CRYSTALLOGRAPHYBy M. Gerloch and R. Mason(M.G.: Department of Chemistry, Un+versity of Manchester; and R. M. : Department ofChemistry, University of Shefwld)General CqstalIographic Developmenh.--UntiI a few years ago, thereexisted three major bottlenecks in the rapid and accurate determination bydiffraction methods of molecular structures of moderate complexity. Thefirst was the relatively slow process of data collection by conventional photo-graphic methods ; data collection and evaluation for an average structuredetermination could take up to three months and, except where special carewas taken, the data were of only limited accuracy (the average discrepancyin observed structure factor amplitudes might be 8-10%). In addition tothe moduli of the structure factor amplitudes, their phases had to be knownto reconstitute the image of the electron distribution in the unit cell andphase determination was a protracted procedure even when heavy atomderivatives were available (cf., proteins).The third bott’leneck, the pro-cessing of data, the extensive calculations involved in the calculation ofFourier series and least-squares analysis of various atomic parameters, hasbeen obviated by the advent of high-speed digital computers. AutomaticWactometers and the development of automated film densitometers arerelieving the tedium of data collection and, often, improving the accuracyof the structure-factor amplitude determination. More recently, new develop-ments in the general area of the phase problem have taken place.The term “direct methods” applies to procedures where phases arederived without any knowledge of atomic positions.The first realisationthat the amplitudes and phases of X-ray reflexions were related was that ofHarker and Kasper and Karle and Hauptman., These authors were con-cerned with precise analytical relationships between the phases of relatedreflexions but in 1952, C~chran,~ Sayre,* and Zachriasen laid the basis forsimple probability relationships between structure factors. In essence, ifthere are three “ strong ” reflexions of Miller indices (h1klZl), (h2k2Z2) and(4 + h,, kl + k,, ZI + ZJ, the sign-relationshipis probably true (in a centrospmetric structure the phase of an X-ray re-flexion is either 0 or z so that its sign is +1 or -1).The physical basis ofthis sign relationship equation is that the electron density is always ~ t e inthe unit cell.General reviews of the earlier work in direct methods have been given byD. Harker and J. S. Kasper, Acta Cryst., 1948,1, 70.J. Karle and H. Heuptman, Acta Cry&., 1950,3, 187.W. Cochran, Acta Cryst., 1952, 5, 65.D. M. Sayre, A& Cryst., 1952, 5, 60.W. H. Zaohariasen, Acta Cryst., 1952, 5, 68690 CRYSTALLOGRAPHYWoolfson 6 s who allows himself the final comment that “ when one hasexperienced the problems associated with sign determination, one realiseshow bleak is the outlook with the much more complex general phase-deter-great progress has been made in a practical direction.” Yet in the last threemonths a t least two non-centrosymmetric structures have been determinedby direct methods.One general procedure has been set out by Karle and Karle 8 and usedto determine the structure of ~anamine.~ This analysis, together with thatof isocremolactone,1° very largely relies on the so-called X2 and tangentformuh for the systematic building up of a substantial number of phasesfrom an original triplet whose phases can be specified arbitrarily.In pan-amine, a comparison of the phases determined by direct methods with thevalues computed from the final structure showed an average error of 22”for the 235 three-dimensional reflexions. These errors did not interfere withthe ready recognition of the panamine skeleton from the first electron densitysynthesis.The full power of these methods has not yet been realised and theremay be a strong case for combining them with other information such asmolecular packing.Several analyses recently completed represent the begin-nings of a breakthrough in phase determination, a t least for certain classesof structures which had previously proved intractable. Several workers arealready concerned with the application of these direct methods to largemolecules such as the proteins. In the past, the relevance of direct methodsto large molecule analysis was felt to be minimal because the structure-factor amplitudes were too small (defined in unitary structure-factor terms) ;the latest phase-determining formulz do not suffer as much from this restric-tion as the earlier ones and exploratory work on large structures wouldtherefore seem to be justified.Karle has also discussed methods for combining information from asingle isomorphous replacement with phase determining relations for non-centrosymmetric crystals 11 and for the evaluation of phases for structuredetermination by neutron diffraction where the formuh appropriate forX-ray diffractions are not immediately applicable, since atoms with bothpositive and negative scattering factors may be present for the neutrondiffraction results.12 A development of the Hauptman-Karle relationshipsconcerned with the equivalence of structure invariants has been given byHaup t m an.l3A new probability function for the structure-factor signs in centrosym-metrical crystals has been proposed and its relationship to the Hauptman-6 M.M. Woolfson, “ Direct Methods in Crystallography,” Oxford University Press,London, 1961.7 M. M. Woolfson, “ Tho Determination of Crystal Structures,” ed. H. Lipsoa andVJ. Cochran, Bell, London, 1966, p. 265.8 J. Karle and I. L. Karle, Acta Cryst., 1966, 21, 849.9 I. L. Karle and J. Karle, Acta Cryst., 1966, 21, 860.mining problem ” [in non-centrosymmetric crystal structures] ‘‘ . . . 2 no10 Yow-Lam Oh and E. N. Maslen, Tetrahedron Letters, 1966, 28, 3291.11 J. Karle, Acta Cryst., 1966, 20, 273.12 J. Karle, Acta Cryst., 1966, 20, 881.13 H. Hauptman, Acta Cryst., 1966, 20, 639GERLOCH AND MASON 691Karle and other probability functions discussed.14 A theory of the jointprobability distribution of complex-valued structure factors has beenderived.l5A method has been described l6 for solving the phase problem in thecentrosymmetric case by using the anomalous scattering of X-rays. Themethod, which requires the comparison of structure-factor amplitudesmeasured with two radiations, may be applied when the imaginary com-ponent of the anomalous scattering is too large to be neglected.The restraints on phases imposed when a molecule crystallises in Werentcrystal forms, or occurs more than once per asymmetric unit, has beenexamined.1’ Several analyses of proteins have recently used the so-calledrotation function,ls which represents the sum of a point-by-point productof two different Patterson functions rotated with respect to one another, inattempts to interpret the Patterson function; the symmetry of the rotationfunction has been discussed while Tollin19 has extended the methods fordetermining the positions of a known group of atoms in a molecular crystalwith respect to an arbitrarily chosen origin.The need for improving the accuracy of observed data for precise deter-minations of bond lengths and electron distribution studies is obvious andthe theory of the measurement of integrated intensities obtained with single-crystal counter d8ractomete.m has been discussed in terms of six com-ponents of the observed intensity profiles, There is a strong case for theuse of crystal-monochromatised radiation for investigating crystal struc-tures. Systematic errors in X-ray data are of particular concern; the effectof absorption errors in diffraction data on a structure refinement is verylargely on the atomic Debye factors, although some positional parameterswere also considerably in error.21 It cannot be over-emphasised to theaverage chemical reader of a crystallographic paper that the crystallo-grapher’s estimated standard deviations are often systematically under-estimated as the result of systematic errors in the X-ray data, the use ofapproximate least-squares matrices and so on.The fact that crystallo-graphers generally use atomic scattering factors based on the electrondistribution of non-bonded atoms is also a possible source of error in bondlengths (see, for example, ref. 22).Several publications deal with interesting topics on the questions ofmolecular packing and atomic and thermal motions in crystals.Kitajo-gorodsky23 has summarised his views on the packing of crystals in whichthe potential-energy calculation is based on the summation overall atom-atom intermolecular interaction potentials ; the possible extensions to thecalculation of vibrational spectra, elasticity and expansion tensors, as welll4 G. Allegra, Acta Cryst., 1965, 19, 949.Is S. Naya, I. Nitta, and Y. Oda, Acta Cryst., 1965, 19, 734.la A. C. Hazell, Acta Chem. Scand., 1966, 20, 170.l7 P. Main and M. G. Rossmann, Actu Cryst., 1966, 21, 67.l8 P. Tollin, P. Main, and M. G. Rossmam, Acta Cryst., 1966,20, 404.2o J. Ladell and N. Spielberg, Acta Cryst., 1966, 21, 103.21 R.C. Srivastava and E. C. Lingafelter, Acta Cryst., 1966, 20, 918.1a A. M. O’Connell, A. I. M. Rae, and E. N. Maslen, Acta Cryst., 1906, 20, 208.es A. Kitajgordsky. J . Chem. Phys., 1966, 63, 205.P. Tollin, Acta Cryst., 1966, 21, 613692 OBY STALLOGRAPHYas to thermodynamic properties of molecular crystals, is dso examined.Detailed calculations of dispersion and multipole interactions and repulsionpotentials in crystals of benzene and naphthalene have also been com-~leted.2~8 25The Debye-Waller factors of the ions in crystals of sodium chloride andcesium chloride have been commented upon. Pryor 26 suggests, that inspite of the difference between the core and shell vibration amplitudes, therewill not be EL detectable difference in the apparent Debye factors derivedfrom X-ray and neutron experiments.The equality of the mean-squareamplitude8 of czesium and chlorine derived from X-ray data from czesiumchloride 27 confirms the predictions of Waller to the effect that, for alkalihalides at high temperatures, the mean-square displacements are inde-pendent of the mass of the ions, depending only on the forces between them.There is increasing interest in the data relating to atomic and molecularmotions which may be derived from incoherent scattering measurements.For example, the inelastic scattering of neutrons by the cubic phase of(NH4).$iF6 shows a broad band at 168 8 cm.-l with a shoulder a t305 & 25 cm.-l; these are assigned to the 1-0 and 2-0 transitions of arotational motion of the ammonium ion.,8 Measurements of the infraredspectra and incoherent neutron scattering support previous evidence thatin DCr02 there are asymmetric hydrogen bonds while in HCrO, these areessentially symmetric.29Introduction.-We have, as usual, found it impossible to provide a trulycomprehensive summary of the structural work which has been completedby crystallogmphic methods. Reports dealing with such topics as mixedoxide systems, bronzes, alloys, and related topics have not been included.The inorganic section is divided into transition and non-transitionelements, lanthanides and actinides. Groups IIIa and Ib are included inthe transition series rather than in the main groups, and compounds arediscussed in groups of elements and, in the transition series, further sub-divided into complexes and organometallic molecules. The following list isonly indicative of coverage : eight co-ordinate nitrates of titanium and cobalt ;trigonal prismatic molecules [V(S2C2Ph,),, Mo(S,C,H,),, Re(S,C,Ph,),, andHf2S] ; rhenium clusters ; organometallic hydrides [HCr,(CO),,,- andHMn(C0)J ; boron hydrides, polyicosahedral boranes and carboranes in-cluding the metal complex (BgC,H,,)Re(CO),Cs ; five co-ordinate complexesof Fe, Coy Ni, Cu, and Zn; dicyclopentadienyl lead; the carbonyls, dodeca-carbonyl tri-iron and dodecacarbonyltetracobalt ; ally1 complexes ; many de-terminations of absolute configurations particularly of cobalt complexes ;numerous nickel-sulphur compounds ; a wide range of Schiff base complexes24 D.P. Craig, R. Mason, D. P. Santry, and P. Pauling, Proc. Roy. SOC., 1966, A ,286, 98.86 D. P. Craig, P. A. Dobosh, R. Mason, and D. P. Santry, Dbcws. Farday Soc.,1966, 40, 110.26 A. W. Pryor, Acta Cryst., 1966, 20, 138.27 Z . Barnea and B. Post, Acta Cryst., 1966, 21, 181.s* E. 0. Schlemper, W. C. Hamilton, and I. I. Rush, J . Chem. Phys., 1966,44,2499.99 I. I. Rush and J. R. Ferraro, J. Chem. Phys., 1966,44, 2496GERLOCH AND MASON 693of iron, nickel and, especially, copper; Ag-S-Ag-S-Ag chains in tristhiourea-silver(1) chloride and S-Tea chains in trisdimethyldithiophosphate ; thebichloride ion, HC1,- ; sulphur-nitrogen heterocycles; solid hydrogen anddeuterium ; a wide range of iron-organometallic complexes including car-bonyl, allyl, carbenes, and cumulene ligands and a number of interestingsilicate minerals.In the general area of organic molecules a high proportion of the reportsdeal with conformational studies rather than with the question of the X-raydetermination of electron distribution in molecules, and correlation ofobserved bond lengths with those predicted by various theoretical models.The geometry of the hydrogen bond, in a wide range of molecules, hasbeen specified in some detail including the quite accurate location of thehydrogen atom by X-ray and neutron diffraction measurements.Otherstudies of molecular interactions in the solid state include accounts of thepacking of aromatic hydrocarbons and charge-transfer complexes. A numberof crystallographic analyses point the way to the increased use of diffractionmethods to identify complex natural products.In the more biological area,substantial results are available on lysozyme and, only slight.ly less so, oncarboxypeptidase and insulin. The largest " molecule " so far studied,tobacco mosaic virus, is being specified in increasing detail and crystallo-graphic studies of DNA and RNA continue.1. INORGANIC STRUCTURESComplexes and Organometallic Molecules of Transition-metd Ions.Group III.-Seven-co-ordination of the scandium atoms in &OF has beenrep0rted.3~ Each scandium ion is surrounded by four oxygen and threefluorine atoms, the average distance being 2-10 and 2.20 respectively.The co-ordination polyhedra and the linking of the polyhedra resemble thosefound in ZrO,.A new ox~scandate,~~ MgSc,O,, has been prepared above 2000".Isotypicwith CaSc20, and CaFe,O,, it consists of a statistical distribution of Mg2fand Sc3+ ions in a rigid (SC,O,)~- framework.Group ma.-The molecular structure of (TiCl,,CH,CO,C,H,), consists ofdimeric molecules with double chlorine bridges. 32 Each titanium atom isoctahedrally co-ordinated by five chlorine atoms and a carbonyl oxygenatom of the ethylacetate; Ti-C1 distances range from 2-22-250 A with abridge Ti-CI bond length of 2.50A. The Ti-0 distance is 2-03A. Thestructure of bistrimethylaminetitanium tribromide has been cited 33 as anexample of the Jahn-Teller effect in pentaco-ordinate molecules. Themolecules are found to have essentially C,, symmetry, the distortion fromidealised of the trigonal bipyramid occurring within the planar equatorialTiBr, group ; Ti-Br bond lengths are 2-44 (2) and 2.40 (l), Br-Ti-Br angles30 B.Holmberg, Acta Chem. Sea&., 1966,20, 1082.31 H. Muller-Buschbaum, 2. unorg. Chem., 1966, 343, 113.3a L Brun, Acta Cryst., 1966, 20, 739.33 B. J. Russ and J. S. Wood, Chem. Cmm., 1966,745694 ORY S TALL0 GRAPHYare 121-3" (2) and 118" (1) , the Ti-N axial bond lengths are 2-27 8. Titaniumis eight-co-ordinate in anhydrous titanium(1v) nitrate ( l).34 Four sym-metrically bidentate nitrato-groups are arranged according to D,, (or per-haps Th) symmetry in a flattened tetrahedral manner. Dimensions of thenitrato-groups differ from those in a typical nitrate ion; mean N-0 for bondsadjacent to the metal is 1.292 and N-0 (outer) is 1.185 8, indicating a partialdouble-bond character of outer N-0 bonds, consistent with the unusuallyhigh stretching frequency of 1635 cm.-l in the infrared spectrum.Thestructure closely resembles the analogous cobalt complex.An analysis of i3-zirconium trichloride shows 35 the chlorine atoms form-ing a distorted hexagonal close-packed arrangement with 1/3 of the octa-hedral holes Ned by zirconium atoms to give infinite linear chains of ZrC1,octahedra-sharing faces; Zr-C1 distances are 2.55 8. The structure is cor-related with spectral and magnetic data. In Zr2(OH),(S04)3(H,0)4 sheets ofzirconium and sulphate ions are bridged by double hydroxide ions.36 Thereare essentially Zr2( OH),6+ dimers containing eight-co-ordinate zirconium inwhich oxygen atoms form a dodecahedron with triangular faces (equivalentto the Mo(CN)*4- coordination).The average Zr-0 distance is 2.19 8, andvery short 0-0 distances exist in the hydroxide bridges.In dihafniurn sulphide, Hf,S, each sulphur is surrounded by six hafniumatoms in a trigonal prismatic co-ordination.37 Each hafnium atom is in-volved in a distorted octahedral co-ordination by three other hafniums andthree sulphurs. Inter-atomic distances are Hf-Hf 3.06 and 3.37 8, Hf-S 2.63, and S-S 3.378.Group Va.-Two structures containing the decavanadate ion have beendetermined. In the first, the decavanadate ion is an isolated group of tencondensed V06 octahedra, six in a regular array sharing edges and four more,two fitted in above and two below by sharing sloping edges.The structureis based on a sodium chloride-like arrangement of vanadium and oxygenatoms and has a close relationship with other complex molybdates, niobatesThe structure is related to the anti-NbS, type.84 C. D. Garner and S. C. Wailwork, J . Chem. SOC. ( A ) , 1966, 1496.86 J. A. Watts, Inorg. Chem., 1966, 6, 281.D. B. McWhan and G. Lundgren, Inorg. Chem., 1966,5,284.H. F. Franzen and J. Graham, 2. Krkt., 1966,125, 133GERLOOH AND MASON 695and tantalates. The V06 octahedra distortions are analogous to the square-pyramid and special co-ordination features known in other vanadatestru~tures.~8 In the crystal structure of pascoite, the decavanadate groupV,0028 has orthorhombic D,,, symmetry and again consists of ten VOs octa-hedra sharing edges, basically the same as that in the zinc analogueK,~n,V100,8,16~,~.One calcium atom is co-ordinated to seven H20 mole-cules, two others linked to the decavanadate group through two apicaloxygen atoms on opposite sides of the group and each is also co-ordinatedto five water m0lecules.3~ The compound VMoO, is isostructural withMoOPO, and should be formulated 4O as VOMoO,. The structure consistsof V06 octahedra joined by apices to form chains which run parallel to thecrystal c-axis. Each octahedron is connected to four MOO, tetrahedra bysharing corners. The VO, octahedra are considerably distorted and mightbe considered as square pyramids. Trigonal prismatic co-ordination isobserved in V(S,C,Ph2),,41 the structure being very similar to Re(S,C,Ph,),and Mo(S,C,H,),.Other dithiolate-type complexes likely to share this co-ordination geometry are also discussed. The mean V-S distance is 2.338 wand S-V-S angle 81.7". Intra-ligand S-S vectors are 3.058 A while inter-ligand S-S contacts in the slightly distorted prisms are 2.927, 3-088 and3.178 8, these distances are also observed in the other two trigonal prismaticcomplexes.The complex arrangements of Nb~lO77E' and Nb170d2F have been com-pared.4, The Nbl,Ol,P structure contains two different blocks of Re0,-type,3 x 5 and 3 x 6 octahedra in size. In the Nb31077E' structure the blocks areof the same kind, 3 x 5 octahedral in size.In both structures the blocksare joined by additional edge-sharing and with metal atoms in tetrahedralco-ordination in the same way as in cc-Nb,O,. A refinement of the structureof K,NbF,, using three-dimensional neutron diffraction data has confirmedthe original X-ray geometry and reports improved bond lengths and Debyefactors for this seven-co-ordinate molecule.43 A feature of the structureanalysis of niobium subhalide, Nb,Ill, is that it contains the first known[i&X,]"+ group with a non-integral metal oxidation state.44 six Nb atomsare arranged octahedrally about a centre of symmetry while eight iodineatoms are located symmetrically above the triangular faces of the octahedron.The ion has exact Ci symmetry and each Nb has a formal oxidation state of+11/6.An analysis 45 of the crystal structure of NbOPO, shows corner-shared NbO, octahedra, linked by PO4 tetrahedra, giving a three-dimen-sional network.Rhombohedra1 lead metaniobate 46 also shows NbO, octahedra. Twooctahedra share an edge and the pairs then share four corners to complete38 H. T. Evans, jun., Inorg. Cliem., 1966, 5, 967.3Q A. G. Swallow, F. R. Ahmed, and W. H. Barnes, Acta Cryst., 1966, 21, 397.40 H. A. Eick and L. Kihlborg, Acta Chem. Scand., 1966,20,722.4l R. Eisenberg, E. I. Stiefel, R. C. Rosenberg, and H. B. Gray, J . Amer. Chem. SOC.,1966,&8,2874.A. Astrom, Acta Chem. Scand., 1966, 20, 969.G. M. Brown and L. A. Walker, Acta Cryst., 1966, 20, 220.44 L. R. Bateman, J. F. Blount, and L. F.Dahl, J. Amer. Chem. Soc., 1966,88,1082.*s J. M. Longo and P. Kierkegaard, Ado Chem. Scand., 1966,20, 72.46 H. Brusset, H. Gillier-Pandraud, and R. Mahe, Compt. vend., 1966, 285, C, 217696 CRYSTALLO QRAPHYthe network; the Nb-Nb distances are 3.22 and 3.60 8, with Nb-0 rang-ing from 1430-2.15 8. The lead atoms are situated at the apices of pyramidswith triangular bases of three oxygens; Pb-0 distances are about 2-60 8.A niobate and tantalate of antimony have been compared with the oxide.SbNbO,, SbTaO, and a-Sb204 are i~ostructural.~~ There is a considerabledistortion from ideal octahedral coordination of the NbV in SbNbO,; theSbXu is effectively five-co-ordinate.The electronic spectra of polynuclear subhalides of tantalum of generalformula Ta,Xl,,7H,0 have been explained in terms of a distorted poly-nucleus in which two tantalum atoms a t the apices of an elongated tetragonalbipyramid approach a valence of +3 while four tantalum atoms in theequator of the bipyramid approach a valence of +2.An X-ray structureanalysis 48 of Ta,C11,,7H20 crystals is consistent with this interpretation.The polynucleus combines with twelve chlorine atoms to form a Ta,Cl,,Z+complex ion which then combines with two chloride ions and four H20molecules to form a Ta,Cl14,4H20 unit. These units form layers whichalternate with the remaining water molecules. The alternation is irregular,apparently to maximise hydrogen bonding throughout the crystal.Group VIa.-In the structure of KCrsOs, CrO, octahedra and CrO,tetrahedra are arranged in layers by sharing corners.49 The structure ofCsCr30, is very similar, with the exception of the orientation of half thetetrahedra which are rotated, with a resulting doubling of the repeat distancenormal to the layers in this czesium-type structure.LiCr30s is built up ofstrings of (LiCr)O, octahedra and the strings are linked via CrO, tetrahedra.The analysis of a new polymorph of CrOOH shows it to be isostructuralwith InOOH. The chromium atoms have, of course, distorted octahedralc~-ordination.