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.
A pairwise alignment of molecules in the crystal structure of the title ylide suggests the existence of mutual C-H-*C interactions between acidic o-Ph groups of one molecule and the basic carbanionoid centre of the other, an interpretation which is supported by examination of previously reported X-ray data.
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