a 0.4 I L 3800 3800 3700 3600 3500 3400 +/cm-'-Figure 5. Comparison of the OH regions of the IR spectra ofactivated cloverite (a) and Y zeolite (b. Linde LZY62, Si/Al = 2.4). The spectra were normalized to 10 mg solid, and based on the structures of the solids the ratio between the area of OH bands in cloverite and Y zeolite should be at least approximately 1 :3; however, the observed value is only 1 :40. I = Absorbance.In conclusion, this study reveals that the postulated terminal OH groups in the framework of cloverite are not detectable by IR spectroscopy. Free OH groups, in particular those due to POH groups that vibrate at 3676 cm-', are observed before and after activation of cloverite at 573 K under ozone. Their number increases upon activation but remains quite low, about 3.5 % of the expected number, indicating that they correspond to defect sites. This study does not cast doubt on the results of the X-ray structure analysis, but rather on whether the terminal oxygen atoms in the structure really belong to hydroxyl groups.Many microporous main group oxides have been prepared by hydrothermal synthesis"] but it has long been a goal to produce lacunary materials with modulated catalytic activity by constructing frameworks with d-block metals in close proximity to the voids. Haushalter et al. have shown how this can be achieved for vanadium and molybdenum phosphates.['] The usefulness of superheated fluids for preparing extended frameworks based on metal-ligand interactions has recently been demonstrated both by ourselvesL3] and and we now wish to report the extension of this technique to the preparation of a cobalt squarate with a microporous structure. The cobalt -squaric acid system has been extensively investigated under ambient condit i o n~'~] and gives compounds based on the framework found in 1 in most cases; analogous structures are also formed by the corresponding compounds of manganese, iron, nickel, and zinc. We report herein on compound 2, which has a structure unlike those previously observed.

The two compounds [Cr3O(OOCCH3)6(H2O)3]Cl·6H2O and [Fe3O(OOCCH3)6(H2O)3]Cl·6H2O are the prototypes of the general class of trinuclear “basis carboxylates”. New single-crystal X-ray structure determinations show that the two compounds are strictly isomorphous, with little disorder, and make it possible to quantify the extents of distortion of the molecules from idealized trigonal geometry.

The crystal structures of AMnF4 compounds (A = K, Rb, Cs) were determined by X-ray diffraction on twinned single crystals: The K and Rb compound are isostructural: space group P21/a, Z = 4; KMnF4: lattice constants a = 769.9(2), b = 764.4(2), c = 576.9(1) pm, β = 90.54(3)°; R/wR = 0.029/0.025 for 481 reflections; pseudomerohedral (100) twin. RbMnF4: lattice constants a = 782.2(5), b = 777.7(3), c = 605.0(2) pm, β = 90.83(4)°; R/wR = 0.0665/0.0513 for 471 reflections. The structure of CsMnF4 has been refined anew in the space group P4/n (Z = 4) as a merohedral (110) twin (lattice constants a = 794.40(6), c = 633.76(9) pm; R/wR = 0.051/0.044 for 820 reflections). All three structures derive from the T1A1F4 type and show puckered [MnF4]- layers with an antiferrodistortive order of strongly Jahn-Teller distorted [MnF6] octahedra. The elongated axes (Mn-F for KMnF4: 215.8, RbMnF4 215.2, CsMnF4216.8 pm) alternate with shorter ones (188.1,188.3,185.4 pm) within the layer planes. The terminal Mn-F bonds are very short (180.3, 180.6,181.7 pm). The Mn-F-Mn bridging angles are 140.6° and 146.4° for the K, 148.3° and 152.1° for the Rb, and 161.9° for the Cs compound. The magnetostructural relations and the three puckering types are discussed for all the AMnF4 layered structures.

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An X-ray single crystal structure determination (monoclinic, space group P21/c, a = 573.6(2), b = 489.2(1), c = 574.8(2) pm, β = 108.07(2), Z = 2; wR = 0.038 for 380 reflections) shows that NaMnF4 crystallizes in the same layered structure type as LiMnF4. In the quadratic layers the Mn-F-Mn bridges are strongly asymmetric, due to the Jahn-Teller effect, leading to an antiferrodistortive order of elongated octahedra. The bridging angle is 138.4°. The Na+ ions are 6-coordinated as well. The common structural arrangement of both [MnF6] and [NaF6] octahedra shows topological relation to the rutile structure. In the magnetic measurements performed on powder samples NaMnF4 behaves as an antiferromagnet with a weak ferromagnetic component below 13 K. By neutron diffraction on powder (4-70 K) a magnetic cell doubled along the α-axis is found and below a Neel temperature of TN = 13 K the magnetic structure shows colinear antiferromagnetic arrangement of the spins pointing slightly (16) out of the layer plane. The resulting magnetic moment is 3.52 μΒ.