~O Two independent analyses of Cr( H,0),C1,C1,2H20 byMorosin 51 and by Dance and Freeman 52 show that the chromium ions areco-ordinated by two Cr-C1 distances of 2-29 A and four Cr-0 distances of2-00 A. Chloride ions and water molecules are linked together by a networkof hydrogen bonds.The results are identical within experimental error.Dance and Freeman point out that the chromium structure is isomorphouswith trans[NiCl,( OH2)J,2H,O and that the analogous cobalt complex isalso similar to [CrCl,( OH,)4]C1,2H20. Comparisons are made with thehydrocyanic acid derivatives.Confirmation of the presence of triangular groups of bonded molybdenumions in zinc rnolybdenum(rv) oxide, Zn2N0,O,, has been made;53 Mo-Mo dis-tances are 2.52 8, and the molybdenum ions have approximately octahedralco-ordination by oxygen atoms, with octahedral sharing edges. Mean Mo-0distances range from 1.93-2.13 A. The complex ion ([MOO( C2O,)H,0l2O2) 2-has a Me-Mo bond length of 2.54 Two octahedrally co-ordinated molyb-4 7 A.C. Skapski and D. Rogers, Chem. Comm., 1965, 611.48 R. D. Burbank, Inorg. Chem., 1966, 5, 1491.48 K. A. Wilhelmi, Chem. Comm., 1966, 437.51 B. Morosin, Acta Cryst., 1966, 21, 280.63 I. G. Dance and H. C. Freeman, lizorg. Chem., 1965, 4, 1555.63 G. B. Ansell and L. Katz, Acta Crysta., 1966, 21, 482.54 F. A. Cotton and S. M. Morehouse, Inorg. Chem., 1965, 4, 1377.A. N. Christensen, Inorg. Chem., 1966, 5, 1452GERLOCH AND MASON 697denums share an edge with double oxygen bridges. It is suggested that thediamagnetism arises directlyfrom metal-metal bonding rather than super-exchange wia the oxygens. Two other structures containing octahedrallyoxygen-co-ordinated molybdenum ions are represented by sodium andpotassium molybdenum bronzes.559 56 Sodium molybdenum bronze consistsof a trigonal distorted perovskite structure in which sodium ions are orderedin 1/6 of the voids between MOO, octahedra. In the potassium molybdenumbronze, K,.,,MoO,, a layer structure is built up from sub-units consisting often distorted octahedra sharing edges, sub-units being linked by corners.The octahedrally co-ordinated layers are joined solely by inter-layer potas-sium ions in 7- and 10-co-ordinate sites. The Kf sites are only fractionallyoccupied. An interesting structure is that of MoS,C,H6 (ref. 57) since theMo atoms have trigonal-prismatic co-ordination, as in Re(S,C,Ph,),. TheS-Mo-S angle is 83" and mean Mo-S bond length is 2.33 8.There have been two structure analyses of tungsten trioxide.A neutrondiffraction analysis of W03 shows 58 that the tungsten-oxygen bonds formzig-zag chains in three directions with W-0-W angles of 158" and 0-W-0angles of 166". Each tungsten has a distorted octahedral co-ordinationwith bond lengths ranging from 1-79-2-16 A. The sub-stoicheiometrictungsten trioxides, WO,. 98 and 1470,. 96, have significantly different structuresfrom tungsten trioxide it~e1f.j~ The W0,.9, a-structure corresponds toW,,O1,, units and at 1250" it probably contains W2,0,p units. Each unitcell of the two separate substoicheiometric trioxides contains two hexagonal-shaped ordered defects bisected by recurrent dislocation planes.Organornetallic compounds. Several papers have recently been concernedwith the structure of arenechromiurn tricarbonyls.In o-toluidinechrolniumtricarbonyl the carbon-chromium vectors point closely towards the benzenecarbon atoms which are ortho and paru to the NH, substituent. The generalconclusion is that configurations for substituted-benzenechromium tricar-bonyls directly reflect the electronic characteristics of ring substituents. Inphenanthrenechromium tricarbonyl and 9,I O-dihydrophenanthrenechromiumtricarbonyl the chromium bonds to a side ring.61 It appears that the bond-ing of the chromium to the arene merely causes a general lengthening ofcarbon-carbon bonds in the ring rather than additional bond length alterna-tion. Such a conclusion is, of course, consistent with our present views onbonding in dibenzenechromium and, for example, in hexamethylbenzene-chromium tricarbonyl.Another re-investigation of dibenzenechromium hasappeared. 6 2 The analysis of low-temperature counter data shows equalC-C bond lengths of 10417A and a mean GI€ distance of 0.93A. Theauthors claim that their results go some way, but not far enough, towardsfinally disproving the hypothesis of orientational disorder in the crystal.66 N. C. Stepenson, Acta Cryst., 1966, 20, 59.66 J. Graham and A. D. Wadsley, Acta Cryst., 1966, 20, 93.5 7 A. E. Smith, G. N. Schrauzer, V. P. Mayweg, and W. Heinrich, J. Awr, Chm.68 B. 0. Loopstra and P. Boldrbi, Acta: Cryst., 1966,21,158.6g E. Cebert and R. J. Ackermann, Inorg. Chem., 1966,5, 136.6o 0. L. Carter, A. T. McPhail, and G. A. Sim, Chem.C o r n . , 1906, 212.61 K. W. Muir, G. Ferguson, and G. A. Sim, Chem. Comrn., 1966, 465.E. Keulen and F. Jellinek, J . 0rgunometalli.c Chem., 1966,5,490.Sac., 1965, 87, 5798698 CRY STALLOQRAPHYAn X-ray analysis of the tricarbonylchromium derivative of the adductof diphenylketen and ethoxyacetylene 63 shows the chromium to be bondedto a cycloheptatriene ring which is approximately planar and shows bond-length alternation. The tetrahedral carbon of the cycloheptatriene and thechromium atom are on opposite sides of the six-carbon conjugated system.The average Cr-C distance is 2-23 8. In the 1 : 1 electron donor acceptorcomplex formed from tricarbonylchromiumanisole and 1,3,5-trinitrobenzene,the benzene rings of the two components are virtually parallel with per-pendicular distances from the aromatic carbon atoms of the anisole moleculeto the plane of the trinitrobenzene group 64 ranging from 3.34-3.50 8.Incyclopentadienyldinitrosylchromium chloride 65 the Cr-N-0 angles are bentby up to 10" and the interpretation of this bond angle is of an electronicrather than steric origin in much the same way as has been discussed for thecase of metal carbonyls by Kettle. The cyclopentadienyl ring is disordered.A particularly interesting structure is that of the HCr2(CO)lo- ion.66 Itis suggested that the Cr-H-Cr molecular system is stabilised by a three-centre one-electron-pair bond. While the hydrogen atom has not been found,the observed clwomium-chromium distance of 3.41 A implies, in a symmetri-cal situation, a chromium-hydrogen value of 1.70 A which is thought to beconsistent with other known metal-hydrogen bonds.The implication ofthe stereochemistry is that these monohydridic dimeric complexes cannot befurther protonated, in agreement with the non-isolation of any di-hydridicspecies.The ligand in tricarbonyl- 1,6-methanocyclodecapentaenechrornium isattached asymmetrically to the metal which is trans to the methylenebridge (2).67 The chromium is not equally bonded to all carbon atoms,______ _ _ ~~63 W. A. C. Brown, A. T. McPhail, and G. A. Sim, J . Chem. Eoc. ( B ) , 1966, 604.64 0. L. Carter, A. T. McPhail, and Gr. A. Sirn, J. Chem. SOC. (A), 1966, 822.e6 0. L. Carter, A. T. McPhail, and G. A. Sim, J . Chem. SOC.(A), 1966, 1095.66 L. B. Handy, P. M. Treichel, L. F. Dahl, and R. G. Hayter, J . Amer. Chem. Soc.,67 P. E. Baikie and 0. S. Mills, Chem. Comm., 1966, 683.1966,88, 366#ERLOCH AND MASON 699which form one ring. The carbene, methylmethoxycarbenetriphenylphos-phinechromium tetracarbonyl has a chromium-carbene distance of 2.04,significantly longer than the remaining chromium-carbon distance of1.84An X-ray analysis of z-cy clopentadienylperfluorethylmolybdenum tri-carbonyl6@ allows a direct comparison of molybdenum-alkyl and -perfluor-alkyl bond lengths. The Mo-fluoroalkyl carbon bond length is 2.288,0-12 less than the corresponding Mo-ethyl-carbon distance in the alkylcomplex. Abrahams and Ginsberg, in a new refinement ' 0 of the structureof bis-n-cyclopentadienylmolybdenum dihydride, suggest that the X-raydata contain no evidence for any short metal-hydrogen bond lengths.Group ma.-Several crystal structures of Tutton's salts have beendetermined.In manganese ammonium sulphate he~ahydrate,'~ the man-ganese ion is almost regularly octahedrally co-ordinated by water molecules,the average metal-oxygen distance being 2-18A. The structure is verysimilar to that of cadmium ammonium sulphate hexahydrate 7 1 where theaverage metal-oxygen distance is 2.28 A. Each molecule forms two hydrogenbonds ranging in length from 2-72-2432 8. The ammonium ion in all thesestructures is hydrogen-bonded to oxygen atoms of sulphate groups. X-rayand neutron refmement 72 of powder diffraction data of MnSO, shows ootta-hedral manganese and tetrahedral sulphur groups which are shared to givea very regular lattice.The structure of strontium permanganate trihydrate T 3 consists of Mn0,-anions, Sr2+ cations, and water molecules.Mn0,- groups have nearlytetrahedral symmetry (Mn-0 is 10605A) while the Sr2+ cations are SIX-rounded by seven oxygens and three water molecules. In potassium hem-chloromanganate(Iv), the least-squares analysis of the powder data, givesbdn-Cl, 2.276 and K-Cl, 3~4128.~4 Similar structures are observed forNE4+, Rb+, Cs+, and Et,N+ salts. The spectrum of the K+ salt is discussed.An example of a one-dimensional co-ordination polymer is afforded bythe structure of manganese(=) croconate.75 An infinite chain structure ofC,O,Mn(H,O), is observed in which the maiiganese(n) is co-ordinated to twoadjacent oxygen atoms of one croconate ring, one oxygen atom of anotherand three water molecules to complete a distorted octahedron.The atruc-ture is similar to the zinc(=) and copper@) croconates. Manganese is againoctahedrally co-ordinated in K3Mn(CN),N0,2H,0, by- five cyanide and onenitrosyl groups.76 Mn-C(N) distances range from 1.95-1-99 A; Mn-N(O)bond length is 1-65A.The crystal structure analysis of a double complex of manganese with68 0. S. Milla and A. D. Rodhouse, Chem. Contm., 1966, 814.6Q M. R. Churchill and if. P. Fennessey, Chem. Comm., 1966, 695.' 0 S. C. Abraham and A. P. Ginsberg, Inorg. Chem., 1966,5,500.H. Montgomery and E. C. Linga.felter, Acta Cryst., 1966,20,728; H.Montgomery72 G. Will, B. C. Frazer, and D. E. Cox, Acta Cryst., 1965, 19, 854.73 A. Ferrari, A. Braibanti, G. Bigliardi, and A. M. M. Lanfredi, -4cta Cryst., 1966,7 4 P. C. Moews, jun., Inorg. Chem., 1966, 5, 5 .76 M. D. Gliok and L. F. Dahl, Inorg. Chetn., 196G, 5, 389.76 A. Tullberg and N.-G. Vannerberg, Acta Chew. Scad., 1966, 20, 1180.R. V. Chastain, and E. C. Lingafelter, &id., p. 731.21, 681.700 CRYSTALLOGRAPHYphthalocyanato- and pyridine ligands has been completed.' A dimericmolecule with octahedral co-ordination of the manganese atoms is formedby an essentially linear Mn-0-Mn bridge in which the Mn-0 distance is1.71 8. The phthalocyanine rings, perpendicular to the bridge vector, areflat and parallel with Mk-N bond lengths of 1.97 A.The octahedra arecompleted, at both ends of the dimer, by pyridine ligands (Mn-N = 2.15 A).In technetium(rv) chloride,78 distorted octahedral units of compositionTcCl, are linked to form polymeric chains, each octahedron sharing oneedge with each of two adjacent octahedra. The building unit of the chainis a Tc&& unit made up of two TcCl, planar asymmetric parts related toeach other by a glide plane. Three pairs of chemically distinct Tc-Cl bondsexist whose mean lengths are 2.24, 2.38, and 2-49B.An example of the trirhenium(m) cluster is to be found in the structuralanalysis 79 of Re,Br,( AsO,),( dimethylsulphoxide),. Analysis of the infraredspectrum shows that two tridentate arsenate ions have replaced the six axialhalide ions in the Re,&, molecule to form a cage which incorporates thecluster.The solvent (DMSO) molecules are thought to occupy equatorialsites in the cluster. The molecular structure of tetraphenylarsonium-oxotetrabromoacetonitrilerhenate(v) shows rhenium with an approximateC,, co-ordination symmetry. Average Re-Br distance is 2.48; Re-0, 1.73,and Re-N, 2.31 8. The Re-0 bond is shorter than would be expected for anRe-0 double-bond, implying some triple-bond character. The Re-Re bondin Re,Cl,(DTH), (where DTH is 2,5-dithiahexane) is 2.29 A, intermediatebetween those observed for bond orders of two and threes1 The moleculeconsists of ReCl,,Re(DTH),Cl in which the ReC1, and ReS, groups are stag-gered with respect to one another.Another example of trigonal prismatic co-ordination has been found intris(cis-l ,2-diphenylethene-l,2-dithiolato)rhenium.82 Rhenium is surroundedby six equidistant sulphur atoms in a trigonal prismatic co-ordination, thesides of the prism being nearly perfect squares with an average edge of3-04 8.The phenyl rings are twisted out of the planes of the five-memberedchelate rings and appear not to be conjugated with them. The co-ordinationsymmetry is D3h but the overall molecular symmetry is C3.The length of metal-hydrogen bonds inorganometallic molecules has been discussed 8, with particular reference tothe broad line nuclear magnetic resonance analysis of the manganese-hydrogen bond lengths in HMn(CO),. The Mn-H distance is 1-28 & 0.01 8,which is much shorter than the sum of the covalent radii.In triphenyltinmanganese pentacarbonyl,84 the tin is essentially tetra-hedral and the manganese octahedral. Mean Mn-Sn distance is 2.67&Organometallic compounds.77 L.H. Vogt, jun., A. Zalkin, and D. H. Templeton, Science, 1966, 151, 669.78 M. Elder and B. R. Penfold, Inorg. Chem., 1966, 5 , 1197.7s F. A. Cotton and S. J. Lippard, J. Amer. Chem. SOC., 1966, $8, 1882.8* F. A. Cotton and S. J. Lippard, Inorg. Chem., 1966, 5, 416.*1 M. J. Bennett, F. A. Cotton, and R. A. Walton, J. Amer. Chem. SOC., 1966, 88,a2 R. Eisenberg and J. A. Ibers, Inorg. Chem., 1966, 5, 411.$8 T. C. Farrar, W. Ryan, A. Davison, and J. W. Faller, J . Amer. Chem. SOC., 1966,84 H. P. Weber and It. F. Bryan, Chem.Comm., 1966, 443.3866.88,184GERLOCH AND MASON 701intermediate in length between those found for triphenyltin, triphenyl-phosphinemanganese tetracarbonyl and diphenyltinmanganese bis-penta-carbonyl. The mean Mi-C distance is 1-76A and the Sn-C is 2-158.Another analysis has been made of a transition-metal carborane com-plex (3). In (B,C2HII)Re(CO),Cs, the rhenium atom occupies an apicalposition of an icosahedron of boron and carbon, and, on the other side,occupies the apex of a trigonal pyramid whose base is three carbonyls. Inthe icosahedron, the two carbon atoms are adjacent to each other and tothe rhenium. The mean rhenium(=)-carbon (carbonyl) distance is 1.77 Athe other rhenium-carbon distances range from 1.76-1.79 8; the Re-Bdistances average 1-77FeCI(4) ‘Group WlI.-Iron, ruthenium, osmium.The effect of high pressure onthe lattice parameters of cc-Fe203 and Cr,03 has been investigated 86 andcompared with results for A120,. Cr,O, exhibits a compressibility whichdecreases markedly with increasing pressure while M,O, has a compressi-bility almost independent of pressure. The compressibility of cc-Fe,O,actually increases with pressure, in the low pressure region, which may beassociated with the unusual behaviour observed in Mossbauer studies.In H,@$“,], the E”e(CN),4- ions consist of regular octahedra with amean iron-carbon bond length of 1.89 8.8’ There are two kinds of hydrogenbond, one almost symmetrical in which the N-H bond lengths are 1.23 and1-45 A and the sec6nd asymmetric in which two N-H distances are 1-81 and1-11 A.Some interesting comparisons between the motions of water mole-cules in potassium ferrocyanide trihydrate, water, and ice have been madeby neutron scattering techniques.88 The results show no significant changein the average rotational or translational freedom of H20 molecules in theferrocyanide complex at or near its ferroelectric transition. Moreover, boththe total cross-section and inelastic scattering results indicate a greaterfreedom of motion of H20 molecules in the complex lattice than in eitherwater or ice. In addition, a decrease in the total cross-section of H,O andA. Zslkin, T. E. Hopkins, and D. H. Templeton, Inorg. Chem., 1966, 5, 1189.J. J. Rush, P. S. Leung, and T.I. Taylor, J . Chem. Phys., 1966,45, 1312.8 6 G. K. Lewis, jun., and H. G. Drickamer, J . Chem. Phys., 1966, 45, 224.87 M. Pierrot, R. Kern, and R. Weiss, Acta Cryst., 1966, 20, 425702 CRY STALLOQRAPHYin its variation with neubron wavelength is observed at the water-ice transi-tion, indicating a significant change in the frequency distribution.Structural analyses of ludlamite, Fe,(PO,),,4€€,0, have been carried outat 4.2" and 298" The neutron diffraction analysis a t 4 . 2 " ~ showsthat the octahedral distances are 2.019-2-317, the average being 2.154 8.The phosphates are very nearly regular tetrahedra, P-0 distances being1*521-1*553 8. Average 0-H distance is 1-00 A and the shortest hydrogenbond is 2-5468. The magnetic unit cell coincides with the nuclear cell.The spins on each linear triad of iron atoms, separated by 3.267& areferromagnetically coupled and essentially parallel.Triad spin componentsin the ac-plane are related by the screw axis or glide plane operations and areantiferromagnetically coupled, while those parallel to the b-axis are ferro-magnetically coupled. At 298 "K the iron-oxygen distances range from2.016-2.362, the average being 2-156A. The P-0 distances range from1.536-1.549, the 0-H bond length is 0437 and 0-H 0 is 2.541 A.The structure of the seven-co-ordinate trans- 1,2-diaminocyclohexane-NN'-tetra-acetatoaquoferrate(m) ion (4) has been determh~ed.~l It is stereo-chemically similar to the anionic ethylenedliaminetetra-acetato-chelates ofiron(m) and manganese(@.All three are sexadentate seven-co-ordinatemonoaquo-complexes in which the constraints on the formation of complexring systems are of primary importance.The configuration of ferrichrome-A tetrahydrate has been determinedtogether with an absolute configuration investigation by anomalous disper-sion meth0ds.~2 The molecule contains a hexapeptide ring with the amino-acid sequence : -om-om-orn-ser-ser-gly-, with a tram conformation a t eachpeptide link. The iron atom is bound by three hydroxamate rings in theconfiguration of a left-handed propeller. There are two hydrogen bondswithin the molecule.Di-chlor o - 2,2', 2"- t erp yridineiron ( II) is isomorphous with dichlorot erp yridine -z ~ ~ c ( I I ) ~ ~ showing that the iron is five-co-ordinate with a distorted squarepyramidal ge0metry.1~~ Of considerable interest, from a magnetic point ofview, are a series of complexes [Fe(S,C*NR,),X] where X = C1, Br, or I, andR = Me, Et, Pri, and Bu.The effective moment a t room temperature is3-98 B.M. which has been ascribed to a spin state of 3/2. The molecularstructure 94 of monochlorobis(diethyldlithiocarbamato)iron(m) shows a dis-torted square pyramidal geometry with Fe-Cl 2-27A and average Fe-S2-32 .&. A further five-co-ordinate complex of iron@) with intsresthgmagnetic properties is afforded by NN'-bis-salicylidene-ethylenediamine-iron(m) chloride. This complex has been isolated both as a pentaco-ordinabmonomer and as a hexaco-ordinate dimer and structural analyses of bothSeveral five-co-ordinate iron complexes have been investigated.Is S.C. Abrahams, J. Chem. Phys., 1966,44, 2230.so S. C. Abraham and J. L. Bematein, J . Chem. Phys., 1966, 44,2223.91 G. H. Cohen and J. L. Hoard, J . Amer. Chem. SOC., 1966, 88, 3228.g 2 A. Zalkin, J. D. Forrester, and D. H. Templeton, J . Amer. Chem. SOC., 1966, 88,D3 D. J. Robinson and C. H. L. Kennsrd, AustraE. J . Chem., 1966, 19, 1285.Q* B. F. Hoskins, R. L. Martin, and A. H. White, Nature, 1966,211,627; M. Gerlooh,1810.J. Lewis, F. E. Mabbs, and A. Richards, ibid., 212, 809GERLOCH AND MASON 703forms have been completed. The monomer has a square pyramidal geometrywith the apical Fe-C1 bond length being 2-24 ,k and, like the thiocarbamatestructure above, has the metal atom about 0 .5 8 above the plane of thedonor atoms. The complex exhibits a large and very temperature-dependentmagnetic anisotropy. The dimer is formed by the formation of two oxygenbridges, one from each &hi€€ base, to give an asymmetric arrangement withFe-0 distances of 1-98 and 2.188.Tetragonal ruthenium dioxide contains no cluster~.~5 Two types of Ru-0distances of length 1.917 and 1-999 ,k occur, with the shortest Ru-Ru dis-tance 3-11 8. The question arises as to why this complex has a low suscepti-bility, as large spin-orbit coupling will not explain the fact. The aquopenta-chlororuthenate ion consists of octahedrally co-ordinated ruthenium@) ;Ru-0 and Ru-C1 distances average 2.10 and 2.34A, respecti~ely.