Dinitrobenzoic Acid

Abstract

The 1:1 adducts of triphenylphosphine oxide with the 2-, 3- and 4-nitro-, 3,5-dinitro-, and 2,4,6-trinitro-substituted benzoic acids have been prepared, and characterized by infrared and ³¹P n.m.r. spectroscopy. The crystal structures of two of these adducts, (triphenylphosphine oxide-3,5-dinitrobenzoic acid) and ( triphenylphosphine oxide-2,4,6-trinitrobenzoic acid), have been determined by X-ray diffraction. In all examples, the presence of single directed hydrogen bonds between the phosphoryl oxygen and the carboxylic acid proton is confirmed. For the X-ray structures, the O…O distances are 2.54(4) and 2.55(1)Ǻ respectively. Solid-state ³¹P n.m.r. spectroscopy has also proved a convenient technique for the detection of the presence of a single conformational adduct type in cocrystals.