Abstract. M= La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Isomorphous, hexagonal P63/m , Z = 2, 2(Mo K~) = 0.71069 A. M = La: M r = 676.40, a=14.045(1), c=7.0996(5) A, V= 1212.8 (2) A 3, D x = 1.852 g cm -3, /2 = 20.97 cm -1, F(000) = 684, R =0.020, 1560 reflections. M=Lu" Mr=712.46, a=13.834(1), c=6.9612(8) A, V= I153.8 (3) A 3, D x= 2.051 g cm -a, g = 46.30 cm -l, F(000) = 712, R =0.020, 1438 reflections. The lanthanide ions are coordinated by nine water molecules, with the coordination polyhedron having 6 (C3n) symmetry. The metal-oxygen distances decrease with increasing atomic number, and correlate well with the ionic radius of the metal. The ethyl sulfate ions are hydrogenbonded to the water molecules coordinating the metal ion. Probability-plot analysis shows that the geometry of the ethyl sulfate ion is independent of both the structure and the temperature in the range 171-298 K. Hydrogen atoms were located using difference Fourier syntheses, and were successfully refined.0108-2701/84/050781-06501.50

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The structure of NaLaIII(SO4)2.H20 consists of distorted Na-O6 octahedra, La-O9 complexes in the form of distorted tricapped trigonal prisms, and slightly irregular tetrahedral sulfate ions. All bond distances fall within normal limits. The sulfate ions manifest rigid-body behavior but this is not the case for either of the cation complexes. The single water molecule is modelled as having O-atom disorder but an ordered H atom. Hydrogen bonds involve only sulfate O atoms as acceptors. The absolute structure has been determined. Comment

Abstract.[Cu(H20)6](BrO3)2, M,=427"44, cubic, Pa-3, a = 10.3240 (6) A, V = 1100.38 (4) A 3, Z = 4, Dx=2"580gcm -3, A(MoK~)=0.71073A, /~= 92.32 cm-l, F(000) = 828, T = 296 K, R = 0.038 for 336 unique reflections having I > trz. The single type of copper ion (site symmetry 3) is coordinated by six water-molecule O atoms, each at an observed distance of 2-079 (4)A, in an array which is virtually regular octahedral, the nominal 90 ° angles measuring 89.95 (15) and 90.05 (15) °. Thus, this is not a typical Cu" complex in which (consistent with a static JahnTeller effect) a distorted octahedral array displays '(2 + 2 + 2)' coordination; rather, it is the sixth strict example of a CuII static structure inconsistent with the Jahn-Teller theorem. The presence of a dynamic Jahn-Teller effect is supported by the data. The single type of bromate ion has an observed Br---O bond length 1.649 (3)A and O--Br--O bond angle 104.17 (15) °. The bromate ion was found to manifest rigid-body behavior but, consistent with a dynamic Jahn-Teller effect, the copper-oxygen complex did not. The Br---O bond length corrected for rigid-body motion is 1.663 A. Refinement of the positional parameters of the two inequivalent H atoms permitted a detailed analysis of hydrogen bonding, which occurs principally between the oxygen octahedra and the bromate groups. This structure is isomorphic with those of hexaaquanickel(II) chlorate, hexaaquacobalt(II) bromate and hexaaquanickel(II) bro-

In the structure of the phthalide form of 2-acetylbenzoic acid, C9H803, there is a single type of hydrogen bond. Each molecule donates one and accepts one hydrogen bond. The hydrogen-bonded molecules form sets of puckered ribbons running along the c direction which are not crosslinked to each other. The dihedral angle between the planes of adjacent molecules along a hydrogen-bonded ribbon is 77.4 (1) °. CommentThis study of 2-acetylbenzoic acid is one of a continuing series on hydrogen bonding in carboxylic acids. As expected on the basis of the organic chemical literature, this acid crystallized in its phthalide form, (I). The only previous report on this structure (Gupta & Prasad, 1970) gave somewhat approximate cell parameters and a space-group assignment in agreement with the present results, but provided no atomic coordinates or structural analysis.