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The article describes (1) the wave-optical principles and the geometric interpretation which explain the diffraction pattern obtained when X-rays strike a crystal; (2) the experimental data which are the Miller indices h and the intensities of the diffracted beams I h ; (3) the Patterson method and the direct methods used to determine a model of the crystal structure for small and medium size molecules; and (4) the completing and refining the model structure until the calculated values and the experimental values are in good agreement.

Cyclohexanone semicarbazone (CSC), C 7 H 13 N 3 O, and 4-tert-butyl-cyclohexanone (BCSC), C 11 H 21 N 3 O, each adopt a slightly distorted chair conformation, with an increase of the total puckering of the six-membered ring for BCSC. The two crystal structures are very similar, with the NHCONH 2 groups connected in infinite ribbons through O...H-N hydrogen bonds, with distances in the range 2.84-3.12 A. The conformation adopted by the C=O bond with respect to the N-N bond is trans in both crystals

The structures of the olefinic complexes of platinum(II) withcis-but-2-en-1,4-diammonium, [PtCl3(C4H12N2)]+, and withcis-pent-2-enylammonium, [PtCl3(C5H12N)], the first one as its chloride, have been determined by single-crystal X-ray methods. The compounds form yellow monoclinic crystals, witha=11.238(3),b=12.234(4),c=7.769(1) A, β = 112.99(2) ° anda= 11.530(3),b=9.037(3),c= 10.067(3) A, β=105.50(2) °, respectively; both crystallize in the space groupP21/c withZ=4. The structures, solved by standard methods, have been refined anisotropically by full-matrix least-squares methods, both toR=0.040, on, respectively, 1808 and 1849 independent reflections collected by counter methods.

The crystal and molecular structures of the title compounds, [PtCl3(C3H8N)] (I), [PtCl3(C4H10N)] (II), and [PtCl3(C6H14N)] (III) have been determined by single-crystal X-ray methods. I crystallizes in the orthorombic system (Pbca) with a 10.444(3), b 8.782(2), c 17.036(5)A, Z 8; II is monoclinic (P21/n) with a 7.953(5), b 11.254(6), c 10.722(6)A, β 111.07(4)°, Z 4; III is orthorombic (P212121) with a 17.080(6), b 6.768(2), c 9.541(4)A, Z 4. Full-matrix least-squares refinements have given final R-factors of 0.051 (1077 reflections for I), 0.043 (1325 reflections for II) and 0.041 (1123 reflections for III). The reflections were collected by counter methods and only those having I τ 3σ(I) were used in the analyses. In all three complexes platinum is four-coordinate, having as ligands the three chlorine atoms and the double bond of the (n=1, 2 or 4) cationic species. The structures are discussed, and compared with that of the analogous complex containing the pent-4-enylammonium cation, .

The crystal and molecular structures oftrans-[PtCl2(C2H4)(4-MeC5H4N)] (I) andtrans-[PtCl2(C2H4)(2,4,6-Me3C5H2N)] (II) have been determined by single-crystal x-ray methods.I crystallizes in space groupP21/c witha= 4.991(1), b=21.658(3), c=10.675(3) A, β=110.17(2) °,Z=4;II is orthorhombic (Pbca) witha=10.295(6),b=12.393(8),c=20.370(10) A,Z=8.

The molecular structure of the title compound has been determined by X-ray crystallography. The crystals are monoclinic, space group P21/a, with a = 10.818(1), b = 9.062(1), c = 11.822(1) Å, β = 91.87(1)°, Z = 4. The structure has been solved by direct methods and refined by least-squares techniques to R = 0.0469 on 1684 counter intensities. Crystallographic data analysis demonstrates that in the solid state the δ-lactone adopts a distorted half-chair conformation due to the planarity of the carbonyl group, and the benzene ring is in the axial position. The mutual orientation of the lactone ring and the phenyl substituent obtained by potential energy calculations and by NMR spectroscopic analysis is in agreement with the results of the present study.

The structure of the olefin complex, [PtCl3(C4H12N2)]+, of platinum(II) with the trans-but-2-en-1,4-diammonium cationic ligand, has been determined as its hemihydrate chloride salt, by single-crystal X-ray methods. The compound [PtCl3(C4H12N2)]Cl,½H2O forms yellow monoclinic crystals, a= 23·911, b= 6·942, c= 13·586 A, β= 102·07°, space group C2/c with Z= 8. The structure, solved by standard methods, has been refined anisotropically by full-matrix least-squares methods to R 0·037, by use of 2447 independent reflections collected by counter methods.The structure contains discrete ions linked into infinite two-dimensional layers by chains of O–H ⋯ Cl, N–H ⋯ O, N–H ⋯ Cl hydrogen bonds. In the cation, platinum is four-co-ordinate with the three chlorine atoms and the double bond of the unsaturated diammonium cationic ligand. The structure of the complex is discussed together with the changes in the olefin caused by co-ordination. Comparison with similar platinum(II)–olefin complexes is made.

A three-dimensional X-ray structure determination of trichloro(cis-but-2-enylammonium)platinum(II), PtCl3(C4H10N), is reported. The compound crystallizes in the space group C2h5−P2 1 c of the monoclinic system with four formula units in a cell of dimensions a = 7.2254(4), b = 7.521(1), c = 16.596(1) A, β = 97.77(2)°. The calculated density (2.777 g. cm-3is good agreement with the observed density of 2.79± 0.01 g. cm−3. Data were collected by the equi-inclination Weissenberg technique and intensities were estimated. visually. The structure was refined by block-diagonal matrix least-squares methods to a final conventional R factor of 8.0% for 1381 observed reflactions. The structue consists of discrete squareplanar PtCl3(C4H10N) molecules in which the platinum the three chlorine atoms and the midpoint of the olefinic double bond form a plane, with the platinum, at the centre. The structure is compared with that of the analogous trichloro (trans-but-2-enylammonium)platinum(II).

Die Umsetzung des Iridium-Komplexes (I) mit den Phosphinen und Arsinen (II) ergibt die Komplexe (III), aus denen durch Anionen-Austausch die Komplexe (IV) entstehen.

The preparation and the structure of an unusual trigonal bipyramidal complex, [Ir(Ph3P)(QP)][BPh4][QP = tris-(o-diphenylphosphinophenyl)phosphine], are reported.

The structure of the conjugate acid of nitron, C20H17N4+, has been determined in the form of its salt with cobalt(II) isothiocyanate. The compound [C20H17N4]2[Co(NCS)4] forms blue monoclinic crystals, a= 23·441, b= 10·557, c= 19·065 A, β= 106·90°, space group C2/c with Z= 4. The structure was solved by conventional Patterson and Fourier techniques, and was refined anisotropically by the block-diagonal matrix least-squares method to R 0·035, by use of 1402 non-zero reflections collected by counter methods. The compound consists of discrete [C20H17N4]+ and [Co(NCS)4]2– ions. The cation has the structure of a 1,4-diphenyl-3-phenylamino-1,2,4-triazolium ion. The anion is a slightly distorted tetrahedron. The structures of the two ions are discussed in terms of their bond distances.

Crystal of (C3H6S3), 3CuCl are shown by X-ray diffraction analysis to contain a two-dimensional network of cage units with an adamantane-like structure.