~~ Intetraphenylarsonium cis-diaquotetrachlororuthenate mon0hydrate,~7 theruthenium octahedra are composed of four chlorine ions and two water moIe-cules, the waters being in cis positions.Average Ru-0 and Ru-C1 distancesare 2-12 and 2.34A. The tetraphenylarsonium ion has an unsymmetrimlconfiguration with an average As-C bond length of 1-91 8. The ruthenium(=)ion is also six-co-ordinate in tris(diphenylarsinopheny1)arsineruthenium di-bromide.9* The atructural analysis of nitrosylruthenium tris(NN-diethyl-dithiocarbamate) shows the molecule to contain a monodentate dithio-carbamate In both [Ru(NO)(S,CNEt&] and [Ru(S,CNEt,),], theruthenium atoms have octahedral co-ordination, but in the latter this isdistorted by the requirement of the four-membered ring. The bond angleS-Ru-S is approximately 73".The Ru-S distances are essentially equalat 2-39 8. In the nitrosyl complex the N-0 distance of 1.17 A indicatesthat the nitrosyl ligand can be considered as NO+: the nitrosyl groups arein a cis position with respect to the monodentate dithiocarbamate.Organometallic compounrls. The bond lengths in iron pentacarbonyl haveagain been discussed.lOO Donohue and Caron suggest that Davis andHansen's data prove that the axial bonds are longer, rather than shorter,than the equatorial values, but not significantly so. The electron diffractiondata by Donohue and Caron gave axial bonds 0.0458 shorter than theequatorial values. Perhaps the most significant analysis in this general area,is the final and successful analysis of the structures of dodecacarbonyltri-ironand dodecacarbonyltetracobalt by Wei and Dahl.101 The structure ofdodecacarbonyltri-iron is finally confirmed as that which was suggested onthe basis of the X-ray analysis of HFe,(CO),l- ion. The structure may beunderstood as being formed by the insertion of a cis-Fe(CO), group at oneof three bridging carbonyl positions of Fe,(CO),.The twelve carbonyl96 F. A. Cotton and J. T. Magus, Inorg. Chem., 1966,5, 317.O 6 T. E. Hopkins, A. Zalkin, D. H. Templeton, and M. G. Adamson, Inorg. Chcm.,O 7 T. E. Hopkins, A. Zalkin, D. H. Templeton, and M. G;. Adamson, Inorg. Chum.,O 8 R. H. B. Mais, and H. M. Powell, J . Chem. SOC., 1965, 7471.A. Dormmicano, A. Vaciago, L. Zambonelli, P. L. Loader, and L. M. Venami,1966, 5, 1431.1966,5, 1427.Chem.Comrn., 1966,476.loo J. Donohue and A. Caron, J . Php. Chem., 1966, 70, 603.lol C. H. Wei and L. F. Dahl, J . Arner. Chem. SOC., 1966,88, 1821To4 CRYSTALLO QRAPHYgroups are approximately disposed towards the vertices of an icosahedron.Two ohemically equivalent Fe-Fe distances of 2.69 and 2.68 occur with a,third shorter one of 2.558. CO,(CO)~~ has approximately C3v symmetry,consisting of an apical Co(CO), group co-ordinated by cobalt-cobalt bondsto a Co,(CO), fragment containing three identical Co(CO), groups situateda t the corners of an equilateral triangle. The cobalt atoms are W e d toone another by both symmetrical bridging carbonyl groups and cobalt-cobaltbonds. The six independent cobalt-cobalt bond lengths are equivalentwithin experimental error (2-49A).The molecular structure of a tin-ironcarbonyl cluster lo2 shows the tin to have a tetragonally distorted tetra-hedral stereochemistry, with two different pairs of iron-iron distances of2.87 and 4.65 8. The Sn-Fe bond length is 2.53 8. Each iron can be thoughtof as having approximately distorted octahedral co-ordination with onePe-Sn bond, one Fe-Fe bond and four Fe-(CO) bonds. The molecular con-m a t i o n of Fe,(CO)l, is confirmed in detail by a structural analysis lo3 ofFe,(CO)llPPh,. In the phosphine complex, the isosceles triangle of ironatoms has sides of 2-70 and 2-55 8; Fe-P is 2.25 8. Two bridging carbonylsare asymmetric, the longer Fe-C distances averaging 1.98 and the shorter,1.81 A.The symmetry is consistent with the fact that the bridged Fe-Fedistances are greater than the 2.94 found in Fe,(CO),(C,H,), and 2*46Ain Fe,(CO),.A new type of iron-acetylene interaction is shown in the structure of anawe-nonacarbonyltri-iron complex.lo4 The three iron atoms are arrangedin an isosceles triangle, two Fe-Fe distances averaging 2.49 and one Fe-Fe2.68 8. The diphenylacetylene group lies above the plane of the three irons;one acetylene carbon is bonded to all three irons, the other to two symmetryrelated irons.In [PhCsFe(CO),],, the two crystallographically independent moleculesin the asymmetric unit are distorted by torsional deformation about thebridging ethylinic bond.105 The important point is that each of the mole-cules is distorted in a slightly different way, which may be related to thecrystal structure.Two independent analyses 1069 107 have been made of thestructure of (C,H,FeS)4. The molecule consists of an elongated tetrahedronof iron atoms with a sulphur atom above each face and a cyclopentadienylring projecting from each corner. The molecular symmetry is approximatelyDza; Fe-Fe bond lengths are 2-64 and 2.62 with four independent Fe-S bondsaveraging 2.206 and a further three averaging 2*26A.The problem of the n.m.r. equivalence of the protons in the non-sandwichbonded cyclopentadienyl group of n- (C,H,)Fe(CO),-C,H, has been investi-gated lo* by X-rays and low-temperature n.m.r. methods. The n.m.r. spectralo8 J. D. Cotton, J. Duckworth, S.A. R. Knox, P. F. Lindley, I. Paul, F. Gt. A.Stone, and P. Woodward, Chem. Comm., 1966,263.108 D. J. D a b and R. A. Jacobson, Chem. Comm., 1966,496.1 O 4 J. F. Blount, L. F. Dahl, C. Hoogzand, and W. Hubel, J . Amer. Chem. SOC., 1966,88, 292.106 R. F. Bryan and H. P. Weber, Chem. Comm., 1966, 329.106 R. A. Schunn, C. J. Fritchie, jun., and C. T. Prewitt, Inorg. Chem., 1966,15, 892.lo' C. H. Wei, G. R..Wilkes, P. M. Treichel, and L. F. Dahl, I w g . Chem., 1966,6,m.1oaM. J. Bennett, jun., F. A. Cotton, A. Davison, J. W. Faller, S. J. Lippard, and8. M. Morehouse, J. Amer. Chem. SOC., 1966, 88, 4371GLCRLOCH AND MASON 706indicate that the molecular configuration of greatest stability in solution issimilar to that in the crystal, which contains one a-bonded cyclopentadienylring.Mean distances are: Fe-C, (a-Cp) 2.11; Fe-C, (z-Cp) 2-06 andFe-C, (CO) 1-70 A. In diferrocenyl ketone,log each iron atom is sandwichedbetween two five-membered rings which are planar, parallel, and essentiallyin an eclipsed conformation. The ferrocenyl groups are rotated 17" withrespect to the carbonyl. In bridged ferrocenes, the degree of inclinationbetween the two cyclopentadienyl rings has been commented on in thestructural analysis of 1,l' ; 3,3'-bi~(trimethylene)ferrocene.~~* In the twocrystallographically independent molecules, the angle of tilt between therings is 9", the two cyclopentadienyl rings being in the eclipsed conforma-tion. The molecular structure of ferrocene itself has been examined in thegas phase at 140" by electron diEraction.lll In contrast to the crystallinestate, the rings are eclipsed, the barrier to internal rotation from D5,, sym-metry being estimated at about 1.1 kcal./mole.Bond lengths are; Fe-C,2.058; C-C, 1.431, and C-H, 1-12 8. The hydrogen atoms appear to bedisplaced towards the metal atom, the C-H bonds making an angle ofabout 5" with respect to the rings. A preliminary investigation of Mn(C,H,),indicates the lack of any such hydrogen atom displacement and brings intoquestion the validity of the proposals relating to ferrocene.In a complex of cyclo-octatetraene and iron pentacarbonyl,l12 the bond-ing of the cyclo-octatetraene to the iron can be thought of as proceedingwia the bonding of a n-ally1 fragment.The suggested bonding scheme in-volves two three-centre bonds each containing two electrons extending overthe two iron atoms and a carbon atom, and an iron-iron bond to achievean inert gas configuration. The stabilisation of an ally1 fragment in a cyclicligand is also illustrated by the structural analysis 113 of C10H,Fe2(CO)6.One Fe(CO), group is symmetrically bonded to all carbon atoms in the five-membered ring of the azulene system, the other iron is bonded to threecarbonyl groups and associated with only three atoms of the seven-memberedring (5). Iron-iron bond lengths are 2.78 d, and the azulene ligand is nolonger strictly planar. The structure of a vinyliron compound is shownin (6). The molecule is formulat,ed as dicarbonyl-1 -methoxycarbonyl-2-phenyl-2-n-2',4'-dimethoxycarbonyl-3',5- 1 '-cyclopentadienyloxy-a-vinyliron and its preparation and properties are discussed at length.l14 Anovel structure ( 7 ) is displayed by diphenylvinylideneoctacarbonyldi-iron 11sin which two Fe(CO), groups are bridged by a single Ph2CC ligand.Co-ordination round each iron is a distorted trigonal bipyramid with an Fe-Fedistance of 2.64 8. The ligand may be regarded as a bridging carbene. Irontetracarbonyl fragments are co-ordinated exclusively to the central bond oflo# J. Trotter and A. C. Macdonald, Acta Cryst., 1966, 21, 359.110 I. C. Paul, Chem. Comm., 1966, 377.ll1 R. K. Bohn and A. Haaland, J . Organonaetallic Chern., 1966,5, 470.11* E. B. Fleischer, A. L. Stone, R. B. K. Dewar, J. D. Wright, C.E. Keller, and R.Pettit, J . Amer. Chem. SOC., 1966, 88, 3158.llS M. R. Churchill, Chm. Comm., 1966, 450.114 L. F. Dahl, R. J. Doedens, W. Hiibel, and J. Nielsen, J . Amp. Chem. Soc., 1966,88, 446.0. S . Mi.& and A. D. Redhouse, Chem. Cmm., 1966, 444706 CRYSTALLOGRAPHYcoPhbthe cumulated double-bond system in a cumulene-metal-carbonyl complex.1'6Once again, the metal co-ordination is trigonal bipyramidal. A similar metalstereochemistry is found in the structure of racemic Fe( CO),-fumaricacid.117 The question of the conformation of groups attached to co-ordinatedolefins is examined. The carbonyl groups are bent away from the carbonsof the co-ordinated olefin in a sense to mix more pcharacter into the metal-carbon bond.The structures of two nitrogen-containing organometallic complexeswhich have been determined are the reaction product of iron enneacarbonylwith the Schiff base formed from p-toluidine and benzaldehyde and from116 D.Bright and 0. S. Milk, Ohem. Comm., 1966, 211.11' P. Corradini, C. Pedone, and A. Sirigu, Chm. Comm., 1966,341QERLOCH AND MASON 707azobenzene.ll8 In the former, the nitrogen symmetrically bridges two ironat>oms separated by 2-3 A whereas, in the latter, two nitrogen atoms bridgetwo Fe(CO), groups which are themselves arranged in an eclipsedconfiguration.There have been two further structural analyses which illustrate the per-turbation of a ligand with an alternating single- and double-bond system bya co-ordinating metal. The molecule, tricarbonyltetrakis(trifluoromethy1)-cyclopentadienoneiron 119 contains a substituted cyclopentadienone ringwhich is non-planar.The formation of localised cr- and n-bonds between themetal ion and the cyclic ligand contributes substantially to tbe bonding.A detailed discussion of the molecular geometry is given in terms of bothvalence bond and molecular orbital theory. A complex of iron tricarbonylwith vitamin A-aldehyde,lZ* besides establishing the conformation of thevitamin, also shows that the bond length alternation in the free polyenechain is perturbed on complexing with the -Fe(CO), group (8).( 8 ) (‘9)Group VIPI.--Cobalt, rhodium, iridium. One of the more significantcobalt complexes of which the structure has been determined is a peroxo-bridged dicobslt cation (9).lZ1 The structure consists of a cobalt-O-O-cobalt11* P. E.Bailie and 0. S. Mills, Chem. Comm., 1966, 707.ll0 N. A. Bailey and R. Mason, Ada Cryst., 1966, 21, 652.120 A. J. Birch, H. Fitton, R. Mason, G. B. Robertson, and J. E. Stangroom, Chem.121 W. P. Schaefer acd R. E. Marsh, J . Amer. Chem. SOC., 1966, 88, 179.Comrn., 1966, 613708 CRYSTALLOGRAPHYextended chain, the co-ordinated 0-0 bond length being 1*315A, onlyslightly longer than in the metal superoxides. This structure is almostcertainly representative of peroxide complexes of metals whose other ligandsare relatively weak, i.e., it is not a n-bonded oxygen complex. In the struc-ture of K,BaCo(NO,),, the cobalt is octahedral, with a mean Co-N bondlength of 1.98 Cobalt occupies a site of 8, symmetry and the nitriteion is not significantly distorted from that which one finds in sodium nitrite.The nitrite groups are monodentate.A continuous monitor of the lattice dimensions of CoC1,,2H20 has beenmade from 5-298"~.A small anomaly was found in the b lattice parameternear the N6el temperature. Unit cell dimensions contract anisotropicallyby up to 1% as the temperature is lowered, but the fractional atomic co-ordinates of the 5°K structure differ by only a maximum of 4a's from the2 9 8 " ~ structure. A detailed description of the cryostat arrangement usedis also given.123Cobalt is octahedrally co-ordinated with the bidentate ligand phenan-throline in [CoCl,phen2]+C1-; Co-C1 bond lengths are 2-23 and 2.26 g.124The phenant,hroline groups are cis to one another, Co-N (basal) bond lengthsaveraging 2.00 and axial Co-N 1.96 A.The axial Co-N bonds are, of course,trans to one another, while the basal ones are trans to chlorine atoms.A number of cobalt complexes have been determined which are importantin deciding the conformation of saturated ligands. In tris-[ (-)-propylene-diaminelcobalt (m) bromide, the complex ion has a three-fold axis, thecobalt-propylenediamine rings being puckered with the methyl carbon atomsequatorial.125 The absolute configuration has been determined using stand-ard Bijvoet methods. The CH-CH, bond in the chelate ring is nearlyparallel to the C,-axis of the complex and corresponds to the " lel " form.The absolute coniiguration of the (+)-cis-dinitrobis-( -)-propylenediamine-cobalt(m) ion has been determined,126 in which the cobalt ions are surroundedby a slightly distorted octahedron of nitrogen atoms.Co-N distances are1.87-2.018; the nitro-groups are in cis positions each being approximatelycoplanar with the cobalt atoms and with their planes approximately perpen-dicular Bo one another. The methyl groups of the proplyenediamine ligandsare in trans positions to one another while they occupy cis positions in theI,-( -)-tris-( -)-propylenediaminecobalt(m) ion. The conformation of thechelate rings as well as the absolute configuration about the cobalt atom issimilar to that found in L-( -)-tris-( -)-propylenediaminecobalt(m) ion inthat the chelate rings have the K-conformation with equatorial methylgroups, and the absolute configuration of the complex ion may be describedas " L ".A correlation is made with circular dichroism curves. Cobalt isagain octahedral in ~-[Coen,(~-glutamate)]ClO~.~~~ Via an intramolecular122 J. A. Bertrand and D. A. Carpenter, Inorg. Chem., 1966,5,614.128 B. Moroain, J. Chem. Phys., 1966, 44, 252.114 A. V. Ablov. A. Yu. Kon, and T. I. Mabovskii, Doklady Akad. Nauk S.S.S.R.,186 H. Iwaski and Y. Saito, Bull. Chem. SOC. Japan, 1966, 39, 92.G. A. Bsrclay, E. Goldschmied, N. C. Stephenson, and A. M. Sargeson, CireSn.187 J. H. Dunlop, R. D. Gillard, N. C. Payne, and G. B. Robertson, Chm. Cormn.,1966,167, 1051.C m . , 1966, 640.1966, 874GERLOCH AND MASON 709hydrogen bond the polar side arm of the L-glutamate ion interacts with theN-H group of an ethylenediamine chelate ring.The known absolute con-figuration of the asymmetric carbon atom in the L-glutamate chelate ringenables the fixing of the absolute configuration of the whole molecule whichis then D-[ Co ( en)2( ~-glut)]ClO,.A comparison of the dichlorides of hexamminecobalt(n) and the tri-iodideof hexamminecobalt(m) shows that the cobalt@)-nitrogen distance is2-11 A, cobalt(m)-nitrogen is 1-96 A.128 The glycylglycine ligand has beenshown to be terdentate in the structure of a bisglycylglycinatecobalt(m)c0rnplex.12~ The absolute configuration of a-( +)-tris-L-alaninatocobalt (III)has been determined.l30 The structure of an acetylacetonatocobalt (n)complex shows 131 that the molecule is a centro-symmetric dimer, similar instructure to the central fragment of the bis( acety1acetonato)cobalt tetramerbut with one bridge replaced by two molecules of water. The formation of adimeric structure is also shown in the structure of bis-cis-l,2-bis(trifluoro-methyl) et hylene- 1,2 - dithiolat e co b alt .32 Co balt-sulphur bonds are 2 - 14 8within the " monomer " with longer (2.38 A) bonds linking the two monomerstogether.The structure of tetraphenylarsonium tetrakis(trifluoroacetato)cobalt-ate(rr) 133 can be described essentially as a tetrahedralcobalt(n) complex inwhich the substituted acetate ligand is effectively unidentate.A number of five-co-ordinate complexes of cobalt(n) have been reported.In dibromotris(dipheny1phosphine)cobalt (n) two bromide and three phos-phorus atoms describe a trigonal bipyramid about the cobalt, the two phos-phorus atoms being in axial p0sitions.13~ The co-ordination 135 of thecobalt(n) chloride with N-methylated diethylenetriamine is such that thesyrnmetry of the co-ordination around the cobalt ion is neither clearlytrigonal bipyramidal nor square pra(mida1.The Co-Cl distances are 2-28and 2.33 A; Co-N bond lengths are 2.11-2.30 8. Steric repulsions appearto play an important part in determining the distribution of ligands aboutCiaM. T. Barnet, B. M. Craven, and H. C. Freeman, Chern. Comm., 1966, 307.laB R. D. Gillard, E. D. McKenzie, R. Mason, and G. B. Robertson, Nature, 1966,130 M. Q. B.Drew, J. H. Dunlop, R. D. Gillard, and D. Rogers, Chern. Cmm., 1966,209,1347.42.F. A. Cotton and R. C. Elder, I w g . Chem., 1966,5, 423.J. H. Enemark and W. N. Lipscomb, I w g . Chern., 1965,4, 172913s J. G. Bergman, jun., and F. A. Cotton, Inorg. Chern., 1966, 5, 1420.134 J. A. Bertram and D. L. Plymale, I w g . Chem., 1966, 5, 879.ls6 M. Di Vaira and P. L. Orioli, Chern. Cmm., 1965, 590710 CRYSTALLOGRAPHYthe cobalt atom. Bis(N-methylsalicylaldiminato)cobalt(n) 136 is isomor-phous with the Zn(rr) complex, and the structure consists of dimers with Cisymmetry in which the metal is five-co-ordinate. The co-ordination s pmetry is distorted trigonal bipyramidal. Square pyramidal co-ordinationof cobalt(n) is shown in the structure (10) of Co(paphy)Cl, 13’ ‘ paphy ’ isthe ligand pyridine-2-aldehyde-2’-pyridylhydrazone, which has three nitro-gen donor-atoms arranged in a manner similar to those in terpyridine).Themetal ion is 0.4 out of the basal plane in a sense towards the apical chlorineatom. The apical Co-C1 bond length is 2-33, only 0.05 A longer than the basalone. Isomorphism with Co-paphy)Br, and with halogeno-2,2‘,2”-terpyridylcomplexes of Mn, Co, Ni, Cu, and Zn (and, 8s referred to previously, of Fe)indicates that these complexes should be similarly described.13*Eight-co-ordination of the cobalt(n) ion is shown in the structure oftetraphenylarsoniumtetranitratocobaltate (n) . 139 Four bidentate nitrategroups surround the cobalt ion with a point symmetry reported as Iza butmay be idealized as Th.The eight Co-0 bonds can be divided into two setsof four, the shorter ones averaging 2.08 A and the four longer ones in pairsof 2.36 and 2.54 A, although the significance of these differences is open tosome doubt.Organometallic Compounds. In bis(tricoba1t enneacarbony1)acetone (1 I),two trinuclear cobalt fragments are joined together but not by a bridginglS6 P. L. Orioli, M. Di Vaire, and L. Sacconi, Inorg. Chem., 1966, 5, 400.Is’ M. Gerloch, J . Chem. Soc. (A), 1966, 1317.lS8 I. G. Dance, M. Gerloch, J. Lewis, F. S. Stephens, and F. Lions, Nature, 1966,13@ J. G. Bergman, jun., and F. A. Cotton, Inorg. Chem., 1966, 5, 1208.210, 298GERLOCH AND XASON 711carbonyl.140 Cobalt-cobalt bond lengths are 2.47 d, Co-C (carbonyl) 1.81 Aand Co-C (acetone) 1-92 8.The cyclic ligand peduorocyclopentadienebridges a Co( CO), and Co(CO), fragment in perfluorocyclopentadenedicobaltheptacarbonyl (12). The Co(CO), fragment is bonded directly by a a-bondto the ring while the Co(CO), group is bonded to an ally1 moiety. Therelationship of this structure to other substituted butadiene complexes isdiscussed. 141The stereochemistry of the rhodium atom in trans-bis(tripheny1phos-phine)thiocarbonylrhodium(I) chloride is square planar, with a slight dis-tortion.142 The two triphenylphosphine groups are nearly eclipsed and thsthiocarbonyl ligand is almost linear. The CS bond length is slightly shorterthan in CS,; Rh-C is 1.79 8 as compared with 1431 8 in the tris(tripheny1-phosphine)carbonylrhodium gydride. An interesting trimeric rhodiumstructure reported is that of n-cyclopentadienylcarbonylrho~~m.~~~ Withinexperimental error the trimer consists of an equilateral triangle of rhodiumatoms in which each pair of atoms is symmetrically bridged by a carbonylgroup.All carbonyl groups are displaced to one side of this metal triangleand each cyclopentadienyl ring is associated exclusively with one rhodiumatom. The Rh-Rh distance is 2.62 8. The nature of the bonding of transi-tion metals to cyclic organic ligands is again illustrated by the novel structureof mcyclopentadienylhexakis( trifluoromet,hyl)benzenerhodium The plan-arity of the substituted benzene ring is lost, the ligand being bent by 48".The bonding to the metal may be formally represented as of a u-n type, butthis is better considered quantitatively, however, by molecular-orbitaltheory.140 G.Allegra, E. M. Peronaci, and R. Ercoli, Chem. Comm., 1966, 549.141 P. B. Hitchcock and R. Mason, Chem. Comrn., 1966, 503.Ira J. L. DeBoer, D. Rogers, A. C. Skapski, and P. G. H. Troughton, Chem. Comm.,lP3 0. S. Mills and E. F. Paulus, Chem. Comm., 1966, 815.144 M. R. Churchill and R. Mason, Proc. Roy. SOC., 1966, A, 292, 61.1966, 756712 CRYSTALLOGRAPHYIn chlorocarbonyl( sulphur dioxide) bis (tripheny1phosphine)iridiu.m ( 13),the co-ordination of the iridium is that of a tetragonal pyramid with car-bonyl, chlorine, and trans-phosphines in the base and the SO, group at theapex.145 Once more the square pyramidal co-ordination is distorted so thatthe iridium atom is displaced by 0.21 8 towards t.he apical sulphur.TheIr-8 bond length of 2-49 A is very long and the dimensions of the SO, groupare not significantly different from those found in solid SO,. The geometryof the sulphur dioxide complex is different from that of the analogousoxygen complex Ir(0,)C1(CO)[P(C,H,)3],, in which the Ir has a trigonalbipyramidal structure.Group WII.-Nickel, palludium, platinum. In bis-(2,2,6,6-tetramethyl-heptane-3,5-dionato)nickel(n), the nickel atom has a planar stereochemistrywith a mean nickel-oxygen distance of 1.836 A, considerably shorter thanthe corresponding octahedral values. This is possibly due to the absenceof electrons in the anti-bonding o-molecular 0rbita1.l~~ A two-dimensionalneutron diffraction analysis of the crystal structure of tetragonal nickelsulphate hexadeuterlate lP7 shows that all the deuterium atoms participatein non-linear hydrogen bonds; Ni-0 bond lengths range from 2.02-2-10 8.The nickel(@ ion is octahedrally surrounded by oxygen atoms in crystals oftrisilver dinitrate tris(acetylacetonato)nickelate(n) monohydrate.148 MeanNi-0 distance is 2-04 A. Silver ions are bonded to the central carbon atomof one chelate ring and to the oxygen atom of an adjacent ring; mean dis-tances are Ag-c, 2.34 and Ag-0 2.468.The crystal structure of bis-(triphenylmethylarsonium)tetrachloronickel(n) has been determined andshown to be isomorphous with the chlorides and bromides of Mn, Fe, Co,and Zn.The compound is formulated as [Ph3MeAs],[NiC1a and containstetrahedral(NiC14)2- ions.149 Three chlorine atoms of each complex ion arecrystallographically equivalent but the tetrahedron is regular, within experi-mental error: Ni-C1, 2.27 8; C1-Ni-C1, 109" 19' and 109" 38'. There is aconsiderable degree of accidental symmetry in the crystal; thus, there aretwo crystallographically distinct kinds of [Ph3MeAs] + ions, but arsenic,nickel, one chlorine and three methyl-carbon atoms lie in special positions.The copper chloride and bromide complexes are isomorphous with each otherbut not with the others. Crystals of the tetraiodides of IMn, Fe, Co, Ni, andZn are isomorphous but with a different crystal structure from the chloridesand bromides.Two five-co-ordinate nickel(=) complex structural analyses have ap-peared.With the ligand N-~-diethylaminoethyl-5-chlorosalicylaldimine,six-co-ordination is effectively prevented by steric hindrance of two ethylgroups.150 The five-co-ordination polyhedron may be described as a distortedsquare pyramid formed by two oxygen atoms, the two azomethine nitrogenatoms, and the #I-nitrogen atoms of one ethylenediamine group. This is theS. L. La Place and J. A. Ibers, Inorg. Chem., 1966, 5, 406.14* F. A. Cotton and J. J. Wise, Imrg. Chem., 1966, 5, 1200.147 B. H. O'Connor and D. H. Dale, Acta Cryat., 1966, 21, 705.14* W. H. Watson, jun., C.-T. Lin, Inorg. Chem., 1966, 6, 1074.lSd P. L. Orioli, M. Di Vaira, and L. Sacconi, J . Amer. Chem. SOC., 1966, 88,4383.P.Pauling, Inorg. Chem., 1966, 5, 1498GERLOCH AND MASON 713first complete structure of a high-spin five-co-ordinate nickel II) ~omp1ex.l~~The geometry of the ligand also determines the distribution of the donoratoms about the atom in another high-spin nickel@) complex. In bis(sa1icyli-dene-y-iminopropyl)methylaminenickel(n) the metal atom has a distortedtrigonal bipyramidal co-ordination geometry, being co-ordinated by twooxygens and three nitrogens.The complex tetramethylenedinitramine(diaquo)nickel( n) forms poly-meric chains in which each ligand molecule spans two nickel atoms, bothnitramine groups being co-ordinated.152 The nickel co-ordination-octahedronis made up of two HzO molecules (Ni-0 is 1.99 8) and the nitramine groupsof two different molecules.The nitramine group acts as a chelate ligand;one oxygen atom (Ni-0 is 2.16 8) and one amino-nitrogen (Ni-N is 2.23 8)are co-ordinatled so that the nickel atom is then part of a four memberedring. There is a significant distortion from square planar co-ordination ofthe metal in a macrocyclic tetraiminenickel(n) complex.153 The tetenepossesses the cis arrangement of the gem-dimethyl and imine groups. Fourimine groups in the molecule are evidenced by short C-N bonds. The ethyl-enediamine residues are in the gauche configuration. Ni-N distances are1-82 and 1-97 8.Bis- (N-methylsalicyla1diminato)-nickel@) and bis(N-isobutylsalicylaldi-minato)nickel(rr) have square planar configurations as also evidenced bytheir diamagnetism, whereas bis- (N-isopropylsalicylaldiminato)nickel(n)contains the tetrahedrally co-ordinated meta1.154 Ni-0 and Ni-N distancesare 0.07 A longer in the tetrahedral molecule than in the planar ones.Themetal is out of the planes of the ligand residues in the N-isopropyl andN-isobutyl complexes but not in the N-methyl compound where symmetryconsiderations prevent this. By contrast, the nickel atoms in bis-(N(iso-propyl- 3 -met h ylsalic ylaldim inat 0) nickel ( II) have a planar rat her than tetra-hedral ~tereochemistry.l5~ Considerations of steric factors explain the causeof the tetrahedral configuration of N-sec.