Arrays of PO Dipoles As a Recurrent Structural Motif in Bis-Diphenylphosphine Oxides, Established from Powder X-ray Diffraction
2010-08-04T00:00:00Z (GMT) by
Rationalization of the solid-state structural properties of odd members (n = 3, 5, 7) of the series Ph2P(O)(CH2)nP(O)Ph2 leads to insights concerning the structural determinants of this class of material, particularly with regard to the formation of preferred arrangements of PO dipoles. The odd members of this series are recalcitrant to the formation of single crystals of suitable size and quality for single-crystal X-ray diffraction, and modern techniques for carrying out crystal structure determination directly from powder X-ray diffraction data were essential for determining the structural properties of these materials. In the present work, nonsolvate crystal phases of the materials with n = 3 and 5 were prepared by appropriate solid-state desolvation processes (starting from hydrate and toluene solvate phases, respectively), yielding microcrystalline powders of the nonsolvate phase in each case. Structure determination was carried out directly from powder X-ray diffraction data, employing the direct-space genetic algorithm technique for structure solution followed by Rietveld refinement.