On the Reliability of C−H···O Interactions in Crystal Engineering:  Synthesis and Structure of Two Hydrogen Bonded Phosphonium Bis(aryloxide) Salts

Abstract

W This paper contains enhanced objects available on the Internet at http://pubs.acs.org/crystal. ABSTRACT: Two related phosphonium aryloxides, [Ph 3 PCH 3 ] + 2 [CH 2 (C 6 H 2 -3,5-tert-butyl-4-O) 2 ] 2-, 1a, and [Ph 3 -PC 2 H 5 ] + 2 [CH 2 (C 6 H 2 -3,5-tert-butyl-4-O) 2 ] 2-, 1b have been synthesized by protonation of nonstabilized phosphorus ylides with 4,4′-methylenebis(2,6-di-tert-butylphenol) LH 2 . The crystal structures of 1a and 1b have been determined by single-crystal X-ray diffraction, and that of 1b has also been determined by low-temperature (20 K) neutron diffraction. Both crystallize as CH 3 CN solvates, and both exhibit polymeric supramolecular structures via extensive C-H‚‚‚O hydrogen bonding. The predominant structural motif is chelation of the aryloxide oxygen atom of the anion by phosphonium alkyl and aryl C-H groups, such as has been previously observed for phosphonium monoaryloxide salts. The use of this motif as a supramolecular synthon in crystal engineering is explored. In the case of 1a, in addition to the expected intermolecular C-H‚‚‚O hydrogen bonding pattern, C-H‚‚‚π interactions between the anion and this solvent are observed. In the structure of 1b, C-H‚‚‚π interactions between the cation and anion lead to an unpredicted supramolecular structure. The possible significance of this feature is discussed the context of the general use of weak hydrogen bonds in crystal engineering.

Inclusion of pyridine and acetone by a diol host: structure, thermal stability and kinetics of desolvation

“…The compounds are shown in Scheme 1. 13,14 The host is in a trans-configuration, with a torsion angle O1-C15-C159-O19 = 165.5u.…”

Crystal engineering of two-dimensional polar layer structures: hydrogen bond networks in some N-meta-phenylpyrimidinones

“…31 The parallel alignment of dipoles in these crystal structures is explained through weak hydrogen bonds.z Two-dimensional layered structures assembled with O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds in crystals of uronium salts, imidazole carboxylates and urea derivatives have been reported. 15,16 We have shown in this paper the recurrence of 2D polar networks in N-aryl pyrimidinone crystals, thereby emphasising that robust and reliable C-HÁ Á ÁO synthons offer an equally effective crystal design theme 32 as the strong hydrogen bonds. The role of steric and/or electronic effects in hydrogen bonding and crystal packing has been examined by the systematic variation of functional groups in a family z Non-linear dielectric property in hydrogen-bonded chains may be established with strong O-HÁ Á ÁO, N-HÁ Á ÁO (KH 2 PO 4 , urea) or weak C-HÁ Á ÁO, C-HÁ Á ÁN bonds (ref.…”

Neutron fibre diffraction studies of amyloid using H2O/D2O isotopic replacement

“…The details and scope of these instruments are described in general terms by Teixeira, Zaccai et al (2008), Forsyth, Mason et al (2001) and Mason et al (in preparation). The new D19 diffractometer has been used in numerous neutron fibre diffraction studies of synthetic and biological polymers (Gardner et al, 2004;Nishiyama et al, 2008), for a wide range of problems in structural chemistry (Ahrens et al, 2001;Broder et al, 2002) and, more recently, for neutron protein crystallography (Kovalevsky et al, 2010). Dewhurst (2010) describes D22 in detail.…”