-alkyl-substituted salicylaldiminechelates, but give no clue as to the reason for the planar configiiration of the3-methyl chelate.Bis-(N-phenylsalicyla1dimiiiato)nickel (and the isomor-phous copper complex) is planar 156 with Ni-0 distances of 1.825, Ni-N1-908 A. The metal atom is 0.475 8 out of the plane of the chelate groupto give a " stepped " arrangement.The majority of structures of nickel complexes have involved nickel-sulphur bonds. In the complex [NiC,H,ON,S,], the two S,Nz groups are incis positions unlike the situation in the dimethyl derivstive.157 Nickel issquare planar with Ni-N 1.90 and 1-97 8; Ni-S 2.15 and 2-16 A; N S dis-tances range from 1.51-1-698. There is a slight tetrahedral distortionfrom square planar in the co-ordination of nickel in diacetylkis(mercapto-ethylimine)nickel(11).~~8 Mean Ni-S bond length is 2.16 and Ni-N 1-86 A.lS1 P. L.Orioli, M. Di Vaira, and L. Sacconi, Chem. Comm., 1966, 300.lS8 P. 3f. Liebig, J. H. Robertson, and M. R. Truter, J . Chem. SOC. ( A ) , 1966, 879.lSs I. E. Maxwell and M. F. Bailey, Chem. Comm., 1966, 883.164 M. R. Fox, Dks. Abs., 1966, 27, B, 127.lK6 R. L. Braun and E. C. Lingafelter, Acta Cryst., 1966, 21, 546.166 R. V. Chastain, jun., Dks. Abs., 1966, 27, B, 124.Is' J. Weisa and U. Thewalt, 2. anorg. Chem., 1966, 343, 274.l6* Q. Fernando and P. J. Wheatley, Inorg. Chem., 1965, 4, 1726714 CBYSTALLOQRAPHYThe nickel(=) ion, in bisthioureanickel(n) thiocyanate, is octahedrally co-ordinated by four thiourea sulphur atoms (Ni-S distances are 2-63 and2*56& and two thiocyanate nitrogens (Ni-N is 1-99&.lba This is verysimilar to the arrangement in thiosulphatotetrathioureanickel(rr),16~ whereagain four thiourea molecules co-ordinate to the nickel by sulphur atomswith thiosulphate co-ordination by one sulphur and one oxygen atom.TheNi-S (thiosulphate) distance is longer than the Ni-S (thiourea). In bis(cis-1,2-diphenylethene-l,2-dithiolato)nickel, the environment of the nickel is strictlyplanar; 161 Ni-S is 2-10 8. A comparison of bond lengths from relatedstructures shows that the variation in the formal charge on the complexdoes not correspond to changes of oxidation state of the metal but ratherresults in extensive ground state Belocalization. In bisdithiocarbamate-nickel(n),ls2 the co-ordination of the nickel is a slightly distorted squareplane, the average Ni-S bond length being 2-21 8.A mixed sulphur- andoxygen-donor complex of nickel is shown in the structure of a complex withmethylthiohydroxamic acid.163 The nickel is square planar as is also thefive-membered chelate ring. (Ni-0, 1-87 ; Ni-S, 2-16 8.)An interesting nickel-sulphur complex is represented by the analysis lt14of mi(Sc2H5)&. Six nickel atoms in a ring are each bridged to neighboursby two SC2H, groups, which are all bridging symmetrically, the alkyl groupsbeing alternately axial and equatorial. A very similar structure is that ofnickel 2-hydroxethylmercaptide 165 in which planar hexagons of sulphursandwich a staggered planar hexagon of nickel atoms (14). The correspond-ing palladium complex is isomorphous. In accord with the dimagnetism of16# M.Nardelli, G. F. Gasparri, G. G. Battistini, and P. Domiano, Acta Cryst., 1966,160 0 . F. Gasparri, A. Musatti, and M. Nardelli, Chenz. Comm., 1966, 602.16p L. Capacchi, M. Nardelli, and A. Villa, Chem. Comm., 1966, 441.L63 T. Sato, K. Nagata, M. Shiro, and H. Koyama, Chem. Comm., 1966, 192.16s R. 0. Gould and R. M. Taylor, Chem. and Ind., 1966, 378.20, 349.D. Sartain and M. R. Truter, Chem. Comm., 1966, 382.P. Woodward, L. F. Dahl, E. TV. Abel, and B. C. Cross, J . Amer. Chern. SOC.,W65, 87, 5251GERLOGH AND MASON 715these complexes, the nickel is approximately square planar. Again, intriphenylmethylphosphoniumbis( 1,2-&cyanoethylene- 1,2-&thiolato)nickel-ate(m), the nickel is square planar, with an average Ni-S distance of2-15 k 1 S S The magnetism of this complex is explained in terms of super-exchange between nickel atoms via sulphur.The crystal structure of K,[Pd(C,O,),] ,4H,O involves square planarpalladium with oxygen atoms of other complex planes acting as nearestout-of-plane neighbours to the metal.167 Pd-0 bond lengths are 1-98 and2-02 A.Two interesting and related palladium complexes are representedin the molecular structures of &-hydroxyquinolinatopalladium(~~) 168 andthe 1 : 1 complex of bis-8-hydroxyquinolinatopalladium(n) and 1,2,4,5-tetra~yanobenzene.1~~ In the former compound, the structure consists ofplane- to-plane stacks of planar centrosymmetric hydroxyquinolinatopal-ladium(n) molecules. The palladium co-ordination is really square planar butaromatic carbon atoms 3-36 A away inneighbouring molecules complete a verydistorted octahedron.In the complex with 1,2,4,5-tetracyanobenzene, therelative orientation of the donor and acceptor molecules is intermediatebetween that of the corresponding 1 : 1 chloranil complex and of the 2 : 1bis-8-hydroxyquinolinatocopper (n) picryl azide complex. Palladium-sulphurco-ordination 17* in Pd(NS,), leaves palladium with a square planar stereo-chemistry, Pd-S distances being 2*25-2*29 A.The major interest in the structure of the pentafluoroxenonylhemfluoro-platinate(v) (15) is the essentially square pyramidal arrangement of fivefluorines in the [XeF,]+ ~ati0n.l’~ The average Xe-F distance is 1.908,with the axial value Xe-F of 1-77 A. The [PtF6]- ion in this structure isapproximately octahedral, with an average Pt-3’ distance of 1-91 A.Aneutron diffraction analysis 172 of O,PtF, affords rather more accurate dataon the geometry of the PtF6 ion, which in this case is shown to be a regularC. J. Fritchie, jun., Acta Cryst., 1966, 20, 107.lS7 I(. ICrogmann, 2. a w g . Chern., 1966, 346, 188.188 C. K. Prout and A. G. Wheeler, J. Chem. Soc. (A), 1966, 1286.169 B. Kamenar, C. K. Prout, and J. D. Wright, J . Chem. Soc. (A), 1966, 661.170 J. Weiss and H.-S. Neubert, 2. Naturjorsch., 1966, 21b, 286.171 N. Bartlett, F. Einstein, D. F. Stewart, and J. Trotter, Chern. Comm., 1966, 550.17a J. A. Ibera and W. C. Hamilton, J. Chern. Phys., 1966, 44, 1748716 CRYSTALLOGRAPHYoctahedron with Pt-3’ bond lengths of 1-82 & 0.03 8.Unfortunately, theoxygen-oxygen bond length could not be determined with high precisionowing to the probability of dynamic or static disorder of the oxygen groups.Data are compatible with the probable formulation of the complex asO,+,PtF,-, although other formulations cannot be eliminated.Low-temperature (120 OK) crystal structure analyses of c k and trans-dichlorodiammineplatinum (11) have been reported.17 The trans-isomerstructure a t low temperature is essentially the same as the room-temperaturestructure of Porai-Koshits. In the cis-complex, the planes stack up in sucha way as to give Pt-Pt bond lengths which alternate between 3.372-3409 A,perhaps short enough to involve some interaction; in the tram-compoundthe Pt-Pt vector is 5-0 A.Platinum-chlorine and platinum-nitrogen bondlengths in the cis- and trans-complexes are, respectively, Pt-C1, 2.33 and2.32, and Pt-N 2-01 and 2.05 8. The co-ordination of the platinum ions intetraethylamineplatinum(n) dibromotetraethylamineplatinum(m) tetra-bromide is quite conventional;174 Pt-N bond lengths are 2.06 A. The firststructure determination of a zerovalent platinum complex is that of tristri-phenylphosphineplatinum(0) 175 in which the platinum is essentially trigonalplanar, with mean Pt-P distance of 2-26 8. The structure of a platinum (rv)complex 176 containing a metal-carbon o-bond which was formed by theP1’3 G. H. W. MilburnandM. R. Truter,J. Chem. Soc. (A), 1966, 1609.174 B. M. Craven and D. Hall, Acta Cryst., 1966, 21, 177.175 V.Albano, P. L. Bellon, and V. S . Scatturin, Chem. C m . , 1966, 607.17s M. A. Bennett, 0. J. Erskine, J. Lewis, R. Mason, R. S. Nyholm, G. B. Robertson,end A. D. C . Towl, Chem. Comm., 1966, 395GERLOCH AND MASON 717re-arrangement of bromination of a square planar platinum(@ complexshows that the trans effect of a a-bonded carbon atom on the platinum halogenbond lengths amounts to 0.1 A.Organometccllic compounds. The stereochemistry of PP'P"P'''-tetrakistri-carbonylnickel tetraphosphorus, P4O6[Ni(CO)& has been determined frompowder photography 177 and is shown in (16). In the structure of cyclo-octenylnickel(n) acetylacetonate, the acetylacetone ligand co-ordinates as ausual bidentate group, which is symmetrical.178 Three atoms of the eight-membered cyclo-octenyl ring lie at approximately 2 A from the nickel atom,the next closest approach being 24B.The bonding of the ring to thenickel is thus similar to that found in PtC1( OMe)(dicyclopentadiene),In contrast to the situation in n-allylpalladium chloride, the methallylgroup in triphenylphosphinemethallylpalla&um chloride is asymmetricallybonded to the palladium as evidenced by significant differences in the metal-carbon bond lengths.179 The methallyl group itself is non-planar. Anotherpalladium complex involving n-bonding to an allyl group is acetylacetonato-cyclo- o c ta - 2,4-dienylpalladium. The three at oms constituting the n- allylgroup are a t an average distance of 2-11 A from the metal, whereas theremaining two atoms of the conjugated system are 2.91 and 3-03 A distantfrom the metal.lgOSeveral organometallic derivatives of platinum are of interest.In tri-methyl-(8-quinolinato)platinum(Iv), the bond lengths are : Pt-C(methyl),2.068; Pt-0, 2.24, and Pt-N, 2,138. The Pt-Pt distance of 3.388 is1 7 7 E. D. Pierron, P. J. Wheatley ,and J. G. Riess, Acta Cryat., 1966, 21, 288.l78 0. S. Mills and E. P. Paulus, Chem. Cmm., 1966, 738.17* R. Mason and D. R. Russell, Chem. Comm., 1966, 26.l8@ M. R. Churchill, Inorg. Chem., 1966,5, 1608718 URYSTAILLOQRAPHYprobably too large for simple metal-metal bonding. Each platinum is octa-hedral, sharing two oxygens with symmetrical bridges.lsl In PtCl(0Me)-(dicyclopentadiene),182 the metal is essentially square planar, and it is ofinterest that, as noted previously, the platinum-halogen bond trans to the0-bonded carbon atom is 0-17 8 greater than that tram to the n-bond.Thestructure analysis excludes a formulation of the structure involving ally1bonding to the metal. The structures of cyclopropane adducts of platinumhave been determined.lsS In bispyridine-tram-dichloroplatinum(a) cyclo-propane, the cyclopropane acts as a simple chelating ligand. This complexundergoes rearrangement in which the C, fragment adds to a pyridiniumion to give a platinum(1v) complex of an ylide (17).Group n.-complex fluorides of the types, Cum6,4&0 (M = Si,Ti,Zr, Sn, or W), CuMOF,, 4H,O (M = Nb) and CuM0,F4,4H,0 (If = W)have been shown to be isotypes, all involving six-co-ordinate copper atomsin D4,, symmetry.lS4 The complexes, NH4cum,,4w,o (M = Si, Ti, Sn)and hW4CuM0,F,,4Hz0 (M = W), also isotypic, are double salts and may beformulated as Cu(H,O),ME’,,~,F and Cu(H,O),,M0,F4,NH4F.An accurate re-determination of the crystal structure of CsCuC1, showsthat there is a Cu-Cu separation of only 3.062 A but overlap integral calcula-tions exclude the possibility of direct Cu-Cu bonding.ls5 The close approachof the copper atoms results from sharing faces of octahedra rather thanedges, as is often found in related structures.This interpretation differsfrom that originally put forward. Essentially isolated cu2c162- dimers occurin the crystal structure of (CH,),NH,CuCl,, although infinite chains resultfrom the formation of long Cu-C1 bonds, a t 2.733 Within the dimersthe bridged Cu-C1 bonds are 2-32, non-bridged approximately 2.27 8.Thestructure has effectively five-co-ordinate CU(II) ions. The dimer has Cisymmetry although there are significant deviations from ideal D,,, symmetryin the clu,C1,z- ion. In the crystal structure (18) of [CO(NH,)~]~CU,C~~,,hexaminecobalt(m) ions, CU,CI~,~~- ions and three chloride ions are packedtogether in the ratio 4 : 1 : 1. The hexaminecobalt(rn) ions have normalcobalt-nitrogen bond lengths of 1-99 8 and form a sodium chloride latticewith terminal copper atoms, the Cu-Co distance being 5-45 A. The pointgroup symmetry of the Cu,Cll,ll- ion is Td, bridging chlorines linkingtogether a central tetrahedron with four outside tetrahedral CuCld2- ions.Chlorine bridges are asymmetric, Cu-C1 distances being 2.48 and 2*26Arespectively.187Crystal structures have been reported for three tetra-amminecopper(r)dihalogenocuprates(I).188 In Cu(NH3)4(&12),, Cu(NH,),(CuBr,),, andCu(NH,),(CuCl,),,H,O, the cupric atoms are in square planar co-ordination1 8 1 J.E. Lydon and M. R. Truter, J . Chem. SOC., 1965, 6899.182 W. A. Whitla, H. M. Powell, and L. M. Venanzi, Chem. Comm., 1966,310.18s N. A. Bailey, R. D. Gillard, M. ICeeton, R. Mason, and D. R. Russell, Chem.Comm., 1966, 396.184 J. Fischer, A. De Cian, and R. Weiss, Bull. SOC. chim. Prance, 1966, 2646;A. De Cian, J. Fischer and R. Weiss, ibid., p. 2647.185 A. W. Schleuter, R. A. Jacobson, and R.E. Rundle, Inorg. Chem., 1966,5,277.186 R D. Willett, J . Chem. Phys., 1966, 44, 39.187 P. Murray-Rust, P. Day, and C. K. Prout, Chem. Cormn., 1966, 277.188 J. A. Baglio, Diss. Abs., 1966, 27, B, 123GERLOCH AND MASON 719sites, bonded to four nitrogens with mean clu-N distances for iodide, bromideand chloride complexes, of 2-14,2.00 and 2-03 A, respectively. The cuprousatoms are tetrahedrally co-ordinated to four halide atoms, and the tetra-hedra share edges to form infinite chains. The orientation of the Cu(Nf3[,),planes with respect to the tetrahedra is different in the iodide as comparedwith the chloride and bromide, with the result that there are Cu-I inter-actions of 3-17 A tending to complete octahedral co-ordination. It is sug-gested that the electronic spectrum of the iodide is of the charge-transfer typewhile that in the other halide is dd; the iodide is dark-green and the chlorideand bromide appear violet.The chloride has the same structure as thebromide, except for the location of bridging R,O molecules perpendicularto the cupric ammine planes.In another analysis of Tutton's salts, the copper ion in copper ammoniumsulphate hexahydrate is surrounded by chains of water m0lecules.1~~ Theoctahedron around the copper shows a rhombic distortion with three metal-oxygen bond distances ranging from 1-96 to 2.22B. A detailed neutrondiffraction analysis has been made of the structure of copper formate tetra-hydrate together with a study of the antiferroelectric phase transition.lg@Hydrogen atomic co-ordinates have been determined. Data on the anti-ferroelectric phase transition has been collected a t -38-9 '.The orientationof the water molecules is disordered to allow all possible short 0-0 contactsto be hydrogen-bonded. The phase transition is probably caused by hydro-gen motions, similar to those in ice. There is no discontinuity in the co-efficient of expansion of crystals a t the transition temperature. Anextremely interesting co-ordination of copper is represented in the structurel*@ R. Montgomery and E. C. Lingafelter, Acta Cryst., 1966, 20, 659.lg0 K. Okada, M. I. Kay, D. T. Cromer, and I. Ahodovar, J. Chm. Phys., 1966,44,1648720 CRYSTALLOGRAPHYof copper@) nitratenitromethane. The copper has effectively a tetragonalpyramidal co-ordination with four basal nitrate groups and one axial nitro-methane.The square bases are linked diagonally by bridging nitro-groupsto form sheets; the Cu-0 basal value is 1.958; Cu-0 (nitromethane) is2-31 A.lQlA new formulation of the overall structure of bis(ethy1acetonacetato)-copper(@ has been given.lg2 The copper ions in cupric tropolone are notstrictly planar. lQ3 The tropolone ligand itself shows bond alternation andthe interpretation of the distortion from strict planarity of the ligsnd fieldaround the copper ions (which is similar to the " step " arrangement dis-cussed by Holm) is that it leads to more efficient packing of the molecules inthe crystal. The molecules are arranged in infinite stacks. The crystalstructures of two copper(n)a-hydroxy- and a-alkoxy-carboxylates have beendeterrnined.lQ4 In bisglycollatocopper(n) there are four short copper-oxygencontacts of 1-93 A in the chelate ring and two long contacts of 2-64 A, tocarboxyl oxygens of neighbouring molecules.In bismethoxyacetato-copper(@, two short contacts of 1.93 A to carboxyl groups, two long con-tacts of 2*14A to the methoxy-groups in the chelate ring, and two watermolecules a t approximately 2.14 A complete a six-fold co-ordination. In-finite chains of covalently bonded binuclear units occur in the crystalstructure of copper(=) succinate dihydrate.lQ5 Each of the binuclear unitsclosely resembles that found in copper(n) acetate. In the succinate, theCu-Cu separation is 2.61 A and is consistent with the fact that there ismagnetic exchange in this molecule.The structure of one of several differentcrystalline forms of triaquo-2,6-pyridinedicarboxylatocopper has been deter-mined,lQs A hydrogen-bonded network in the crystal involves each oxygenatom, although both trigonally and tetrahedrally arranged bonds to theoxygens are involved. Co-ordination about the copper atom in copperglutamate dihydrate lg6 is approximately square planar, involving twooxygen atoms, a glutamate nitrogen atom, and a water molecule. Cu-0 andCu-N distances range from 1*97--2.00 8. Two additional glutamate oxygenatoms at 2.30 and 2-59 A complete a, severely distorted octahedron. Eveof the available protons are involved in hydrogen bonding.I n a copper(1) cyanide-hydrazine c0mplex,1~~ the copper has a distortedtetrahedral ligand field.The copper cyanide forms zigzag infinite chains,these being joined by hydrazine molecules to form infinite puckered layers.Octahedra share corners to link into chains in CU(N,),(NH,),.~~~ Nitrogen-nitrogen distances in the azide are 1.174, 1.142, 1.19 and 1.14g.In the y-form of bis-(N-methylsalicylaldiminato)copper(~~),~~~ each metalatom is five-co-ordinate in a distorted square pyramidal configuration.181 B. Duflfin and S. C. WalIwork, Acta Cry&, 1966, 20, 210.102 D. Hall, A. J. McKinnon, and T. N. Waters, J . Chem. SOC. (A), 1966, 616.I** W. M. Macintyre, J. M. Robertson, and R. F. Zahrobsky, Proc. Roy. 80% 1966,104 J. C. Forrest, C. K.Prout, and F. J. C. Rossotti, Chern. Cormn., 1966, 658.1'6 B. H. O'Connor and E. N. Mwlen, Acta Cryst., 1966,20, 824.106 C. M. Gramacciolo and R. E. Marsh, Acta Cryst., 1966, 21, 594.107 D. T. Cromer, A. C. Larson, and R. B. Roof, jun., AC~U Cryst., 1966,20, 279.108 I. Agrell, Acta Chem. S c a d . , 1966, 20, 1281.199 D. Hall, S. V. Sheat, and T. N. Waters, Chem. C m . , 1966,436.A, 289, 161GERLOCH AND MASON 721Cu-0 and Cu-N bond lengths in the " monomer " are bridged by two Cu-0bonds of mean length 2.44 8. The structure is reported of a copper S c Mbase complex formed from two moles of pyridine aldehyde and one mole ofethylenediamine with Cu(@ ions.200 The crystals consist of perchlorateanions and complex copper cations. The metal is five-co-ordinate from thequadridentate nitrogen ligand and one bromine atom.Two Cu-N distancesare about 2-02 and the others are 2.94 and 2.12 A; Cu-Br is 2.40 8. Thestereochemistry is described as neither square pyramidal nor trigonal bi-pyramidal but intermediate between the two, although there is a remarkablesimilarity to the geometry of Co(paphy)Cl, and Zn(terpyridine)Cl, (q.~.).Tetragonal pyramidal co-ordination of the copper ion occurs in di-p-hydroxobis( dimethylaminecopper(n) ) sulphate monohydrate in which thetwo crystallographica.11y independent metal atoms are each co-ordinated bytwo hydroxyl anions and two nitrogen atoms of methylamine to form abinuclear complex ion.201 Two hydroxyl ions are shared by two copperatoms. The complex ion is puckered a t the hydroxyl ion, resulting in theclose approach of 2.78 A between the copper atoms.In effect, this is a dimerin which the hydroxyl ion in one of the complex ions is co-ordinated as a fifthligand to the copper ion in the other. The molecules of bis-( l-phenylbutane-1,3-dionato)copper(n) are monomeric, the four oxygens in the copper ionare exactly coplanar with Cu-0 distances 1-94 and 1.91 A . Z O z Square planarco-ordination of the copper atom is also recorded in bis-( 1,3-diphenylpropane-1,3-dionato)copper(11) ; the mean Cu-0 bond length is 1.91 A.203 The chelatering is entirely planar, the phenyl rings making only very small angles withthis plane. The bond lengths show that there is no extensive conjugationbetween the phenyl rings and the chelate ring system. In bisbiuretcopper(rr)dichloride, the molecule has exact Ci symmetry.204 The biuret molecules arebidentate chelates, octahedrally co-ordinated and, again, there is a step-likestructure, as discussed previously.Several papers have been written on the relation of colour isomerism tostructure in copper co-ordination compounds.The crystal structure ofNN'-ethylenebis (acetylacetoneiminato) copper (n) monohydrate, bis-salicyl-aldiIninatocopper(n) and bis-(N-t-butylsalicylaldiminato)copper(rr) recordfive-, four-, and four-co-ordinate copper respectively.205 In the first com-plex, a water molecule occupies the axial site of a square pyramid; in thesecond [which is isostructural with bis-salicylaldatonickel(lr)] , the ligandsare planar, but not coplanar, giving rise to the usual stepped arrangementwhich, is here ascribed to the effects of crystal packing.There are numerousCu-nearest ligand contacts of about 3-1-3.28. Mean Cu-0 and Cu-Ndistances are 1.91 and 1.90 8. In the third compound the geometry aboutthe copper is that of a flattened tetrahedron, with mean Cu-0 and Cu-NB. F. Hoskins and F. D. Williams, C h m . Comrn., 1966, 798.Y. Iitaka, K. Shimizu, and T. Kwan, Acta Cryst., 1966, 20, 803.*Is Ping-Kay Hon, C. E. Pfluger, and R. L. Belford, Inorg. Chem., 1966, 5, 616.M. Blackstone, J. van Thuijl, and C. Romers, Rec. Trav. chim., 1966, 85, 657.H. C. Freeman and J. E. W. L. Smith, Acta Cryst., 1966, 20, 153.IoC D. Hall, H. J. Morgan, and T. N. Waters, J .Chern. SOC. (A), 1966, 677; E. hT.Baker, D. Hall, and T. N. Waters, ibid., p. 680; T. P. Cheeseman, D. Hall, and T. N.Waters, ibid., p. 685722 CRYSTALLOQBAPHYdistances of 1-90 and 1.98 8. There is also flattened tetrahedral co-ordina-tion of the copper atom in NN'-(2,2'-biphenyl)bis(salicylaldiminato)-Bond lengths are: Cu-0, 1.90 A and Cu-N, 1.94 and 1.96 8.Copper is square planar in bis(N-2-hydroxyethylsalicylaldiminato)copper-(II). 