The shortest C–H···O hydrogen bonds yet determined by single crystal neutron diffraction: a structural study of two phosphonium aryloxides

On the Interaction between N-Heterocyclic Carbenes and Organic Acids: Structural Authentication of the First N−H⋅⋅⋅C Hydrogen Bond and Remarkably Short C−H⋅⋅⋅O Interactions This work was supported by the EPSRC (UK) (J.A.C.), the Royal Society (M.G.D., J.A.K.H.), the NSERC (J.A.C.C.), Simon Fraser University (J.A.C.C.), Acadia University (R.L.W.H), and the University of Bath (S.P.R.).

“…The crystal structure of 4 4a contains two cations and two anions in the asymmetric unit, together with toluene and hexane solvent molecules in the lattice (Figure 1). The structural parameters within both cation and anion are unremarkable and consistent with those observed previously in other salts,1a, 3 although 4 is, to our knowledge, the first structurally characterized example of an imidazolium aryloxide. Of more interest are the close contacts between the ions—ion pairs are associated through C−H⋅⋅⋅O interactions: C(1)‐H(1)⋅⋅⋅O(1): D =2.801(4), d =1.87(3), θ =175(2); C(4)‐H(4)⋅⋅⋅O(2): D =2.842(4), d =1.88(3), θ =169(2).…”

“…Secondary C−H⋅⋅⋅π interactions, involving alkenyl C−H groups of cations and the aryl rings of anions, complete the polymeric supramolecular structure of 4 (C(2)‐H(2)⋅⋅⋅X: D =3.041, d =2.21, θ =146; C(5)‐H(5)⋅⋅⋅X: D =3.184, d =2.30, θ =149; where X=centroid of C(71)‐C(76) and C(51)‐C(56), respectively). Similar but longer‐range C−H⋅⋅⋅π interactions have been observed previously for the cation, with a cyclopentadienyl counteranion,8 and for the anion, with a phosphonium countercation 1a…”

“…To our knowledge, these interactions are significantly shorter than any previously reported hydrogen bonds between C−H donors and O acceptors 5. For example, very short and approximately linear C−H⋅⋅⋅O interactions have been noted in [(NO 2 ) 3 CH] 2 ⋅dioxane,6 (Ph 3 SiC≡CH⋅OPPh 3 ),7 and [(Ph 3 PCH 3 ) + (2,6‐Ph 2 C 6 H 3 O) − ]1a for which the minimum C⋅⋅⋅O separations are 2.94, 3.02, and 3.02 Å, respectively. Secondary C−H⋅⋅⋅π interactions, involving alkenyl C−H groups of cations and the aryl rings of anions, complete the polymeric supramolecular structure of 4 (C(2)‐H(2)⋅⋅⋅X: D =3.041, d =2.21, θ =146; C(5)‐H(5)⋅⋅⋅X: D =3.184, d =2.30, θ =149; where X=centroid of C(71)‐C(76) and C(51)‐C(56), respectively).…”

Non‐Coordinated Phenolate Anions and Their Application in SF6 Activation

“…All attempts to isolate the phenolate anion were thwarted by the selective formation of the phenol‐phenolate adduct (Figure 1, left) [11] . Davidson applied phosphonium ylides for the deprotonation of phenols resulting in salts featuring short cation‐anion C−H⋅⋅⋅O − hydrogen bonds [17, 18] . In addition to that, numerous substituted phenol derivatives containing electron‐withdrawing groups, thus featuring an increased acidity, were investigated [6, 19] …”

Supramolecular architectures with ladder and lamellar topologies using metal-ligand coordination units via C–H···Cl and O–H···Cl hydrogen bonding

“…6b). Furthermore, the ionic perchlorate present provides sites for additional O-H···O (hydrogens from metal-bound water) [2,28,50,51] and C-H···O [C-H (pyridyl 5-H)] hydrogen-bonding interactions [2,13,28,[52][53][54][55][56]. In essence, these perchlorates act as ionic molecular clips to afford 3D supramolecular multiple lamellar sheet architecture (Fig.…”