10.1021/ja045936c.s001 Massimo Boiocchi Massimo Boiocchi Laura Del Boca Laura Del Boca David Esteban Gómez David Esteban Gómez Luigi Fabbrizzi Luigi Fabbrizzi Maurizio Licchelli Maurizio Licchelli Enrico Monzani Enrico Monzani Nature of Urea−Fluoride Interaction:  Incipient and Definitive Proton Transfer American Chemical Society 2004 Bu urea deprotonation tetrabutylammonium salt CH 3 COO H 2 PO 4 stability decreases C 6 H 5 COO formation HF 2 HSO 4 HCO MeCN solution 2004-12-22 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Nature_of_Urea_Fluoride_Interaction_Incipient_and_Definitive_Proton_Transfer/3311230 1,3-bis(4-nitrophenyl)urea (<b>1</b>) interacts through hydrogen bonding with a variety of oxoanions in an MeCN solution to give bright yellow 1:1 complexes, whose stability decreases with the decreasing basicity of the anion (CH<sub>3</sub>COO<sup>-</sup> > C<sub>6</sub>H<sub>5</sub>COO<sup>-</sup> > H<sub>2</sub>PO<sub>4</sub><sup>-</sup> > NO<sub>2</sub><sup>-</sup> > HSO<sub>4</sub><sup>-</sup> > NO<sub>3</sub><sup>-</sup>). The [Bu<sub>4</sub>N][<b>1</b>·CH<sub>3</sub>COO] complex salt has been isolated as a crystalline solid and its molecular structure determined, showing the formation of a discrete adduct held together by two N−H···O hydrogen bonds of moderate strength. On the other hand, the F<sup>-</sup> ion first establishes a hydrogen-bonding interaction with <b>1</b> to give the most stable 1:1 complex, and then on addition of a second equivalent, induces urea deprotonation, due to the formation of HF<sub>2</sub><sup>-</sup>. The orange-red deprotonated urea solution uptakes carbon dioxide from air to give the tetrabutylammonium salt of the hydrogencarbonate H-bond complex, [Bu<sub>4</sub>N][<b>1</b>·HCO<sub>3</sub>], whose crystal and molecular structures have been determined.