207 Complex molecules, methyl ammonium ions, and perchlorate ionsall exist independently in a lattice complex of NN'-ethylenebisacefylace-toneiminatocopper (II) .20*In glycyl-L-histidinecopper(n), the copper is square pyramidal with along Cu-0 (water) bond of 2.47 In ethylenebisguanidinecopper(n)chloride monohydrate the three-ring tetrachelate ligand is planar with aCu ion in the plane; 210 Cu-Cu distances range from 347-3069 8.It is ofparticular interest that the ethylenebisguanidine ligand is a very strong onewhich will, for example, stabilise the silver(m) oxidation state. The copperion in bis- (N-isopropylsalicylaldiminato)copper(n) has a flattened tetrahedralstereochemistry and is isomorphous with the nickel analogue ; 211 the tetra-hedral angles are 95" (2), 100" (2), and 137 " (2) and mean Cu-0 distances are1-875 and Cu-N 10985A.Two structural analyses of L-alanine copper complexes have been com-pleted and together they offer the first example of cis-trans-isomerism incopper complexes. In trans-bis-I;-alinatocopper(rr), the copper ion is in adistorted octahedron with two very long Cu-0 bonds.212 In the case of thecis-complex structure, the stereochemistry of the copper ion is essentiallyone of a distorted square pyramid with carbosyl oxygen atoms bridgingcopper ions in a polymeric structure.The sixth position of the octahedronis filled by a methyl group of a neighbouring mole~ule.2~~Several structures have been reported for complexes with a sulphurligand. Complex CuIT(NH3),2+ cations and Na+ ions occur with the catena-anions, Cu ( s@,) 2n 3 -, in t e tr asodiumt e t ra- amminecopper ( II) di - catena - di-p-thiosulphstocuprate(~) ,214 Co-ordination around the cupric ions is purelysquare planar with no atom completing a distorted octahedron or any five-co-ordinate geometry.The anion is formed by cuprous ions, tetrahedrallyco-ordinated by four thiosulphato-groups, one sulphur bridging two copperions to give a chain structure. A second analysis of the crystal structure ofcopper@) diethyldithiocrtrbamate has been r e p ~ r t e d . ~ l ~ In copper diethyl-thiocarbamate, the metal ion has a square pyramidal geometry; four sulphuratoms in the plane lie a t distances ranging from 2*30--2*34A, the apicalsulphur being positioned a t 2.85 A from the sulphur.210 The ligands are206 T. P. Cheeseman, D. Hall, and T. N. Waters, J . Chem. SOC. ( A ) , 1966, 1396.209 E. R. Boyko, D. Hall, M. E. Kinloch, and T. E. Waters, Actu Cryst., 1966,21,614.208 N. F. Curtis, E. N. Barker, D. Hall, and T. N. Wators, Chem. Comm., 1966, 675.209 J.F. Blount;, K. A. Frazer, H. C. Freeman, J. T. Szymanski, C.-H. JVang, and210 N. R. Kuncher and M. Mathew, Chem. Comm., 1966, 86.z12 A. Dijkstra, Actu Cryst., 1966, 30, 585.213 R. D. Gillard, R. Mason, N. C. Pame, and G. B. Robertson, Chem. Cmrn., 1966,214 A. Ferrari, A. Braibanti, and A. Tiripicchio, Acta Cryst., 1966, 21, 605.*16 B. H. O'Connor and E. N. Maslen, Actu Crpst., 1966, 21, 828.216 M. Bonamico, C.. Dessy, A. Mugnoli, A. Vaciago, and L. Zambonelli, Acto Crytit.,F. R. N. Gurd, Chem. Comm., 1906,23.P. L. Orioli and L. Sacconi, J . Anzer. Chem. SOC., 1966, 88, 277.155.1965,19, 886QERLOCH AND MASON 723planar. It is of particular interest that the analogous zinc complex 217 isbased on a trigonal bipyramidal co-ordination of the zinc, although the twocompounds are virtually isomorphous.In the zinc compound the thio-carbamate ligands act in two distinct ways : as a bidentate group to one zincand as a bridge between two zinc atoms. In the molecule 2-keto-3-ethoxy-butyraldehyde bis( thiosemicarbazone) 218 the chain from the two extremesulphurs is fully extended and the nitrogen-nitrogen conjugated systems areapproximately planar. Co-ordination to the cupric ion is via two nitrogenand two sulphur atoms so that the ligand is tetradentate. The copper ionsare approximately octahedral with two very long axial Cu-S bonds.In the crystal structure of CU~[SC(NH,)~]~(NO,),, a rectangle of copperatoms is connected by bridging sulphur atoms of thiourea groups.219 Therectangles are in turn connected by other sulphur bridges to form an infinitepolymer of sulphur-bridged copper atoms propagating in the crystal c direc-tion.The &(I) atoms are tetrahedrally co-ordinated and there exist no lessthan five distinct types of metal-sulphur bonds. The nitrate groups merelyfdl holes in the lattice.An essentially ionic structure 220 exists in succinonitrilosilver nitrate,BAgNO,,NC(CH,),CN, involving complex silver cations and nitrate anions ;Ag-N distance is 1.97A. The succinonitrile group is found to take thetram configuration. In the structure of a 1 : 1 silver nitrate-pyrazinecomplex,221 there are almost planar " W e d " chains of [-Ag-NC4H4N-J,with Ag-N distances of 2-21 A and N-Ag-N angles of 160". The next-nearest neighbours of the Ag(1) ion are two oxygens of a nitrate group at2.72 and two other nitrate oxygens a t 2.948.An X-ray investigation ofsilver nitrate 228 shows the crystal structure to be unique, a t least in com-parison with other metal nitrate structures. No oxygen atom is uniquelyassociated with any one silver ion and the resulting three-dimensional ionicstructure is attributed to the high polarising power of the small silver ions.In AgC(CN),, each silver ion co-ordinates to three nitrogen atoms, one at2.21 and two at 2-25 A.223 The probable symmetry of the C(CN),- groupis D3h.Of interest is the crystal structure analysis of bis(thiourea)silver(I) chlor-ide 224 which contains distorted tetrahedra of three sulphur and one chlorineatoms, sharing two apical sulphur atoms with neighbours to form infinitmespiralling chains.The repeat-unit involves the chain, -Ag-S-Ag-S-Ag-, inwhich the two sulphur bridges are quite different. One subtends an angleof 77", the other 133", giving rise to one long and one short Ag-Ag contact(4.71 and 3-13 A, respectively). A molecular orbital model is discussed forthe possible interaction between two silver atoms. The Ag-S bond lengthsM. Bonamico, G. Mazzone, A. Vaciago, and L. Zambonelli, Acta Cryst., 1965,19, 898.*la M. R. Taylor, E. J. Gabe, J. P. Glusker, J. A. Minkin, and A. L. Patterson, J .Amer. Chem. SOC., 1966,88, 1845.21* R. 0. Vranka and E. L. Amma, J . Amer. Chenz. Soc., 1966, 88,4270.t 2 0 T. Nomura and Y. Saito, Bull. Chem. SOC.Japan, 1966, 39, 1468.221 R. G. Vranka and E. L. Amma, Inorg. Chem., 1966, 5, 1020.P. F. Lindley and P. Woodward, J . Chem. SOC. (A), 1966, 123.J. Konnert, and D. Britton, Inorg. Chem., 1966, 5, 1193.E. A. Vizzini and E. L. Amma, J . Amer. Chem. SOC., 1966, 88, 2872724 CRYSTALLOGRAPHYin the bridges range from 2*48-2*54& while the non-bridged Ag-S bondlength is 2-438; the Ag-Cl bond completing the distorted tetrahedra is3.04 8.Orgunometullic compounds. In the structure of C,H,CUYA.lC14, the &(I)ion is in a distorted tetrahedral environment with three metal-chlorinebonds and one n-type metal ion-aromatic interaction.225 The three Cu-Clbonds (2.37, 2-40 and 2-56A) interact with different AlC1,- tetrahedra insuch a way that a pleated sheet of Chdc1,- is formed, with ch-C,H, linkagesprotruding from the sheet.Of importance is the copper(1) ion locatedalmost directly above the G-C bond of a benzene ring, with Cu-C distancesof 2-15 and 2-30If. The anions clearly play an important part in thestability of this complex.Five-co-ordinate sfiver(1) ions exist in c,H,,AgAlCl4. Four Ag-Cl dis-tances range from 2.59-3-04 A and one silver-benzene interaction withan Ag-centre of a G C bond, is 2.57 8. The structure is made up of infiniteplanar sheets, again composed of AlC1, tetrahedra connected by Ag-C1 bonds,and n-type Ag-aromatic interactions perpendicular to the sheet.226 Thestructure of silver bullvalene (bullvalene is tricycle[ 3,3,2,0]deca-2,7,9-triene)involves the metal bonded to three bullvalene The bonding toeach ligand is to two olefin bonds, but their approach to the metal is notequal; there are two short (2.4 8) and two long (3.5 8) contacts allowinga possible twelve Agf-C interactions in the complex.In a nonbornadienesilver nitrate complex,228 silver atoms are connected in chains by**O-N-O** links of the nitrate groups. One double bond of the olefinforms the third ligand about the silver ion. The axis of the double bondlies approximately in the plane of the O***Ag*-O link of the chain sothat the co-ordination about the silver is triangular planar. Both doublebonds of the olefin are co-ordinated to the silver atoms so that the olefinforms a cross link between two silver-NO, chains. In phenylethynyl(tri-methylphosphine)silver(1),2~~ the structure in the crystal is one of an infinitepolymer, the silver ions having a distorted tetrahedral co-ordination bybonding to two phosphorus atoms and to two acetylinic links in adjacentchains.Group IIb.-Zinc is tetrahedrally co-ordinated by three bromines andone water molecule in t~-KZnBr,,2H~O.230 Potassium ions are surroundedby seven bromines and two waters.A neutron diffraction analysis ofpotassium zinc cyanide shows that a freely rotating cyanide group may beruled out, and the best model appears to be one involving Zn-GN-K-N+Znchains.231 Both nitrogen co-ordination to zinc and the disordered cyanideion models can be excluded. Of particular interest is the structure of tetra-meric methylzinc methoxide in which the zinc atoms lie a t the corners of a22s R.W. Turner and E. L. Amma, J . Amer. Chern. SOC., 1966, 88, 1877.Za6 R. W. Turner and E. L. Amma, J . Amer. Chem. SOC., 1966,88,3243.M. C. Newton and I. C. Paul, J . Amer. Ohem. SOC., 1966,88, 3161.228 N. C. Baenziger, H. L. Haight, R. Alexander, and J. R.Doyle, Inorg. Chem., 1966,P. W. R. Corfield and H. M. M. Shearer, Acta Cryst., 1966, 20, 602.2*o B. Brehler and H. Follner, N a t W s . , 1966, 53, 177.*pl A. Sequeira and R. Chidambaram, Acta Cryst., 1966, 20, 910.6, 1399GERLOCH AND MASON 725regular tetrahedron and the oxygen atoms at corners of an interpenetratingtetrahedron. This leads to four-co-ordinate zinc with oxygen atoms occupy-ing alternate corners of a distorted cube. Zn-C bond lengths are 1-94Aand Zn-0 2.09 A.232 Crystalline ethylzinc iodide is a co-ordination polymer,the iodine-zinc linkages giving rise to a layer structure.233 Each iodineatom is at a distance of 2-64 from the zinc atom lying in the same plane,the I-Zn-C angle of 144" being markedly non-linear. In addition eachiodine is 2-91 A from two other zinc atoms so that each iodine therefore formstwo long and one more normal bond to the zinc atom, which has a nearlypyramidal environment, departing considerably from tetrahedral. Themolecule of ethylzinc t-butoxide takes the form of a cube in which fourEtZnOBu are polymerised t0gether.2~~ The structure appears to bedisordered.Zinc glutamate dihydrate is nearly isostructural with the correspondingcopper c0mpound.~3~ Co-ordination about the zinc atom is nearly a regularsquare pyramid in which Zn-0 and Zn-M distances are 2.03 and 2.10~krespectively.The change in co-ordination has an appreciable effect on thedimensions of one of the carboxyl groups. A refbement of the crystalstructure of terpyridylzinc chloride has been carried The authorssuggest that the metal atom has a trigonal bipyramidal co-ordination as wasreported earlier by Corbridge and Cox. The stereochemistry has, however,been interpreted as being more approximately that of a tetragonal pyramid.137The zinc ion has a distorted tetrahedral environment in 1 ,lo-phenanthroline-zinc di~hloride.2~' The 1,lO-phenanthroline molecule is essentially planarwith the zinc atom being 0.13 A from this plane.Mean Zn-C1 and Zn-Ndistances ,are 2.20 and 2.06 8.Binuclear molecules are observed in zinc dimethylthiocarbamate.z3g Co-ordination of the sulphur about each zinc atom is distorted tetrahedral withan average Zn-S bond length of 2.36 8. Metal-metal distances in the dimersare 3-97 A. The dimethyldithiocarbamate groups deviate slightly fromplanarity and are of two types. Each group of the first type is chelateddirectly to its own zinc atom and two of the second type act as bridge ligands.An interesting comparison may be made with the copper and zinc diethyl-thiocarbamate complexes. 218Cadmium has a distorted tetrahedral environment in cadmium dibor-ate,23g with mean Cd-0 bond length 2.20 8. The structure consists of twointerlocking identical networks which are built up of a borate unit consistingof four borate polyhedra. A refinement of the structure of Cd(N03)2,4H,0is reported.240 The structure consists of tetra-aquocadmium nitrate groupsH.M. M. Shearer and C. B. Spencer, Chern. Cmnm., 1966, 194.m8 P. T. Moseley and H. M. M. Shearer, Chem. Cornrn., 1966, 876.8*4 Y. Matsui, K. Kamiya, M. Nishikawa, and Y. Tomiie, BUZZ. Ohm. SOC. Japan,lsc C. M. Gramacciolo, Ada Cryst., 1966, 21, 600.as' F. W. B. Einstein and €3. R. Penfold, Acta Cryst., 1966,20,924.m* H. P. Klug, Acta Cryst., 1966, 21, 536.m9 M. Ihara and J. Krogh-Moe, Acta Cqat., 1966, 20, 132.1966,39, 1828.C. W. Reimann, S. Block, and A. Perloff, Inwg. Chm., 1966, 5, 1185.B. Matkovic, B. Ribar, B. Zelenko, and S.W. Peterson, Ada Cryut., 1966, 21,719726 CRYSTALLOGRAPHYjoined by hydrogen bonds and the co-ordination of the cadmium atomsinvolves a distorted dodecahedron ; Cd-0 distances, from water molecules,have values of 2.26 and 2.33 A while those from the nitrate group are 2.44and 2.59A.A study has been made of mercury-oxygen distances in complexes ofmercuric chloride.241 In the adduct of azoxyanisole with mercuric chloride,the mercury ions are effectively octahedrally co-ordinated, with Hg-Cl dia-tances of 2.28 8; other contacts include three chlorines at approximately3-15 A and an oxygen atom at 2-60 A. In the 1 : 1 adduct with quinoline-N-oxide, the C1-Hg-C1 bond angles are 175", with octahedral co-ordinationof mercury being made up of two chlorines at 2-30, two oxygens at 2.56and 2-61 and two chlorines at 3.12 and 3-35.In the 1 : 2 adduct withtriphenylarsineoxide, there is a distorted tetrahedron with Hg-0 distancesof 2.32 and 2.37 8. Finally, in the 1 : 1 adduct with triphenylarsineoxide,the general conclusion is that the Hg-0 bond length is longer than thoseobtained with NO-containing ligands.In trimethylsulphonium-mercury tri-iodide, the Hg1,- ion is planar tri-gonal and the (CH,),S+ is ~yramida1.2~2 The compound dibromopyri-doxinemercury( n) chloride contains discrete C1-Hg-C1 and dibromopyri-doxine moieties.243 The Hg-C1 bond length is 2-31 A and this part of thecompound does not appear to be linear. The molecule of dichloro-(1,3,5-trithian)mercury(n) contains a distorted tetrahedron of mercury.244 TwoHg-S contacts average 2.61, two Hg-Cl, 2-44 A.The trithian molecule hasa chair conformation with the sulphur-mercury bonds being equatorial.With mercury(n), tris- (o-diphenylphosphinopheny1)phosphine and tris-(o-diphenylarsinopheny1)arsine form complexes of types [HgX,(chelate)] and[Hg(~helate)](C10,),.~~5 In the former compounds only two of the donoratoms of the quadridentate ligand are bonded to the central mercury atom,which is tetrahedrally co-ordinated. The phosphorus ligand also forms thecomplex [ HgC1( chelate)] (C10,). In bispentafluorophenylmercury, the mer-cury is bico-ordinate with an almost linear F,C6-Hg-C,F6 geometry (theangle is 176°).246 The angle between the fluorophenyl rings is 59.4".Lanthanides.-A series of rare-earth alloys with the A,B,, structure hasbeen described,247 which includes the type R2CoI7, where R represents theelements Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. Approximatemodels have been proposed for the Vaterite-type ABO, rare-earth boratesin their room-temperature and high-temperature modification^.^^^ A low-temperature model based on three-membered rings of borate tetrahedra isreconcilable with powder X-ray, optical and infrared properties.A high-temperature model containing triangular borate ions may be related to theCaCO, vaterite modification.2 4 1 A. T. McPhail and G. A. Sim, Chern. Cornm., 1966, 21.24% R. H. Fenn, Acta Cryst., 1966, 20, 20.248 F. Genet, J.-C. Leguen, and G. Tsoucarie, Compt. rend., 1966, 262, C, 989.244 W.R. Costello, A. T. McPhail, and G. A. Sim, J . Chem. SOC. (A), 1966,1190.246 G. Dyer, D. C. Goodall, R. H. B. Mais, H. M. Powell, and L. M. Venanzi, J . Chem.246 N. R. Kunchur and M. Mathew, Chem. Comm., 1966, 71.247 W. Ostertag and K. J. Sternat, Acta Cvst., 1966,21, 660.248 W. F. Bradley, D. L. Graf, and R. S. Roth, Acta Cryst., 1966, 20, 283.Soc. (A), 1966, 1110GEBLOOH AND MASON 727A correction of earlier work by Oftedal on lanthanum trifluoride hasappeared.249 The lanthanum has a normal co-ordination of nine and eachfluorine has three lanthanum neighbours. La-F distances range from2-42-30 A.A reinvestigation of the A-form of the rare-earth sesquioxide, Nd,O,shows, from symmetry and systematic absences identical to Ls203, thatthe same kind of '' micro-twinning " occurs as in the lanthanum oxide.25oThe crystal structure of neodymium tritelluride has been determined fromtwo two-dimensional projections.251 All other lanthanide tritellurides areisostructural with it.The NdTe, structure may be viewed as a stackingof NdTe unit cells with additional Te layers between cells, alternate cellsthen being shifted by a/2. The lanthanide atoms in both LaTe, and LaTe,have identical co-ordination.In a europium oxide, Eu304, both divalent and trivalent europium ionsO C C W , ~ ~ ~ the compound being isomorphous with CaFe20,. Co-ordination ofoxygens around the trivalent europium is six-fold to form a distortedoctahedron with Eu-0 distances ranging from 2.24-2.43 8.Eightfoldco-ordination around the divalent metal atoms involves each Eu2+ ion lyinga t the centre of a triangular prism of six oxygen atoms; two oxygen atomslying out from the centres of two of the prism faces complete the co-ordina-tion. The Eu-0 distances now range from 2-64-2.96 8.Actinides.-The crystal structure of thorium nitrate pentahydrate hasbeen determined by X-ray 253 and neutron 254 diffraction techniques. Thethorium is eleven-co-ordinate by three water molecules and eight oxygenatoms from four nitrate ions. All hydrogen atoms are involved in hydrogenbonds of 2.71-2.96 8. Bond lengths from the much more accurate neutronanalysis are Th-0 (water) 2.435 and 2.473 8; Th-0 (nitrate) distances rangefrom 2.528-2.618 A. The N-0 distances appear to ,vary si,anificsntlywithin the group.Potassium heptafluoroprotoactinate(v) forms infinite chains in whicheach protoactinium is surrounded by fine fluorines, two of which serve toform the chain bridges ;2s5 there is a Nd(H,O),-type co-ordination.The crystal structure of LiUF5 shows U4+ ions with nine F- ions asnearest neighbours a t distances ranging from 2.26 -2.59 A.2S6 The fluorineions Lie a t the corners of a fourteen-faced polyhedra which has the form of atriangular prism with pyramids on each of the three prism faces.TheLi+ ion has six F- ion nearest neighbours, with bond distances of 1434-2.31 A, which lie at the corners of an irregular octahedron.There have been several investigations of uranium oxides. A neutrondiffraction study 257 of cc-UO, shows it not to be hexagonal as was previouslythought. Chemical and structural arguments led to a description of a-UO,249 A.Zalkin, D. H. TempIeton, and T. E. Hopkins, Inorg. Chem., 1966,5,1466.250 H. Muller-Buschbaum, 2. anorg. Chem., 1966, 343, 6.e61 B. K. Norling and H. Steinfink, Inorg. Chem., 1966, 5, 1488.1168R. C. Rau, ActaCryst., 1966, 20, 716.863 T. Ueki, A. Zalkin, and D. H. Templeton, dcta Cryst., 1966, 20, 836.154 J. C. Taylor, M. H. Mueller, and R. I. Hitterman, Acta Cryst., 1966, 20, 842.D. Brown and A. J. Smith, Chem. Comm., 1965, 554.a66 G. Brunton, Actu Cryst., 1966, 21, 814.B. 0. Loopstra and 33. H. 9. Cordfunke, Rec. Trav. chim., 1966, 85, 135728 CEEYSTALLOCRAPHYas an imperfectly crystalline form of the orthorhombic modification generallycalled U02.9 which has an unknown structure and is disordered.Neutronand X-ray powder diffraction data show that @-UO, is a layer structure inter-connected by uranyl groups. An X-ray study of a high-pressure form ofUO, (formed a t 30 Kbar. and 1100O) has been reported.258 Each uraniumis bonded to seven oxygen atoms, leading to a shared [UO,] arrangement.Two short bonds (1.80 and 1.85 8) are nearly equal and co-linear and areidentified as the uranyl bonds. The other five form a puckered pentagonalco-ordination about the uranyl groups.259 The structure of the uranyl tri-peroxide ion is such that there is a linear UO, group with a mean U-0distance of 1-88 A surrounded equatorially by three peroxide groups a t anaverage distance of 2.27 kZs0 The mean peroxide 0-0 bond length is1-51 A. The structure is similar to those of other uranyl compounds whichhave linear uranyl groups with four, five, or more'frequently, six oxygenatoms in a plane.Calcium and strontium uranates, Ca3'hJ06 and Sr3U06, are isomorphousand may be regarded as deformed, substituted perovslrite structures.Theuranium atoms are surrounded by six oxygens at an average distanceof 2-13 8, The crystal structure of dicaesium tetrachlorodioxouranium-(VI, Cs,UO,Cl,, contains octahedral [UO,Cl,]2- ions and no seven-co-ordinate metal ions or shared ligand atoms. Caesium ions are eleven-foldco-ordinate. 2GComplexes and Organometallic Molecules of the Non-transition Elements.Group 1a.-The structures of solid hydrogen and deuterium have againbeen investigated.263 Under most conditions, D, freezes from the liquid phaseas a hexagonal close packed (h.c.p.) solid and is stable in this form againstplastic deformation.Similarly H, usually freezes in the h.c.p. form. Whengold foil with a cube texture is present, D,, normal H, and paru-H, freezein the face-centred cubic (f.c.c.) form. Plastic deformation a t about 3" and4 . 2 " ~ causes the addition of f.c.c. reflections to the h.c.p. diffraction patternsfrom samples of normal H, that previously had shown only h.c.p. Theconclusion was that normal H, is metastable in the h.c.p. structure at thesetemperatures and that spontaneous transformation to the cubic form oncooling may often be incomplete.Para deuterium, 264 in concentrationsgreater than 60%, changes from h.c.p. to f.c.c. below about 1.4"~, but below52% the h.c.p. form is stable.Lithium iodide forms an addition compound with one enclosed and fourco-ordinated molecules of triphenylphosphine oxide. &-ordination of theligand is through oxygen atoms.265 Iodide ions occupy isolated positionsat distances not less than 8.5 A from the lithium. The fdth phosphine oxideS. Siegal, H. Hoekstra, and E. Sherry, Acta Cryst., 1966, 20, 292.Ibs P. C. Debets, dcta Cryst., 1966, 21, 589.ado N. W. Alcock, Chem. Comm., 1966, 536.261 H. M. Tietveld, Acta Cryst., 1966, 20, 508.268 D. Hall, A. D. Rae, and T. N. Waters, Acta Cryst., 1966, 20, 160.C. S. Barrett, L. Meyer, and J.Wasserman, J . Chem. Phys., 1966, 45, 834.a t 4 A. F. Schuch and R. L. Mills, Phys. Rev. Letters, 1966, 16, 616.%66 Y. M. G. Yrtsin, 0. J. R. Hodder, and H. M. Powell, Chem. Comm., 1966, 706GERLOCH AND MASON 729is not bonded to any cation or anion or to any other phosphine oxide moleculeby oxygen or phosphorus but is enclosed by the rest of the structure. Adistorted octahedral arrangement of six oxygen atoms surrounds the lithiumatom in LiI0,.266 There are discrete trigonal iodate groups with 1-0 bonddistances of 1.82 8.An X-ray analysis of the " low " and " high " temperature forms ofrubidium sulphate, RbSO,, shows that, a t the transformation temperatureof 655", the change is from an orthorhombic structure to a high-temperaturehexagonal form.267 An " ion-dipole " type of structure is adopted in arubidium salt of EDTA,268 as is shown by equal (2-0 bond lengths:-OOCCH, +H,O,Rb+ >H--(CH,) 2-~€€<cH2c0 Rb+,H,O-OOCCH, CH,COO-A structural analysis of Cs1,Br shows it to be isostructural with C S I , .