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The concept of chloro/methyl group interchange as a tool in crystal engineering is discussed with respect to derivatives of 2-benzyl-5-benzylidenecyclopentanone (1-4). A study of the mixed crystals containing either 1 and 2 (X) or 3 and 4 (Y) demonstrates that molecules which otherwise crystallize into photostable crystal structures may be incorporated into a light-sensitive form. Furthermore, such mixed crystals are demonstrated (using four-circle diffractometry) to undergo single-crystal --* single-crystal reaction with the formation of the product dimer molecules identified within the reactant lattice. The final R for X is 0.0418, for Y it is 0.0578, and for irradiated X it is 0.0394.It is clear that the controlled variation of the substituent groups present on an organic molecule may allow subsequent crystalli-zation into particular and desired packing arrangements2. One particular strategy for this so-called crystal-engineering concept 0002-7863/84/ 1506-3606$01Supplementary Material Available: Tables of final atomic parameters and lists of bond lengths, bond angles, and observed and calculated structure factors (33 pages). Ordering information is given on any current masthead page. 53-0. (1 1) Swiatkiewicz, J.; Eisenhardt, G.; Prasad, P. N.; Thomas, J. M.; Jones, W.; Theocharis, C. R.

Structures of the alkali-metal hydrates Li(HO)Z, LiK(HO)Z, Na(HO)Z, and Rb(HO)Z, unit cell parameters for RbZ and Rb(HO)Z, and the density functional theory (DFT)-optimized structures of KZ, K(HO)Z, RbZ, Rb(HO)Z, CsZ, and Cs(HO)Z are reported (Z = BF) and compared with previously reported X-ray structures of Na(HO)Z, K(HO)Z, and Cs(HO)Z. Unusually rapid room-temperature hydration/dehydration cycles of several MZ/M(HO)Z salt hydrate pairs, which were studied by isothermal gravimetry, are also reported. Finely ground samples of KZ, RbZ, and CsZ, which are not microporous, exhibited latent porosity by undergoing hydration at 24-25 °C in the presence of 18 Torr of HO(g) to K(HO)Z, Rb(HO)Z, and Cs(HO)Z in 18, 40, and 16 min, respectively. These hydrates were dehydrated at 24-25 °C in dry N to the original anhydrous MZ compounds in 61, 25, and 76 min, respectively (the exact times varied from sample to sample depending on the particle size). The hydrate Na(HO)Z also exhibited latent porosity by undergoing multiple 90 min cycles of hydration to Na(HO)Z and dehydration back to Na(HO)Z at 23 °C. For the KZ, RbZ, and CsZ transformations, the maximum rate of hydration (rh) decreased, and the absolute value of the maximum rate of dehydration (rd) increased, as T increased. For KZ ↔ K(HO)Z hydration/dehydration cycles with the same sample, the ratio rh/rd decreased 26 times over 8.6 °C, from 3.7 at 23.4 °C to 0.14 at 32.0 °C. For RbZ ↔ Rb(HO)Z cycles, rh/rd decreased from 0.88 at 23 °C to 0.23 at 27 °C. For CsZ ↔ Cs(HO)Z cycles, rh/rd decreased 20 times over 8 °C, from 6.7 at 24 °C to 0.34 at 32 °C. In addition, the reversible substitution of DO for HO in fully hydrated Rb(HO)Z in the presence of N/16 Torr of DO(g) was complete in only 60 min at 23 °C.

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The synthesis of high-purity NaBF and the crystal structures of Na(BF) (5 K neutron powder diffraction (NPD)), Na(HO)(BF) (120 K single-crystal X-ray diffraction (SC-XRD)), Na(BCl) (5 and 295 K NPD), and Na(HO)(BCl) (100 K SC-XRD) are reported. The compound Na(HO)(BF) contains {[(Na(μ-HO)Na(μ-HO))]} infinite chains; the compound Na(HO)(BCl) contains discrete [(HO)Na(μ-HO)Na(HO)] cations with OH···O hydrogen bonds linking the terminal HO ligands. The structures of the two hydrates and the previously published structure of Na(HO)(BH) are analyzed with respect to the relative coordinating ability of BF, BH, and BCl toward Na ions in the solid state (i.e., the relative ability of these anions to satisfy the valence of Na). All three hydrated structures have distorted octahedral NaX(HO) coordination spheres (X = F, H, Cl). The sums of the four Na-O bond valence contributions are 71, 75, and 89% of the total bond valences for the X = F, H, and Cl hydrated compounds, respectively, demonstrating that the relative coordinating ability by this criterion is BCl ≪ BH < BF. Differential scanning calorimetry experiments demonstrate that Na(BF) undergoes a reversible, presumably order-disorder, phase transition at ca. 560 K (287 °C), between the 529 and 730 K transition temperatures previously reported for Na(BH) and Na(BCl), respectively. Thermogravimetric analysis demonstrates that Na(HO)(BF) and Na(HO)(BCl) undergo partial dehydration at 25 °C to Na(HO)(BF) and Na(HO)(BCl) in ca. 30 min and 2 h, respectively, and essentially complete dehydration to Na(BF) and Na(BCl) within minutes at 150 and 75 °C, respectively (the remaining trace amounts of HO, if any, were not quantified). The changes in structure upon dehydration and the different vapor pressures of HO needed to fully hydrate the respective Na(BX) compounds provide additional evidence that BCl is more weakly coordinating than BF to Na in the solid state. Taken together, the results suggest that the anhydrous, halogenated closo-borane compounds Na(BF) and Na(BCl), in appropriately modified forms, may be viable component materials for fast-ion-conducting solid electrolytes in future energy-storage devices.