~ ~ ~In CsI,Br, the Br-I distance is 2.906 8; 1-1 is 2.77 A and the angle Br-1-1is 178".Group IIa.-The structure of Li,BeF,270 is isotypic with that of Be,SiO,.The beryllium ion is tetrahedrally co-ordinated with a mean Be-F bondlength of 1.55 8. The lithium is also tetrahedral and there are two types ofLi-Li contact, being 1-86 and 1.88 A. In calcium beryllate, Cal,Bel,O,,,there are two types of oxygen co-ordination: octahedral and one in whicheight oxygen atoms form a rectangular pri~m.~71 Three types of berylliumco-ordination are apparent : a normal tetrahedron, a distorted tetrahedronconsisting of t h e e short and one long Be-0 bond, and a very unusualtrigonal arrangement of the beryllium by oxygen.The magnesium ions in MgCl,,12H20 are octahedrally co-ordinated bywater molecules as are the chloride i0ns.~'2 The ionic bonded cationicoctahedra are regular while the larger hydrogen-bonded anionic octahedraare considerably distorted.The mean Mg-0 value is 2-06A while C1-0distances range from 3.11-3.26 8.Calcium ions are also octahedrally co-ordinated by water molecules in thestructure of CaBr2,10H,0~2(CH2),N,.273 The hexamethylene tetraminemolecules are hydrogen-bonded to water.In strontium cyanamide, the structure consists of strontium and linearcyanamide ions in which the anions are probably either rotating or statistic-ally distrib~ted.~'~Each barium ion is ten-co-ordinated by four water molecules and sixoxygen atoms from six different dithionate groups in barium dithionate&hydrate, BaS,06,2H20 ;275 Ba-0 bond lengths range from 2.67-3-12 b.266 A.Rosenzweig and B. Morosin, Acta Cryst., 1966, 20, 758.267 G. Pannetier, D. Tabrizi, and M. Gaultier, Bull. SOC. cham. France, 1966, 1273.268 M. Cotrait, Compt. rend., 1966, 263, C, 55.G. B. Carpenter, Acta Cryst., 1966, 20, 330.270 J. H. Burns and E. K. Gordon, Acta Cryst., 1966, 20, 135.871 L. A. Harris and H. L. Yakel, Acta Cryst., 1966, 20, 295.K. Sasvari and G. A. Jeffrey, Acta Ctyst., 1966, 20, 875.273 P.De Santk, A. L. Kovacs, A. M. Liquori, and L. Mazzarella, J . Amer. Chem. Soc.,874 K.-G. Strid and N.-G. Vannerberg, Acta Chem. Scad., 1966, 20, 1064.*'ti J. A. Rausell-Colom and S. Garcia-Blanco, Acta Cry&., 1966, 21, 672.1965, 87, 4965730 CRYSTALLOGRAPHYI n barium diethylphosphate, the diethylphosphate anion has a configurationin which two G O bonds lie in the gauche positions with respect to theP-0 which is in agreement with spectroscopic data on an aqueoussolution of barium dimethylphosphate. The angles of internal rotationaround the G O and P-8 bonds are compared with those of tlhe proposedmodels for nucleic acids and synthetic polynucleotides.Group IIlb.-Successful refinements of the structures of B,CI,, B4€€,,,Bl8H22, B8H11, B&,H8, Bl,C2H,C18, and BloHlo( CCH,Br), have been re-ported.277 Molecular and crystal structures have also been determined 278of o-B,,,Br,H,C,H,, o-B,,Br,H,C,H,, and o-B,,Br,H,C,(CH,), (19).In thedibromocarborane the bromines are in the 9- and 12-positions, exactlyopposite the two carbon atoms. Thus, the bromine atoms are on adjacentcarbons and the molecular symmetry is CZv. Molecular orbital argumentssuggest that electrophilio substitution has taken place. The structure ofY. Kyogoku ahd Y. Iitaka, Acta Cryst., 1966, 21, 49.G. S. Pawley, Acta Cryst., 1966, 20, 631.a78 J. A. Potenza and W. N. Lipscomb, Inorg. Chem., 1966, 5, 1471, 1478, 1453GERLOCH AND MASON 731BQC2HQMe2 represents the first example of a carborane in which carbon atomswithin the cage fragment are non-vicinal.279 The carbon atoms in the 6-and 9-positions have methyl substituents.A new classification of cagestructures is presented by the structure of B20H,6(NC*CH,)2,CH3CN.280One of the three acetonitrile units is isolated from the rest of the moleculewhich has two very nearly linear acetonitriles linked in terminal positions toboron atoms. The boron atom rearrangement has yielded a B1, icosahedronwhich shares a triangular face with a B,, icosahedral fragment. A singlebridge-hydrogen atom occupies the open pentagonal face of the B,, fragment.The similarity between the appropriate parts of B20H1,(NH*CH3)2 and theB,C2Hl,- ion leads the authors to propose that boron hydrides, composed oficosahedra sharing a triangular face, be generally called polyicosahedralboranes.A detailed neutron diffraction analysis has been made of orthoboricacid, D,llBO,.”l The coherent neutron scattering length for llB has beendetermined. The 0-D-0 bond lengths are 2-71 A and the hydrogen bond isessentially linear. The high-temperature form of barium borate, BaO,B,O,,contains nearly planar (B306)3- ion groups constructed of three BO, triangles,each of which shares two of three corners.282 The bariums are co-ordinatedby oxygens in a trigonal prismatic way with the barium having a nine-foldco-ordination.In the (B30JS- anion ring, the B-0 ring bond lengths are1.40 A, the exocyclic values being 1.32 A. The structure of LiB(OH), con-sists of B(OH), tetrahedra linked to LiO, tetrahedra by common edges andby asymmetric hydrogen bonds; 283 the hydrogen atom positions have beendetermined directly.The bond lengths are B-0 1.48, Li-0 1-97, and0-H 1-05 A; the 0 H distance is 1-89 8. Molecules of dimethylamino-boron difluoride are dimeric with DZh symmetry, and consist of four-mem-bered (BN), rings with substituents above and below the plane of the ring.284The methyl groups are fully staggered with respect to the B-N-B framework.A Zow-temperature analysis of the crystal structure of borohydridetri-methylaminealuminium shows that the aluminium atom has a distortedpentagonal bipyramidal co-ordination ; the pentagonal plane is defined byfive bridging atoms and the two apical positions are filled by a secondbridging hydrogen and by nitrogen of the trimethylamine d0nor.~8~ Theresults of three-dimensional single-crystal structure analyses are reportedfor m4C3, Al,C,N, m6C3N2, and Al,C3N4.286 Carbon atoms are five- and six-co-ordinated to the nearest neighbour aluminium atoms.An X-ray andtwo-dimensional neutron difia ct ion analysis of Cs Al (S 0,) , 1 2H20, shows 287that in this b-alum, the aluminiums are co-ordinated by six water moleculesa t an Al-0 distance of 1.88s; the caesium is co-ordinated by six water-C. Tsai and W. E. Streib, J . Amer. Chem. Soc., 1966, 88, 4513.J. H. Enemark, L. B. Friedman, J. A. Hertauck, and W. N. Lipscomb, J . Amer.Chem. SOC., 1966, 88, 3659.**l B. M. Craven and T. M. Sabine, Acta Cryst., 1966,20, 214.%** A. D.Mighell, A. Perloff, and S. Block, Ada Cryst., 1966, 20, 819.tssE. Hohne, 2. anorg. Chem., 1966,342, 188.A. C . Hszell, J . Chem. SOC. ( A ) , 1966, 1392.*86 N. A. Bailey, P. H. Bird, and M. G. H. Wallbridge, Chem. Comm., 1966, 286.G. A. Jeffrey and V. Y. Wu, Acta Cryst., 1966, 29, 638.D. T. Cromer, M. I. &y, and A. C. Larson, Actcr Cryst., 1966, 21, 383.732 CRYSTALLOGRAPHYoxygen atoms a t 3-37 8, and six sulphate-oxygens a t 3-45 8. In dibromo-trimethylsiloxyaluminium,2s8 the molecule is dimeric with two M-Br,groups bridging two siloxy-groups. The aluminium ion is five-co-ordinatein an aluminosiloxane structure.289 The co-ordination geometry is that of a,distorted trigonal bipyramid or distorted square pyramid, the mean Al-0distance being 1.86 and the Al-Br 2.25 8.The high-pressure synthesis andcrystal structure of a-LiAlO, have been des~ribed.~~a The a-form is pre-pared as a metastable phase by subjecting y-LiAlO, to 35 kbar. a t 850"and then quenching to room temperature and pressure. The a-phase con-tains octahedrally co-ordinated cations while those in the y-phase are tetra-hedral. This dimorphism is similar to that in LiGaO,. Average Li-0 andAl-0 distances are 2.12 and 1.90 8, respectively. In potassium aluminate,K,[Al,O(OH)J ,291 discrete aluminium oxygen groups [ (OH),Al-O-Al( OH)J2-occur, built up from two AlO, tetrahedra sharing an oxygen. These groupsare then held together by potassium ions.In magnesium gallate, MgGa,O,, the magnesium ions are distributedbetween two sites, 16% in tetrahedral and 81% in the remaining octahedralsites.292 The structure of a hydrated gallium phosphate of compositionGaP0,,2H20 may be regarded as [Ga,(OH)(H,O,)] (H20)(H)(P04)2.293 The[Ga,(OH)(H,O,)] atoms form an infinite double chain complex and threechains connect surrounding phosphates through gallium and water-oxygenbonds to give a channelled three-dimensional network.The galliums aresix-co-ordinate with a mean Ga-0 bond length of 1-99 8. Edge-sharing ofadjacent octahedra gives a Ga-Ga distance of 3-06 8, while other such dis-tances have a minimum value of 3.75A.The refinement of the crystal structure of In,O, using two differentX-radiations has been made. 294 The two crystallographically non-equivalentindium atoms in the unit cell are both six-co-ordinate; the first has sixequidistant oxygen atoms with a mean In-0 distance of 2.188, while thesecond has a different form of six-co-ordination involving three different setsaf In-0 distances ranging from 2-13-2.23 8.At room temperature, indiumchloride has a deformed sodium chloride structure with twelve indium ionssurrounding a given indium cation, arranged so that three are much nearerto it than the other nine; the mean distances are 3-65 and 4-70 k respec-tively. 205A detailed structural analysis 296 of T1N03,4(thiourea) has been reportedas part of a more general study of ionic complexes of thiourea. Separatecations and anions are bridged by polar thiourea molecules. Each cation issurrounded by eight sulphur atoms a t the corners of a distorted cube, themean Tl-S distance being 3*43k, considerably longer than the separationbetween sulphur atoms of co-ordinated ligands and metal atoms.TheM. Bonamico, G. Dewy, and C. Ercolani, Chern. Comm., 1966, 24.M. Bonamico, Chem. Comm., 1966, 135.M. Marezio and J. P. Remeika, J . Chm. Phys., 1 9 6 6 , s 3143.2n1 GF. Johannaon, Actu Chem. Scund., 1966, 20,606.2Q8 J. E. Weidenborner, N. R. Stemple, and Y. Okays, Actu CV8t., 1966, 20, 761.m a R. C. L. Mooney-Slater, A& Cr?/st., 1966, 20, 526.294 M. Marezio, Actu Cqst., 1966, 20, 723.J. M. van den Berg, Acta Cryst., 1966, 20,905.996 J. C. A. Boeyens and F. H. Harbstein, Nature, 1966, 211, 588GEBLOCH AND MASON 733structure of T1C104,4( thiourea) is also reported together with a discussion ofother related thallium molecules.Group IVb.-The cubic phase of ammonium fluorosilicate involves three-fold, probably dynamic, disorder of the ammonium groups. In the trigonalphase,207 there is probably two-fold disorder of these groups and because ofthis and also large thermal motions, the precise location of the hydrogenatoms was not possible.In the crystal structure of Na20,Si0,,9H20, thesilicon atoms are tetrahedral with oxygen at 1-67 and 1-59 Each sodiumion is co-ordinated by six oxygen atoms a t the corners of a distorted octa-hedron. Bond lengths range from 2.41-2-508. In the structure ofNa,H,Si04,4H20, isolated SiO, tetrahedra linked by hydrogen bonds formlayers which are separated by sodium ions and water molecules.299 A struc-tural analysis has been completed of a-naphthylphenylmethylsilane and isof particular interest in so far as it allows the absolute configuration deter-mination of several optically active silicon compounds.300 The overcrowdingaround the asymmetric silicon atom is demonstrated by the non-planarityof the naphthyl group.The structural analysis of the dehydrated tetramer of 1 ,%dimethyl-disilanetetraol shows that the skeleton of the molecule consists of two crown-shaped SiO, rings which are crystallographically independent and connectedby four silicon-silicon bonds.301 The four six-membered (SiSi), rings thusformed have boat shapes so that the molecule has a cage-like structure withan approximate symmetry of 4/mm?n.The S i S i distance is 2-36 8, Si-0ranges from 1-63-1-67 A, and Si-C from 1*84-1*92 A.An analysis of neptunite shows a new three-dimensional network of SiO,tetrahedra and suggests a new formula for the material.302 In ekanite,ThK(Ca, Na)&3i,02, eight SiO, tetrahedra share three corners each to forma " crown " of two rings of four tetrahedra.303 Bavenite, having the formulaCa,(BeOH)2+,J12--3cSi9026--z has again been assigned a new formulation onthe basis of the determination of the hydrogen atom positions.304 Oxygenand silicon positions in the mineral eulytite, Bi4Si30,,, have been determinedby neutron diffraction.305 The mineral consists of irregularly co-ordinatedbismuth ions which link discrete SiO, tetrahedra.Germanium dsuoride is a fluorine bridged chain polymer in whichparallel chains are cross-linked by weaker fluorine bridges.The structuralunit of the strongly bridged chains is a trigonal bipyramid of three fluorineatoms and an apical germanium atom with Ge-F distances of 1.79, 1-91and 2.098; the angles F-Ge-F are 85-0, 85-6 and 91.6". The two longerbonded fluorine atoms are structurally equivalent and join each germaniumatom to its two neighbours in the chain. The fluorine atom 1-79 A distant2s7 E. 0. Schlemper and W. C. Hamilton, J . Chem. Phyg., 1966, 45, 408.2s8 P. B. Jamieson and L. S. D. Glasser, Acta Cryst., 1966,29, 688.esD K.-H. Jost and W. Hilmer, Acta Cryst. 1966, 21, 683.300 Y. Okaya and T. Ashida, Acta Cryst., 1966, 20, 461.301 T. Highchi and A.Shimada, Bull. Chem. Soc. Japan, 1966, 39, 1316.808 F. Cannillo, F. Mazzi, and G. Rod, Acta Cryst., 1966, 20, 200.803 V. I. Mokeeva and N. I. Golovastikov, Doklady Alcad. Nauk S.S.S.R., 1966,167,804 F. Cannillo, A. Coda, and G. Fagnani, Acta Cryst., 1966, 20, 301.* 0 6 D. J. Segal, R. P. Santoro, and R. E. Newnham, 2. Krist., 1966,123, 73.1131734 CRYSTALLOGRAPHYfrom each germanium atom makes a weak bridge point with a germaniumatom in an adjacent chain 2-57 A away from the fluorine. The geometry ofthe GeF, group is consistent with the steric activity of the non-bondingvalence electron pair ; it may be described as a distorted bipyramidal arrange-ment of four fluorine ligands and an equatorial electron pair.30g Lithiumdigerminate, Li,Ge,05, has a layer structure and is isostmctural withLi@,05.307 Molecules of trimethylcyanogermane have Ca0 symmetry withinexperimental error, Ge-C (methyl) bond lengths being 1-98 A and the samefor Ge-C (cyanide).The cyanide G N bond lengths average 1.15~.s0sIn Na,SxiE",, the tin has a distorted octahedral co-ordination with pairsof SnF, distances of 1.83, 1.92 and 1-96 Octahedral co-ordination oftin is also evident in the structure of dimethyltin difl~oride.~lO The struc-ture consists of an infinite two-dimensional network of tin atoms andbridging fluorine ions with the methyl groups above and below the planecompleting the octahedral co-ordination. Sn-C distances are 2.08 andSn-I?, 2-12 A. In trimethyltin cyanide 311 the structure consists of planar(CH,),Sn groups with approximate D,h symmetry, and disordered cyanidegroups symmetrically disposed on either side of these groups.Interatomicdistances for Sn-C (methyl), Sn-C (or -N) cyanide, and G N are 2.16, 2.49,and 1.09 A, respectively.The lead ions in lead thiocyanate are six-co-ordinate via two sulphurand four nitrogen atoms.312 There are, apparently, two more sulphur atomsa t slightly greater distances from the metal. The Si,O, group in varysilite,MnPb,,3Si20,, is not linear, the Si-0-Si angle being 133'. Each lead isco-ordinated by oxygen atoms.313 A slightly distorted octahedral environ-ment for Pb2f ions is evident in lead hexn-antipyrine per~hlorate.3~~ The-- - ______ _____________- - -. __30*."J. Trotter, M. Akhtar, and N.Bartlett, J . Chem. S O ~ . ( A ) , 1966, 30.307 E. Modern and A. Wittman, Monatsh., 1965, 96, 1783E. 0. Schlemper and D. Britton, Inorg. Chem., 1966, 5, 511.30D C.iHebecker, H. G. von Schering, and R. Hoppe, Natumok8., 1966, 53, 164.slo E. 0. Schlemper and W. C. Hamilton, Inorg. Chem., 1966, 5 , 995.E. 0. Schlemper and D. Britton, Inorg. Chem., 1966, 5, 507.313 J. A. A. Mokiolu and J. C. Speakman, Chem. Comm., 1966, 25.213 J. Lajzerowicz, Acta Cryst., 1966, 20, 357.314 M. Vijayan and M. A. Viawamitra, Acta Cwst., 1966, 21, 522GERLOCH AND MASON 735average of the six Pb-0 bond lengths is 2.45 8. The five-membered pyrazolering is planar and makes an angle of 68" to the phenyl ring. C1-0 distancesin the perchlorate are 1-45A.In ethylxanthatelead, the two xanthate groups are bonded to the leadion by the dithiocarbonic ends.3l5 The molecule is non-planar althougheach xanthate group is planar.A chain structure (20) is found in the ortho-rhombic modification of dicyclopentadienyl-lead, in which there are bothbridging and normal n-type cyclopentadienyl rings.316 The bridging ring issituated midway between two lead atoms at a mean Pb-C distance of3.06 8. The mean Pb-C (other z-Cp ring) is 2.76 8. The ligand planes areinclined at 121" and 118" to each other and the metal-to-ring-centre vectorsare coplanar, suggesting an .sp2 hybridisation state for the lead atoms.Vb.-In tetramethylammonium hydroxide pentahydrate, thehydroxide ion and water molecules form a hydrogen-bonded frameworkbased on a space filling arrangement of truncated octahedra.317 Equivalent(CH3),N+ ions occupy the full available polyhedral cages in the unit celland distort the cubic symmetry from the idealised oxygen 1at)tice formedfrom undistorted face-sharing truncated octahedra. The framework of thehydrate is closely similar to that found 318 in the acid hydrate HPF6,6H,0.In dihydrazinium sulphate, the N-N distance in the hydrazinium ions is1.43 A.The structure is extensively hydrogen-bonded.In mixed crystals of P,O, and P407, the molecules differ from the usualP,Ol, molecules by two and three missing terminal-oxygen a t o m ~ . ~ l ~ Thegeometry of the P40s molecule has been discussed in some detail. A newseries of acidic compounds of HF'P,O, and H,XIVP,O,, (where Xv is As orSb and XIv is Si, Ge, Sn, Pb, Ti, and Zr) have been studied.320 The arsenic(v)-phosphorus(v) compound HAsP,08 has a layer structure built up by AsP,O,layers with inter-layer protons (which may be exchanged by other cations).HSbP,O, is isomorphous with HAsP,O,.The H,XIVP,O, compounds haveanalogous layer structures and ion exchange properties. There are three equalP-0 bond leng t ha in dipot nssiurn phenylp hosp hat e , I.,C,H,P 0, ,3/2H,O,the fourth being involved with the phenyl group. The F;tructural analysisof p-bromophenyldiphenylphosphine has given a mean P-C bond lengthequal to 1-83 The triclinie form of phosphobenzene involves both six-membered phosphorus rings in the chair configuration with phenyl groupslying in the equatorial positions.323 The molecule of 1,2,3-triphenyl- 1,2,3-tri-phospliaindane has exact C, symmetry, the phenyl group in the 2-positionbeing trans to those in the 1- and 3-positions and also lies in the molecularmirror plane.324 The bicyclic phosphaindane nucleus contains a new typeGroup816 H.Hagihara and S. Yamashita, Actu Cryst., 1966, 21, 350.a17 T. K. McMullan, T. C. W. Mak, and G. A. Jeffrey, J . Chem. Phys., 1966,44,2338.318 R. Liming& and J. 0. Lundgren, Acta Chem. Scad., 1965,19, 1612. R. Lirninga,820 A. Winkler and E. Thilo, 2. anorg. Chem,., 1966, 346, 92.8aa H.-J. Kuhn and K. Plieth, Naturw'ss., 1966, 53, 359.a2a J. J. Daly, J . Chem. SOC. ( A ) , 1966, 428.824 J. J. Daly, J . Chem. Soc. ( A ) , 1966, 1020.C.Panattoni, G. Bombiori, and U. Croatto, A4cta Cryst., 1966, 21, 823.&id., p. 1629.K.-H. Jos~, Acts C ~ s t . , 1966, 21, 34.Mazhar-ul-Haque and C. N. Caughlan, Chem. Comm., 1966, 669736 CRYSTALLOGBAPHYof five-membered ring and is roughly planar. The five-membered ring isCCPPP. Apparent attraction between the lone pair on the phosphorus atomand a hydrogen atom from a neighbouring phenyl group leads to a certainsteric effect.The structure of a ten-membered phosphorus-nitrogen ring is shown in astructural analysis of (NPC12),.325 The PN ring is very nearly planar withC1-P-C1 and N-P-N angles very close to those found in trimeric and tetra-'meric phosphonitrilic rings. The P-N distances range from 1.49-1-55 &the mean, 162& being considerably shorter than that observed in thetrimer (1.59 8) or the tetramer (1058 8).In the pentamer the P-N-P bondangle is 148", 16" greater than that in the tetramer. The suggestion is madethat mbond character between phosphorus and nitrogen increases with in-creasing ring size. In dimeric N-methyltrichlorophosphinimine, the four-membered ring contains alternating phosphorus and nitrogen atoms, thephosphorus atom being trigonal bipyramidally co-ordinated by three chlor-ines and two nitrogen^.^^^ One nitrogen is axial and the other equatorial,so that two different P-N and P-C1 contacts range from two of 2.02 to oneof 2-15 A. Again the suggestion is made that the P-N bond lengths indicatepz-dz bonding. This structure has been independently determined byHoard and Jacobsen 327 to give identical results within experimental error.The analysis of the benzenetris( o-pheny1enedioxy)phosphonitrile trimer con-tains (CH,O),P(S)-S-Te-S-(S)P(OCH,), units with tellurium atoms ondiads.328 The molecule contains a PS-Te-S-P chains in the trans form withan STe to TeSP dihedral angle of 90.7".The Te-S distance is 2.44 8, withP-S contacts of 2-09 and 1-92A. The crystal structure of 2,2-dichloro-4,4-6,6-tefraphenylcyclotriphosphazatriene shows the cyclotriphosphazinering to have a slight boat form in contrast to the slight chair form found inthe diphenyltetrachloro-compound.329 Three sets of P-N bonds are 1.556,1-578, and 1-609 A. The exocyclic Cl-P41 angles are 98.5"; angle C-P-Cis 104.4", two N-P-N angles are 120.7 and 115.5", and P-N-P angles are1214 and 124.9 ". The structure of octamethoxycyclotetraphosphazate-traene shows that the molecule is very close to the ideal saddle shape, with~1 mean P-N bond length of 1.57 and P-0 of 1 0 6 0 8 .~ ~ ~The structure of As,0,,5/3H20 consists of spiral chains formed by linkedBSO, tetrahedra and AsO, octahedra.331 The tetrahedral bonds average1-69 while those in the octahedron range from 1*76-1*87 8. The arsenicatom is effectively pyramidal in methyldicyanoarsine. 332 The As-C distanceis 1-98A to the cyanide, and 2.00A to the methyl group; As-C-N anglesare 175". Arsenic is tetrahedral with a mean As-C bond length of 1-90 Ain t e traphenylarsonium- 3 -fluoro - 1,1,4,5,5 -pent a c yano - 2 - azapent adienide .The carbon ion in this complex is non-planar.A novel arsenic co-ordination325 A. W. Schleuter and R. A. Jacobsen, J. Amer. Ghem. Soc., 1966, 88,2051.826 H. Hess and D. Forst, 2. anorg. Chem., 1966, 342, 240.828 G. W. Smith, D. Wood, and S. Husebye, Acta Chem. Scad., 1966, 20, 24.329 N. V. Mani, F. R. Ahmed, and W. H. Barnes, Acta Cryst., 1966, 21, 376.930 G. B. Ansell and G. J. Bullen, Chem. Cmm., 1966, 430.831 K.-H. Jost, H. Worzala, and E. Thilo, Acta Cryst., 1966, 21, 808.332 E. 0. Schlemper and D. Britton, Acta Cryst., 1966, 20, 777.888 G. J. Paler&, Acta Cryst., 1966, 20, 471.L. G. Hoard and R. A. Jacobsen, J . Chem. SOC. ( A ) , 1966, 1203QERLOOH AND MASON 737is reported in the structure of potassium di-o-phenylene-dioxyarsenate(m)where the Asm is a distorted trigonal bipyramid.334 Two As-0 bonds are1.81 and two 2.008.The structures of antimony and bismuth iodides illustrate the increaseof ionic character in the bonds on progressing down the group.335 Thus,antimony atoms are significantly displaced from the centres of iodine octa-hedra, having three Sb-I contacts of 2.686 and three of 3.316 8; the structureis intermediate between the molecular crystal of Ad3 and a completely ionicsystem.In contrast, bismuth does Lie at the centre of an octahedron ofiodine atoms, indicating the lack of any steric activity of the non-bondingelectron pair in this largely ionic structure. The antimony ions in ammoniumhexabromoantimonate are six-co-ordinate and form a distorted K,PtCl,structure in which the ions are arranged in an ordered array with likeoxidation states of antimony repeating along the a and b unit cell directions,but alternating along the c directi0n.33~ The (sb111Br,)3- ions are undis-torted but the SbVBr,- ions are distorted.The average Sb-Br bond lengths€or the +3 and +5 oxidation states are 2.80 and 2.568, respectively.Octahedral co-ordination of antimony by five chlorine atoms and thecarbonyl-axygen atom of NN-dimethylformamide has been observed inSbC15,HCON(CH3)2.337 Sb-C1 distances average 2.33 and Sb-0 2.05 8.The crystal structures of pyridinium salts of PF,-, AsF,- and SbF,- ionshave been detem1ined.33~ Within experimental error, the phosphorus,arsenic and antimony atoms are all octahedrally co-ordinated with P-F,As-F and Sb-F distances of 1-59, 1.78, and 1.87 8 respectively.Triphenylbismuth dichloride and triphenylbismuth are such that themolecules are trigonal bipyramids, the bismuth atom and carbon atoms towhich it is bonded lying in a plane with the bismuth+hlorine bonds axialto it.==Group VIb.-The molecular parameters-bond distances, bond angles,and dihedral angles-of fibrous sulphur are compared with those of othersulphur rn01ecuIes.~~~ In a-sulphanuric chloride, a- (NSOCl),, the sulphanuricchloride exists in the chair form with the chloride atoms in axial positions.341The short S-N bond length of 1-57A indicates p,d, bonding.The in-organic heterocycle, cyclopentathiotri-imine, S5N3H,, is an eight-memberedpuckered ring in which the hydrogen atoms are readily replaceable byorganic The ring possesses an exact mirror plane perpendicularto the mean plane of the ring.Sulphur-carbon and selenium-carbon dis-tances have been determined 343 from the isotypic molecules, S(CN), andSe(CN),; S-C distances are 1.87 and 2.07 A with G N distances of 1.02 andm A. C. Skapski, Chem. Cmm., 1966,lO.386 J. Trotter and T. Zobel, 2. Krkt., 1966, 123, 67.3s6 S. L. Lewton and E. A. Jrscobsen, Inorg. Chem., 1966, 5, 743.ss7 L. Brun and C.-I. Branden, Acta Cryst., 1966, 20, 749.R. F. Copeland, S. H. Comer, and E. A. Meyers, J . Phy8. Ohm., 1966,70,1288.a39 D. M. Hawley, G. Fergueon, and G. S. Harris, Chem. C m . , 1966, 111.s40 F. Tuinstra, Acta Cryst., 1M6, 20, 341.s41 A.C. Hazell, G. A. Wiegers, and A. Voe, Actu Cryst., 1966,20,186. G. A. Wiegers34a H. Garcia-Fernaradez and C. Rerat, Cmpt. r e d . , 1.966, 282, C, 1866,84a K.-H. Linke and F. Lemmer, 2. Naturfmsch., 1966,21b, 192.and A. Vos, ibid., p. 192738 CRYSTALLOGRAPHY1*20A, S e C contacts are 2.08 and 2.01 A with G-N bonds of 1.07 and1-27 A. The angles C-S-C and G-Se-C are 96 and 99", respectively. Amolecular structure analysis 344 of dimethyl sulphoxide shows that themolecule has C, symmetry, within experimental error. Mean distances areS-0 1-53 and S-C 1 4 0 k The angles O-S-C and G-S-C are 106.7 and97.4". An independent analysis 345 gives a rather different value for theS-0 bond length. The hexathionate ion occurs as the cis-cis rotationalisomer in potassium barium h e ~ a t h i o n a t e .~ ~ ~ The average S-S bond lengthis 2.05 A and S-S-S angles range fiom 101-113". The ion has approximateC2 symmetry.The selenium ion in magnesium selenite hexahydrate is pyramidal withan Se-0 distance in the (Se0,)2-ion of 1.69 A.347 The structure of trimethyl-selenonium iodide, Me,SeI, is built up of groups of selenium and iodide ionswith a linear GSe*-I arrangement.348 Mean distances for Se-C and Se-Iare 1-96 and 3-78A. The G-1-Se bond is linear in 1,4-diselarhetetra-iodoethylenei~dine.~~~ The iodine is bonded to two selenium atoms. Bis-(diethylthiophosphory1)diselenide contains an Se-Se bond length of 2.33,with Se-P equal to 2-28 and P-S to 1-93 A.350 The dihedral angleP-Se-Se/Se'-Se-P is 105 '.In the iodine complex of l-oxa-6selenacyclo-hexane, the six-membered ring is in the chair configuration with the iodinemolecule bonded to the selenium in the axial position.351 The Se-I bondlength of 2.76A is very short. Selenium also forms a weaker bond withthe second iodine molecule of length 3-71 A.Diammonium hexachlorotellurate(rv) has the K,PtCl, structure in whichthe TeC1,2- ion is a regular octahedron;35a Te-C1 is 2.54 8. (NH4),TeBr,and Cs,TeBr, also have the K,PtCl, structure, the Te-Br distances in theoctahedral tellurium being 2.70A in both crystals.553 The structure ofbasic tellurium nitrate, Te20,,HN03, consists of puckered layers of telluriumand oxygen atoms with each tellurium atom linked to one other by twooxygen bridges, and to two others by single oxygen bridges.ss4 Fourtellurium-oxygen bonds around a tellurium atom are directed approximatelytowards the axial and two equatorial apices of a trigonal bipyramid; TeOdistances range from 148-2.16 8.The nitrate group is hydrogen-bondedto one of the bridging oxygen atoms. Tellurium(1) has a trigonal bipyramidalgeometry in the Te,O, group of Zn,Te,0,.865 The group is built up ofTeIO, and TeIIO, units in which the Ten is pyramidal. TeI-0 distances are1.83 and 2-108, while TeII-0 contacts are 1.98, 2.41, 1-93, and 1-888.Thiourea complexes of tellurium dichloride and dibromide have been844 R. Thomas, C. B. Shoemaker, and K. Erika, Acta Cryst., 1966,21, 12.8413 0. Foss and K. Johnsen, Acta Chem Scad., 1966, 19,2207.847 R.Weiss, J.-P. Wending, and D. Grandjean, Acta CTyst., 1966, 20, 663.a48 H. Hope, Acta Cryat., 1966, 20, 610.84g T. Dahl and 0. Haasel, Acta Chem. Scand., 1965, 19, 2000.S. Husebye, Acta Chem. Stand., 1966, 20, 51.Ss1 H. Maddox and J. D. McCullough, Inorg. Chem., 1966, 5, 622.ssa A. C. Hazell, Acta Chern. Scand., 1966, 20, 165.863 A. K. Das and I. D. Brown, Canad. J . Chem., 1966,44,939.~m L. N. SwinIr and G. B. Carpenter, Acta Cryat., 1966, 21, 678.866 K. Hanke, NQlu&8., 1966, 63, 273.M. A. Viawamitra and K. K. Kannan, Nature, 1966, 209, 1016GERLOCH AND MASON 739studied.356 Each tellurium ion is bonded to two sulphur and two halogenatoms in a distorted square planar cis arrangement. Bond lengths are:T e a , 2-48; Te-Cl, 2-92A; and Te-Br, 3.05h.Both the Te-S bonds meshorter and the Te-halogen bonds longer than in t,he corresponding trans-tellurium@) complexes. In phenylbis(thiourea)tellurium(n)each tellurium atom is bonded to a phenyl carbon atom and two thioureasulphur atoms. Bond distances are Te-C, 2.11 and T e a , 2-61 and 2.74 A.The structure may be regarded as a square planar co-ordination with onevacant position, trans to the phenyl group. The crystals of bis(dimethy1-dithiophosphate)tellurium are built up of (CH,O),P(S)S-Te-S-S(P) (OCH,),molecules. Details have been given above. There is a tendency towardssquare planar co-ordination around the tellurium. Complexes of benzene-tellurenyl chloride and bromide with thiourea have been Thetellurium atoms are bonded to one phenyl carbon atom and, in directionsapproximately normal to the Te-C bond, to one thiourea sulphur atom andone halogen.T e a , Te-C, and Te-C1 distances are 2-50? 2.12, and 340Arespectively. The fourth position of the square planar tellurenyl co-ordina-tion is occupied by another halogen atom which is, however, 0.7 A furtheraway than the other halogen.Group VIIb.-The compound, CsCl, 2/3HC1, 1/3H20, has been reformu-lated on the basis of an X-ray crystal structure analysis asCsC1,1/3(H30+, HCl,-) .359 Most chlorine-chlorine distances throughout thecrystal are 3.6 A or more and, as such, typical of van der Waals contacts,but one is almost 0.5 shorter, at 3-14 A and is identified as belonging to thedichloride ion, HC1,-. Oxygen-chlorine distances are 2.92 and 2-95 A whileczesium is nine-co-ordinate with Cs-Cl ranging from 3-44 to 3-70A.A list of oxygen-iodine, sulphur-iodine, and selenium-iodine distanceshas been compiled and a discussion of complexes involving these bondsmade.The effect of pressure on the lattice parameters of iodine, stanniciodide, and p-di-iodobenzene has been e~amined.3~0 All three have a largecomponent of van der Waals binding and each exhibits a compressibilitywhich decreases with increasing pressure. On the basis of the estimatedchange of distances in the crystal, the approach to the metallic state in andperpendicular to the ac plane in iodine is explained. The approach to themetallic state and possible bond deformation in SnI, is also discussed.Orthoperiodic acid, H5106, and anhydro-iodic acid, H130, have been studiedby neutron and X-ray diffraction, respectively.361 The molecule of H510,consists of a slightly deformed 10, octahedron, five of the oxygen atoms ofwhich are directly linked to hydrogen.362 For these five oxygen atoms, thedistance to the central iodine is 1.89 A, the remaining oxygen being closer,at 1-78 A.H130B consists of HIO, and 120, units with strong intermolecularzib6 0. FOBS, K. Johnsen, I(. Maartmann-Moe, and I(. Maray, Actcr Chem. Scand., 1966,90, 113.8b7 0. Foss and K. Maray, Acta Chem. Scand., 1966, 20, 123.as* 0. Foss and S. Husebye, Acta Chem. Scand., 1966,20, 132.*6s LeR. W. Schroeder, and J. A. Ibers, J . Amer. Chem. SOC., 1966,88,2601.m0 0. Hassel, Acta Chem.Scand., 1965, 19, 2259.a1 R. W. Lynch and H. C. Drickamer, J . Chem. Phys., 1966,45, 1020.m* Y. D. Feikama, Acta Cryst., 1966, 20, 765; Y. D. Feikama and A. Voe. ibicE.,p. 769740 URYSTALLOGRAPHYiodine-ozrygen interactions. The 1,05 group has four iodine-oxygen bondsof 1-79 and one of 1-96 8. The length of the two double bonds in the(HO)(IO,) group is 1.80 A with the 1-0 single bond lengths being 1-90 8.2. OBGANIC STRUCTURESAliphatic Molecules.-The first structural analysis has been completedof an oxocarbonium ion through the crystal structure determination 363 ofCE3CO+,SbF6-. The G C bond distance of 1-38A is much shorter thanvalues in isoelectronic species CH,CiN and CH3CiCH. The carbon-oxygenbond length is close to that in carbon monoxide itself.In methane sul-phonamide the central sulphur atom is a slightly distorted tetrahedron, theC-S bond length is 1.81 A, the S-N and S-0 lengths being 1.61 and 1.46 Arespectively. tiTwo structures of trinitromethane salts have been completed.365 Theconformation of the three nitro-groups in Rb+[C(NO,),]- and Cs+[C(NO,),]-are different, depending upon the nature of the cation; the G N bonds rangefrom 140-1*508. Tetra-acetylethane exists in the dienolic form in thecrystal with exact C, symmetry and approximate D2d symmetry in whichtwo substantially planar halves are twisted to 90" with respect to oneanother; it is of interest that each half probably contains a symmetricaland very short hydrogen bond (2.42 A).366 The positions of all the atoms,including hydrogen, have been determined for 1 -phenyl-2- (2-pyridy1)ethane-1,2-di0ne.~~7 The molecular configuration is similar to that of 2,2'-pyridyl-1,2-di-(2-pyridil)ethane-l,2-dione. The molecule consists of two planarparts, one of which contains a pyridine ring, a carbonyl group and itEladjacent carbon atom, and the other contains a planar phenyl group, acarbonyl group and its nearest carbon atom; the angle between these twoplanes is 88".A very careful structural analysis has been completed of cis-1,2,3-tri-cyanocyclopropane.36* The ring carbon-carbon bond length is 1.518 A, theexocyclic C-C bond length 1.449 A with the CiN value 1.144 8.A detailedanalysis of the electron distribution shows that the residual bonding electrondistribution is in good agreement with Coulson and Moffitt's predictions.In 7,7-dicyano-2,5-dimethylnorcaradiene, the C, ring is inclined at 73" tothe c6 ring; the c3 c-c bond lengths range from 1-50-1.56 A.Again the electron density in the C, ring is indicative of the value of thebent bond description.369 The NN-dimethylisopropylidenimium ion isplanar with a CiN+ bond length of 1.302 A and a C-CH, (OF N-CH,) distancesas F.P. Boer, J . Amer. Chem. Soc., 1966, 88, 1572.3'' L. G. Vorontsova, Zhur. strukt. Khim., 1966, 7 , 280.s8' J. P. Schaefer and P. J. Wheatley, J . Chm. Sm. (A), 1966, 528.8'7 T. Ashida, S. Hirokawa, and Y. Okaya, Acta C~yst., 1966, 21, 600.a* A. Hartman and F. L. Hirshfeld, Acta Cryst., 1966, ZB, 80.a'* C. J.Fritchie, jm., Acta Cryst., 1966, 20, 27.N. V. Grigor'eva, N. V. Margolis, I. N. Shokhor, V. V. Mel"nikova, and I. V.Tselinskii, Z h r . strukb. Khim., 1966, 7 , 278GIERLOCH AND MASON 741of 1.513 A. The H,C-N-CH, angle is 125.4" and the H,C-G-N angle 117.3'.Self-comistent-field calculations have been carried out in an attempt toaseign bond orders. 370 trans- 1,2 -Dibromo - 1,2 , - dimethoxy carbonylcy clo -butane possesses an approximate two-fold axis while the cis-molecule iscompletely symmetric.871 In the cis-isomer, the cyclobutane is puckeredwith a dihedral angle of approximately 150". The stereochemistry of acyclobutanone derivative has also been determined.37 *A model of syndiotatic polyacrylonitrile is afforded by an analysis ofthe racermic modification of 2,4-di~yanopentane.~~~ The five pentane carbonatoms form a planar zig-zag chain with the carbon-carbon bond lengthsbeing close to those normally found in molecules of this kind.The pentanechain in the DL-form of pentane-ZY4-diol &acetate is slightly twisted, thetwo acetate groups being planar but not co-planar with themselves.37*Several studies of the conformation of cyclohexane have been made, Acrystal structure determination of cyclohexane- 1,4-dioxime has been com-pleted at both room and low temperature and shows 375 that the molecularconformation may be described in terms of a twisted boat form with an anglebetween the two G O bonds of 154". This form of the ring has also beenobserved in two addition compounds of the dione-in the (1 : 1) additioncompound with di-iodo-acetylene and the (1 : 1) compound formed withmercuric chloride.In the dioxime the carbon skeleton of the moleculecorresponds to that of a twisted boat, the angle between the two CN bondsis 26", somewhat smaller than the corresponding angle between the two CObonds of the dione. In both trans- and cis-4-aminoethylcyclohexane-l-carboxylic acid hydrohalides, the molecules are found to exist in the chairform with an equatorial aminoethyl g r o ~ p . ~ 7 ~ In the trans form, the car-boxyl group is equatorial and the plane of the carboxyl group is roughlyperpendicular to the mean plane of the cyclohexane ring. In the cis form,the carboxyl group is axial and the orientation of the carboxyl plane is suchthat one of the carboxyl oxygen atoms is almost eclipsed by a carbon atomof the cyclohexane ring.In the (1 : 1) addition compound of cyclohexane-1,4-dione-di-iodoacetyl-eneYs7' the dione molecules are in the twisted boat conformation, the sameas in the dione itself and in the mercuric chloride addition compound.Thebonds linking the oxygen atoms to iodine atoms are weaker than the bondsbetween oxygen and mercury. In the iodine complex of l-oxa-4-selena-cyclohe~ane,~~~ the six-membered ring is in the chair conformation and theiodine molecule bonded to selenium in the axial position. The Se-I bonddistance of 2-76 is the shortest of its kind observed so far and the 1-1 dis-tance of 2.96A unusually long. Selenium forms a weaker bond with aw0 L.M. Trefonas, R. L. Flurry, jun., R. Majeste, E. A. Meyers, and R. F. Copeland,J . Amer. Chem. SOC., 1966, 88, 2145.871 I. L. Karle, J. Karle, and K. Britts, J. Amer. Chem. SOC., 1966, 88, 2918.a7a C. Riche, Compt. rend., 1966, 262, C , 272.373 L. E. Alexander, R. Engmann, and €3. G. Clark, J . Phys. Chem., 1966, 70, 252.s74 K. Tichy, Acta Cryst., 1966, 20, 865.376 P. Groth, Acta Chem. Scand., 1966, 20, 579.87g S. Kadoya, F. Hanazaki, and T. Iitaka, Acta Cryst., 1966, 21, 38.577 P. Groth and 0. Hassel, A& Chew. Scand., 1965, 19, 1733.878 H. Maddox and J. D. McCullough, Inorg. Chem., 1966,5, 522742 CRYSTALLOGBAPHYsecond iodine molecule but the oxygen atom is not involved in bondingoutside its own ring. In the complex, lithium chloride-1,4-dioxan, the1,kdioxan has the chair conformation and its dimensions are very similarto those found in other studies.The Li+ is bonded to two chlorines and twoseparate oxygen^.^^^ The 1,3-dithian ring in 2-pheny1-ly3-dithian has a,somewhat flattened chair conformation with the phenyl group in theequatorial position and has an orientation approximately perpendiculw tothe mean plane of the dithian ring.38* In truns-2,5-dibromo-l,4-dithian thethian ring again has a chair conformation with the bromine atoms in axialpositions. The only unusual features of this structural analysis are thevalues found for the C-G-S bond angle~.~SlThe cage portion of 4- (1,5-diazabicyclo[3,2,l]oct-8-yl}pyridine consistsof puckered five-, six- and seven-membered rings. The six-membered ringis in a chair conformation and the seven-membered ring in the boat con-f0rmation.~8~ Bond lengths in the pyridine ring resemble those in thequinoid type structure.Analysis of 6,6-dibromo-2,3 ;4,5-dimethano-2,4-dinitrocyclohexanone provides a determination of the posit'ions of the twocyclopropyl rings relative to the carboiiyl group.383 An X-ray analysis ofdextrorotatory 4- bromo- 6,l O-dirnethylbicyclo[5,3,0]decan-3-one gives thestructure shown in (21), the bromine atom being eq~atoria1.38~ The con-formation of the ring in cyclo-octane-l,2-trans-dicarboxylic acid is of a boat-chair form and not the stretched crown or ~addle.38~ In perchloro-(3,4,7,8-tetramethy1enetricyc1o[4,2,0,0 2, octane], the conformation of the threefour-membered rings as a whole is such that the molecule is chair-lil~e.~*~The perimeter of 1,6-methanocyclodecapentaene-2-carhoxylic acid is non-planar, t,he carbon-carbon bond lengths ranging from 1.38-1.42 A; themethylene bridge C-C bond length is 1-477 A and the C-C-C bond angle is99.6°.387 The whole geometry may be discussed in terms of intramolecularstrain energy.The geometry of a 14-membered ring has been determinedby the structural analysis of 1 $-diazo- 1,8-dihydroxycyclotradecane. Allbonds in the molecule correspond to single bond values and the angles areapproximately tetrahedral.388 The quasi-racemate from ( + )-m-methoxy-s70 F. Durant, Y. Gobillon, P. Piret, and M. Van Meerscho, Bull. SOC. china. belgca,1966, 75, 62.3*0 H.T. Kalff and C. Romers, Acta Cryst., 1966, 20, 490.a81 H. T. Kalff and C. Romers, Rec. Trav. chim., 1966, 85, 198.s82 I. L. ICarle and K. Britts, Acta Cryst., 1966, 21, 532.C. H. Stam and H. Evers, Rec. Trav. chim., 1965, 84, 1406.384 H. Sato, H. Minato, M. Shiro, and H. Koyama, Chem. Comm., 1966, 363.J. D. Dunitz and A. Mugnoli, Chern. Comm., 1966, 166.886 A. Furusaki, Y. Tomiie, and I. Nitta, Tetrahedron Letters, 1966, 493.M. Dobler and J. D. Dunitz, Helv. Chim. Acta, 1965, 38, 1429.C. J. Brown, J . Chem. SOC. (C), 1966, 1108GERLOCH AND MASON 743phenoxypropionic acid and (- )-m-bromophenoxypropionic acid shows theusual arrangement found in carboxylic acids, hydrogen bonding dimerisingthe molecules and the (+)- and (-)-molecules arranging themselves aroundthe pseudo-centre of symmetry.389The piperazine ring in 1 ,P-piperazine-yy-dibut~ic acid has the chairconformation and the structure is held together by 0-He-N hydrogen bondsof length 2.60k390 The glycolate ion in anhydrous lithium glycolate isnot planar, both atoms of the hydroxyl group being significantly displacedfrom the plane defined by the carboxyl group and the oc-carbon atom.Theglycolate ions are chelated to lithium ions and are linked by chains of trigonal-pyramidally co-ordinated lithium ions.391 Methylmalonic acid forms dimersin the crystal related, however, in this case by a, two-fold axis rather thanthe centre of symmetry which one usually finds in carboxylic acids. The0-H-0 bond length is quite short a t 2.645A.392 Two separate crystalstructure determinations of fumaric acid have been made.a-Bumaric acidcrystallises in a complex unit cell with two crystallographically non-equiva-lent molecules in the unit cell; there are parallel hydrogen-bonded chainswhich form sheets. The mean bond lengths in a-fumaric acid are : G-C, 1.465;C=C, 1-348; G-0, 1493; C=O, 1.224 and O-H*-O, 2.684A.3B3 @-Pumaricacid has a much simpler unit cell with hydrogen-bond lengths of 2.67;C=C, 1*315&0.007; G C , 1.450; G O , 19228, and G O , 1-289 A refine-ment of the structure of D-tartariC acid has been made by both X-ray andneutron diffraction methods. The neutron diffraction data confirms thehydrogen-bonding scheme deduced from the X-ray data. The molecule ismade up of two C*R,OH*CO,H parts, each part consisting of a planar car-boxyl group and a tetrahedral asymmetric carbon atom.There is a slightdifference in the overall shape between these two parts, the angle betweenthe planes of the carboxyl groups in these two moities being 54.6".39j Bur-ther refinement has also been carried out on hexamethylenediammoniumadipate and shows that the carboxyl group is twisted out of the plane ofthe carbon atom in the adipate ion by 70". N-H-0 hydrogen bonds inthe crystal link molecules together with a length of 2077A.396Rydrogen atoms have now been located in an analysis of pimelic acid.397It is interesting to note that the hydrogen-bond lengths in adipic, pimelic,and suberic acids are now given as 2.64, 2-68, and 2.65 A respectively.Thepositions of hydrogens have also been determined in sebacic acid, thehydrogen-bond length being 2.64 A.sgS In D L - ~ - bromo-octadeconoic acid,the chain is bent to accommodate the bromine atom.399 In dodecanedioicacid, the analysis is carefully discussed with particular reference to the effects8s I. L. Karle and J. Karle, J . Amer. Chem. doc., 1966, 88, 24.sso R. Potter, Acta Cryst., 1966, 20, 54.ssl E. J. Gave and 31. R. Taylor, Acta Cryst., 1966, 21, 418.D- J. Haas and S . A. Brenner, Actu Cryst., 1966, 20, 709.C. J. Brown, Acta Cryst., 1966, 21, 1.A. L. Bednowitz and B. Post, Acta Cryst., 1966, 21, 566.3s6 U. Okaya, N. R. Stemple, and M. I. Kay, Acta Crtpt., 1966, 20, 237.3s6 C. J . Brown, Acta Cryst., 1966, 20, 185.3s7 J.Housty and M. Hospital, Acta Cryst., 1966, 21, 29.8s8 J. Housty and M. Hospital, Actu Cryst., 1966, 20, 326.S. Abrahamson, and M. 31. Harding, Acta C~yst., 1966, 20, 377744 CRY STALL0 GRAPHYof hydrogen atom positions on the parameters of the carbon atoms, thelength of the C-C bonds, distances and angles in the carboxylic groups.mThe S-S bond length in 1,2-dithiolan-4-carboxylic acid is 2.096 8, thedihedral angle C-S-S/S-S-C is 27.5" and the GS bond length 1+3O5k4OlIn the crystal, the uric acid molecule has the triketo-form, the molecule beingstrictly planar; there is a variety of N-H-*O and 0-HI-0 hydrogen-bondlengths. A comparison of bond lengths and bond angles with those of otherpurines and pyrimidines shows only small de~iations.~*2 The structures ofadipa~nide,~~~ ~uberamide,~~~ and glutaramide 40s have all been completed.In adipamide, 0-€I-N hydrogen bonds of 2.93 and 2-94A hold the rnole-cules together, all other bond lengths being normal.In suberamide, theN-H***O hydrogen bond lengths are'2.91 and 2*97A, the C-C, GO, andGH bond lengths and angles being consistent with those found in otheraliphatic compounds. In glutarimide, the intramolecular bond lengths areagain of the usual order and N-H-*O hydrogen bonds of 2.97 and 2*94Bhold the molecule together. All the atoms of hydroxyurea 406 except thehydroxyl-hydrogens are coplanar, the molecules being connected by a three-dimensional system of hydrogen bonds of the types 0-H-0 and NH-0.The intramolecular bond lengths are : C-N, 1.33 ; GO, 1.27, and O-N,1-41 A.The molecular structure of methylpinacol phosphate 407 is very similarto that of methylethylene phosphate.The most significant difference liesin the position of the methyl ester group. In methylpinacol phosphatethe methyl group lies over the phosphoryl oxygen and it is suggested thatthe position of the methyl ester group can be discussed in terms of n-bonding.In disodium ,%glycerolphosphate pentahydrate, each of the phosphate-oxygen atoms is either hydrogen bonded or co-ordinated to sodium ionswith the Na-0 distances ranging from 2.27-2-59 A.eo8 The ring of methyl1 -thio-/l-mxylopyranoside adopts the chair conformation, generally withnormal bond lengths and angles although there appears to be some shorten-ing of the anomeric carbon-sulphur bond and one ring angle is significantlylarger than tetrahedral.The ring oxygen atom does not participate in thehydrogen-bonding system which is confined to the hydroxyl Theconfiguration of the dioxolan carbon atom of 1,2-O-aminoisopropylidene-cc-D-glucopyranose hydroiodide has been determined."O The five-memberedring is slightly non-planar having an envelope conformation. The amino-methyl group is in the equatorial position and the absolute configuration isestablished since this compound is derived from D-glucose. The pyranosering has a flattened chair conformation. The configuration given by Haworth400 J. Housty and M. Hospital, Acta Cryst., 1966, 21, 553.401 0. FOSS, A. Hordvik, and J.Eletten, Acta Chem. Scand., 1966, 20, 1169.402 H. Ringertz, Acta Cryst., 1966, 20, 397.408 M. Hospital and J. Housty, Acta Cryst., 1966, 20, 626.404 M. Hospital and J. Housty, Acta Cryst., 1966, 20, 368.405 M. Hospital and J. Housty, Acta Cryat., 1966, 21, 413.406 I. K. Larsen and B. Jerslov, Acta Chem. Scand., 1966, 20, 983.40' M. G. Newton, J. R. Cox, jun., and J. A. Bertrand, J. Amer. Chem. SOC., 1966,408 Mazhar-ul-Haque and C. N. Caughlan, Chem. Comm., 1966,214.40D A. McL. Mathieson and B. J. Poppleton, Acta Cryst., 1966, 21, 72.41O J. Trotter, and J. K. Fawcett, Acta Cryst., 1966, 21, 366.88, 1503GERLOCH AND MASON 745of methyl /?-xyloside has been confirmed, the pyranose ring being in thestrainless trans form.411 Glyoxime has the oxime form with anti-$-trans-(C&,) symmetry.412 Molecules are linked by O-H*-N hydrogen bonds of2.81 A.Each sodium atom in NaBr,2MeCO*NH2 is octahedrally co-ordin-ated, the structure consisting of infinite chains of octahedra with oneface in common. The crystal and molecular structures of cis- and truns-octa-2,4,6-triene-I ,4;5,8-diolide and of the tram-2,7-dimethyl derivativehave been reported and compared in some detail.414 The basic structure inMeCN,2HCl is that of the imino hydrochloride,K>:N<;]+ c1-and the chloride ion is involved as an acceptor in two hydrogen bonds.415X-Ray data confirms the structure of the cycloadducts from 3- and 4-bromo-N-methoxycarbonylazepine and tetracyanoethylene as 8,8,9,9-tetracyano-Z-methoxycarbonyl-2-aza bic y clo [ 3,2,2]nona-3,6-dienes, the crystals cont ainnga mixture of isomers.416Lipids.-In the L-1 -monoglyceride of 11 -bromoundecanoic acid, themolecules are arranged " head-to-head " in layers with parallel hydrocarbonchains.Only :the hydroxyl groups participate in the hydrogen-bondA refinement of the structure of ,/3-tricaprin shows that themolecules are packed as modified tuning forks " in which two chains withtwo glyceryl-carbon atoms and two ester-oxygen atoms form a nearlyatraight chain while the third chain branches off by way of the third glyceryl-carbon atom and an ester-oxygen atom.418 L-a-Glycerylphosphorylcholine,the basic unit of the lecithins, adopts two conformations in the crystal,namely the gauche-trum and the gauche-gau~he.~~~ The gauche conforma-tion is adopted about the bond of the two ethyl-carbon atoms of the nitrogenbaae and this is the same as is observed in 2-aminoethanol phosphate.Aromatic Molecules.-The detailed structure of the flrst two n-electronsystem has been determined from the analysis of s- triphenylcyclopropeniumperchlorate. The triphenylcyclopropenium perchlorate ion is non-planar,the phenyl groups being twisted in a propeller-like arrangement and makingrespective angles of 8", 12", and 21" with respect to the C3 plane.Theaverage C-C bond length in the C3 ring is 1.73, the average exocyclic bondlength being 1-44 8 . 4 2 0 In rubidium hydrogen croconate and ammoniumhydrogen croconate, hydrogen bond formation leads to ring chains in thecrystal and the anion does not have C, symmetry.The O-H--O bond lengths411 C. J. Brow, (in part) S i r G. Cox and F. J. Llewellyn, J . Chem. SOC. (A), 1966,922; C. J. Brown, ibid., p. 927.M. Callmi, G. Ferraris, and D. Viterbo, Acta Cryat., 1966, 20, 73.P. Pht, L. Rodrique, Y. Gobillon, and M. Van Meersche, Acta Cryst., 1966,20,482.414 A. CoIombo and 0. Allegra, Acta Cryst., 1966, 21, 124.&lS S. W. Peterson and J. M. Williams, J . Amer. Chem. SOC., 1966, 88, 2866.'18 L. H. Jensen and A. J. Mabis, Acta Cry&., 1966,21, 770.41a S. Abrahameson and I. Pascher, Acta Cryst., 1966, 21, 79.4a0 M. Sundaralingam and L. H. Jemen, J . Amer. Chern. SOC., 1966, 88, 198.I. C. Paul, J. E. Baldwin, and R. A. Smith, J. Amer. Chm. SOC., 1966,88, 3653.K.Lamson, Ada Cryst., 1966, !20, 267746 CRYSTALLOGRAPHYare 2-50 and 2-46 A and the double bond is not completely delocalised.4~1A refinement of the structure of coronene has been completed and some dis-crepancies between observed and calculated bond lengths discussed ; themolecule does not appear to be strictly planar.422The complete determination of the unusual aromatic molecule, 1,8-bis-dehydro[l4]annulene has been reported in detail including the positions ofthe hydrogen atoms. The agreement between observed and theoreticallypredicted C-C bond lengths is better than 0.01 A. Distortions of carbonbond angles from strict trigonal and digonal symmetry are attributed tointramolecular steric interactions between hydrogen atoms, or carbon, orother hydrogen atoms.423 Each anthracene ring in p-dianthracene is bentby a total of 46" about $he p-positions, the joining C-C bond being 1.61 A.424The structure of the photoisomer is very similar in that again the rings areinclined at 46 O.Intramolecular overcrowding between chlorine and hydrogenatoms in 9,9,10,lO-tetrachloro-9,1O-dihydroanthracene forces the carbonframework of both molecules into an essentially planar configuration andhence into a strained conformation with the central cyclohexa- 1,4-dienerings.425 The detailed G-C bond lengths of biphenylene show that it mustbe considered as a cyclobutane derivative. Bond lengths between thecarbons joining the six-membered rings are 1.514 A while those in the six-membered rings vary from 1.426-1-372 An interesting analysis isrepresented by the molecule of aluminium chloride-benzoyl chloride com-plex.427 The adduct is composed of an AICl, group co-ordinated with theoxygen of the benzoyl chloride group.The benzoyl chloride group is co-planar with the aluminium atom and one chlorine atom bound to it. Twoother chlorine atoms, co-ordinated to the aluminium, are located above andbelow the molecular plane. The aluminium is essentially tetrahedral. Themolecule of benzofuroxan is planar with the six nitroso-substituents formingthree furoxan rings.428 An example of the power of X-ray analysis isrepresented by the investigation of the reaction of benztrifurazan withtriphenylphosphine. One of the products is an unusual difurazan (22)."9NHN (2.2)Oy \OHIn 2,3,4,6-tetranitroaniIine there are significant differences from normalbenzene bond lengths in the six-membered ring; those at the carbon of the(I1 N.C. Baenziger and D. G. Williams, J. Amer. Chm. SOC., 1966, 88, 689.4ar M . Ehrenberg, Acta Cwst., 1966, 20, 177.Isti W. F. Yannoni and J. Silverman, Acta Cryst., 1966, 21, 390.426 J. IC. Fawcett, and J. Trotter, Acta Cryst., 1966, 20, 87.427 S . E. Rasmussen and N. C. Broch, Acta Chcm. Scand., 1966, 20, 1361.J. K. Fawcett and J. Trotter, Proc. Roy. Soc., 1966, A , 259, 366.N. A. Bailey and R. Mason, Proc. Roy. Xoc., 1966, A , 290, 94.H. H. Cady, A. C. Larson, and D. T. Cromer, Acta Cryst., 1966, 20, 336.A. S. Bailey, T. S . Cameron, J. M. Evans, and C. K.Prout, Chem. C m . , 1966,604QERLOCH AND MASON 743amine-group average 1-43, the remainder 1.37 A. The molecule as a wholeis not planar.430 The ring bond lengths in p-chloroaniline have the usualvalues ; the C-Cl length is 1.75, C-N, 1-40 8, and the molecule is essentiallyplanar.431--433 A comparison of the structure of p-nitrobenzoic acid withp-nitroaniline and p-nitrophenol has been made and the variations inter-preted as being due to minor contributions from quinoid valence-bondstructures.434 o-Fluorobenzoic acid forms centrosymmetrical dimers throughhydrogen bonds between adjacent carboxyl groups. The molecule is over-crowded, the carboxyl group being rotated about 20" out of the plane of thearomatic ring.435 In acetyl-2-pyridine chlorohydrate, each chlorine atom islinked to one nitrogen atom by a hydrogen bond of length 3*03& TheC-N length is 1-34 A and the G-C bond lengths range from 1.39-1-40The molecules of N-methylpyridine-2-aldoxime halides are in the syn-form,the planar molecules forming a layered structure.The bond lengths andbond angles in the pyridine ring are quite normal, but the C-N bond in theosime moiety shows a less pronounced double-bond character than is usuallyfound in oximes, which may be partly due to the close approach of an iodineion.P37 In picolinamide, the pyridine rings have mean G-C bond lengths of1-33, and C-N of 1-34 A while in the amide, the lengths are: C-C 1.52,G O 1-24, and C-N 1-33 8. The pyridine ring is planar, the angle betweenthe plane of the pyridine and that of the amide being 19°.43g In l-methyl-6-[5- (1 -methyl- 1H- 1 -pyridinyl)]- 1 -azoniaindane iodide, the 1,5-disubsfituted-1H-l-pyridine half of the molecule is iso-n-electronic with azulene.Bondlengths and the overall geometry are in agreement with aromatic character.439The molecule of 8,8'-dibromo-2,2'-methylenediquinoline is non-conjugated,the central carbon atom being clearly a, CH, group connected with G-Cbonds of 1.51 A to the quinoline ring. The C-CH,-C valency angle is 112",the dihedral angle between the two planar quinoline rings is 77°.440 Inm-dinitrobenzene, each nitro-group is rotated out of the aromatic plane byabout 13" and the directions of the rotations are such that the molecularsymmetry is C,.441 AU C-C bond lengths are, within experimental error,identical with that of benzene itself.The anisylic part of p-methoxyindo-phenol-N-oxide has the expected bond lengths and bond angles. The twosix-membered rings are oriented a t an angle of 64* with respect to oneanother.442 The benzoquinone-N-oxide moiety of the molecule in a-5-(2'-ch1oroethoxy)-o-quinone 2-oxime has bond lengths similar to those inbenzoquinone. In catechol, the mean C-C bond length is 1-3858, againC.480 C. Dickinson, J. M. Stewart, and J. R. Holden, Acta Cryst., 1966, 21, 663.431 J. H. Palm, Acta Cryst., 1966, 21, 473.48a J. Trotter, S. H. Whitlow, and T. Zobel, J . Chem. SOC. (A), 1966, 353.438 V. R. Sarma, Indian J. Pure Appl. Phys., 1966, 4, 226.434 T. D. Sakore and L.M. Pant, Acta Cryst., 1966, 21, 715.435 J. I(rauase and H. Dunken, Acta Cryst., 1966, 20, 67.4s6 A. Laurent, Acta Cryst., 1966, 21, 710.457 C. Darlstrorn, Acta Chem. Scand., 1966, 20, 1240.T. Takano, Y. Sasada, and M. Kakudo, Acta Cryst., 1966, 21, 514.48n H. L. Ammon and L. H. Jensen, J. Amer. Chem. Soc., 1966,88, 681.440 J. van Thuijl and C. Romers, Acta Cryst., 1966, 20, 899.441 J. Trotter and C. S. Williamson, Acta Cryst., 1966, 21, 285.44a C. Romers and B. Hesper, Actcz Cryst., 1966,20,162-169; J. W. L. van Oijen andRomers, {bid., p. 169748 CBYSTALLO GRAPEYidentical, within experimental error, with that of benzene, and the C-0 bondlength is 1.372 Hydrogen bonds of 2.80 A connect molecules togetherin the crystal. 2,3-Dichloro-ly4-benzoquinone has a geometry quite similarto that of chloroanil but a different bonding scheme is envisaged for2,5-dibromo- 1,4-benzoquinone, 2-bromo-5-chloro- 1,4-benzoquinone and 2,5-di~hloro-l,4-benzoquinone.~~~ The hydrate of 2-methyl-3-amino-1,4-naph-thaquinone, 2C,,02NH,,+H,0, forms very nearly planar hydrogen-bondedtetramers, centred at the origin and connected to others by two hydrogenbonds, NH***O and 0-**HN.445 3-Amino-2-bromo-l,4-naphthaquinone existsas dimers with hydroxy-bonds linking the amino- and ketonic-groups andthe amino-groups and bromine atoms.446 The structure of anthraquinonshas been determined a t five temperatures and is of particular interest inrelation to the thermal expansion coefficients of the crystal and an analysisof the molecular vibrations in terms of rigid-body vibrations and independentatomic vibrations.447 Exhaustive X-ray studies have also been made ofthe single-crystal chemical reaction of the photo-oxide of anthracene toanthraquinone and anthrone.The chemical reaction proceeds by inter-mediate stages of disorder, decomposition, and recrystallisation which havebeen followed in some detail. The geometrical mechanism of the reactionsseems to be the same whether it is caused by X-irradiation or thermally,The nature of the final product and some probable breakdown in intermedi-ates and radicals was determined by mass spectrometry.44g In 1,2,3-tri-bromo-6-(o-methoxyphenyl)fulvene, the mean bond length in the fulvalenering is 1-31 A. Both the benzene and fulvalene rings are planar with theplane of the benzene ring oriented at an angle of 39" with respect to theplane of the fulvene ring; the methyl group in the methoxy-group deviatesfrom the plane of the benzene.449 The mean G-C bond length in the benzenering of 1,2,3,4-tetrachlorobenzo[g]sesquifulvalene is 1.43 A.The five-mem-bered and the seven-membered rings are twisted with respect to one anotherby an angle of approximately 31 O around the connecting bond.46* The planeof the seven-membered ring makes an angle of only 5" to that of the six-membered ring. The analysis of p-azotoluene resulted in the discovery of atype of disorder in which the step of the azo-group is random in either of twodirections a t equivalent lattice points. This disorder accounts for theabnormality observed in the bond length~.~51 Azobenzene is ako disorderedin a similar way.452 Trans-pp'-Dibromoazobenzene has an N-N bond lengthof 1.276, C-N, 1.428, G-C, 1.390, and GBr, 1.891 A.453As in previous years, several structure determinations have been con-44a C .J. Brown, Acta Cryst., 1966, 21, 170.444 B. Rees, R. Haser, and R. Weiss, Bull. SOC. chim. France, 1966,2668,2666,2671.445 J. Gaulthier and C. Hauw, Acta Cryst., 1966, 21, 694.446 J. Gaulthier and C. Hauw, Acta Cryst., 1966, 20, 620.447 K. Lonsdale, H. J. Milledge, and K. El. Sayed, Acta Cry&., 1966, 20, 1.448 K. Lonsdale, E. Nave, and J. F. Stephens, Phil. Tram., S ~ T . A , 1966, 261, 1.44B Y. Kato, Y. Sasads, and M. Kakudo, Bull. Chem.SOC. Japan, 1965, 38, 1761.460 Y. Nishi, Y. Sasada, T. Aahida, and M. Kakudo, Bull. Chern. Soc. Japan, 1966,461 C . J. Brown, Acta Cryst., 1966, 21, 153.4 6 ~ C. J. Brown, Ada CTYS~., 1966, 21, 146.39, 818.A. G. Amit and H. Hope, Ada Chern. Scand., 1966, 20, 835GERLOCH AND MASON 749cerned with molecular complexes. In the structure of the 2,4,6-tri(&methyl-amino)-l,3,5-triazine-s-trinitrobenzene complex, the component moleculesare stacked alternately in infinite columns, the mean perpendicular separationof the molecules baing 3.36 8. Each component molecule of the complex isplanar to within experimental 8 1 . ~ 0 1 . ~ ~ ~ In the pyrene-tetracyanoethylenecomplex, the molecules are again alternately stacked but the centre of theTCNE molecule is not directly above that of neighbouring pyrene molecules.The mean separation of the molecular planes is 3-32 Both moleculesin the acepleiadylene-l,3,5-trinitrobenzene complex are significantly non-planar, the interplanar spacing being 3.26 A.456 N-Methylphenaziniumtetracyanoquinodimethanide is the best known organic electrical conductorand the tetracyanoquinodimethan anion radicals form a charge-resonancebonded column with interplanar spacing of only 3.26 A.457 The van derWaals spacing in the similar column of phenazinium cations is 3.36 A.Allinterplanar separations within the tetracyanoquinodimethanide columnsare short charge-resonance contacts of 3.22 and 3.26 A. In the structure ofczsium tetracyanoquinodimethanide,458 the steric relationship of two-thirds of the vicinal pairs is strikingly similar to that in N-methylphena-ziniumtetracyanoquinodimethanide.The structure of the iodide of 4-4'-bis(dimethy1amino)diphenylamine has also been determined.459 The cationradical is roughly planar and interatomic distances indicate extensive con-j ugation. The sodium ions in sodium naphthionate tetrahydrate are approx-imately octahedrally co-ordinated to six oxygen atoms, the mean Na-0distance being 2.42 A. In the anion, the distances are: S-0,1.45; S-C, 1.77;and C-N, 1.41 A. In the aromatic ring four G-C distances have mean of1.37 and seven of 1*42& which are very similar to the values in naph-thalene.460 In 2-chlorotropone, the seven-membered ring is planar, theoxygen atom being roughly displaced out of the ~ l a n e .~ ~ l The molecule ofphenoxothionine is folded about the line joining heterocyclic atoms, throughan angle of 138".462 This is very similar to the dihedral angle found in/3-thianthrene dioxide where it is 133°.463 The structural analysis 464 ofdibenzoylmethane is of particular significance since the crystal structurehas been determined by considerations of molecular packing. Dibenzoyl-methane is non-planar, the planes of the two phenyl groups making anglesof -4" and +17" with respect to the enol ring. A short hydrogen bond of2.47 appears to be non-linear, asymmetric, and non-statistical. Both1,6-di-p- and 1,6-di-o-chlorophenyl-3,4-dimethylhexatriene are approximatelyplanar with G C l distances of 1.74 and 1.73A.The effect of the methyl454 R. M. Williams and S. C. Wa,llwork, Acta Cryst., 1966, 21, 406.455 H. Kuroda, I. Ikemoto, and H. Akamatu, Bull. Chem. SOC. Japan, 1966,39, 547.456 A. W. Hanson, Acta Cryst., 1966, 21, 97.457 C. J. Fritchie, jun., Actn Cryst., 1966, 20, 892.458 C. J. Fritchie, jun., and P. Arthur, jun., Acta Cryst., 1966, 21, 139.45s K. Toman and D. Ocenaskova, Acta Cryst., 1966, 20, 514.460 C. J. Brown and D. E. C. Corbridge, Acta Cryst., 1966, 21, 485.46a S. Hosoya, Acta Cryst., 1966, 20, 429.464 D. E. Williams, Acta Cryst., 1966, 21, 340.E. J. Forbes, M. J. Gregory, T. A. Hamor, and D. J. Watkin, Chem. C m . , 1966,S . Hosoya, Acta Cryst., 1966, 21, 21.114750 CRY STALL0 GRAPH Ygroups on the bond angles in the conjugated chain is to decrease the angleopposite the C-CH, bond in agreement with previous results on carotenoidc0mpounds.~6~ Intermolecular G-H***O hydrogen bonds of length 3.21 Alink ethynyl groups to neighbouring carbonyl oxygen atoms in the crystalstructure of o-chlorobenzoylacetylene.466 The molecule is significantly non-planar, the plane of the exocyclic ethynyl-carbonyl group making an angleof 7” with that of the benzene ring.A dehydropyrolidone, p-bromophenyl-aza- l$-phenyl- 2- benzylidene-4,5- cy clopentene -3 -one, is planar except forthe benzene rings which are inclined at an angle of 50’ to the mean molecularplane. 467Heterocyclic Molecules.-Rhodan hydrate is approximately planar 468with bond lengths: C-N 1.336 and 1.408, S-C 1-77, C-0 1.22, and S-S 2-06 A.The five-membered ring of imidazole is strictly planar, all the bond lengthsindicate extensive delocalisation (average C-N bond length 1.36 and C-C1-36A) and there are very short NR-N hydrogen bonds ofPyridoxine is planar with the exception of the oxygen atom from the CH20Hgroup.470 3,3’-Bi-2-isoxazolinyl consists of two five-membered isoxazolinerings with the bridging C-C bond of 1.42 A and is essentially planar.471 Astructure determination has been completed of a C,N-disubstituted oxaziri-dine (23) produced by the ultraviolet radiation of anti-4-brom0-2~6-dimethyl-0 - NMeCH \ ’N-methylbenzaldoxime ; of particular interest is the presence of a three-membered (N-GO) ring in the m0lecule.~72 The reaction of ezo-3-phenyl-3,4,5-triazatricyclo[5,2,1 ,Q 2 9 61dec-4-ene and p - bromophenyl gives a veryunusual heterocycle (24).47s A detailed analysis of porphine 474 shows themolecule to be essentially planar and indeed a comparison of the crystalstructures of several porphyrins indicates that the porphine skeleton isprobable planar or nearly planar in the vapour phase, although markedruffling occurs in some crystals because of crystal-packing forces.The wide465 C. H. Stam and L. Riva di Sanseverino, Acta Cryst., 1966, 21, 132.‘ 1 3 ~ G. Ferguson and IC. 31. S. Islam, J. Chem. SOC. ( B ) , 1966, 693.468 A. Hordvilc, Acta Chem. Scand., 1966, 20, 754.46* S. Martinez-Camera, Acta Cryst., 1966, 20, 783.470 F. Hanic, Acta Cryst., 1966, 21, 332.471 A. L.Bednowitz, I. Fankuchen, Y. Okaya, and M. D. Soffer, Acta Cryst., 1966,*’* L. Brehm, K. G. Jensen, and B. Jerslev, Acta Chena. Scund., 1966, 20, 915.473 J. E. Baldwin, J. A. Kapecki, M. G. Newton, and I. C. Paul, Chem. Comm.,474 L. E. Webb and E. B. Fleischer, J . Chem. Phys., 1965, 45, 3100.0. Lefebre-Soubeyran, Bull. SOC. chim. France, 1966, 1242, 1249, 1266.20, 100.1966, 352GERLOCH AND MASON 751variation in molecular configuration found in different crystals emphasisesthe easy deformability of the molecule and this property may be importantin biological mechanisms. In 4- hydroxycoumarin monohydrate, the hydroxy-coumarin molecule does not appear to be strictly planar; hydrogen bonds:exist between water molecules and the 4-hydroxycoumarin molecules, oflength 2.59, 2.73, and 2-80 8 .4 7 5 In 2-chloro-1,3-dithia-2-stibacyclopentane,the five-membered ring is non-planar with the dihedral angle between thetwo halves of the molecule hinged about the disulphide line being 168°.4762H-Pyridaz-3-thione' is only slightly distorted with the sulphur atom lyhg0.03 A from the mean plane of the ring system; the planar molecules formdimers through S-H-N hydrogen The cyanine cation in bis-(N-ethyl-2-benzothiazole)phosphamethine perchlorate is symmetric andaccurately planar. The benzthiozones are in cis-positions, the planes beingtwisted at an angle of 6" in respect to one another. The intramolecular S-Sdistance is only 2-95 8, the G-P bond length indicating extensive delocalisa-tion.478 In 1,4-bis-(N-ethyl-2,3-dihydrobenzothiazol-2-ylidene)tetraz-2-en,the tetrazene chain is present in the truns-(N)-trans-tran-(N) form.479Steroids.-The molecular structure of 2or-bromo-5~-bromomethyl-5a-methyl-2~-oxo-l,3,2-dioxaphospharinane is best described as a distorted chairwith the bromomethyl groups in axial p~sition.~~O All three six-memberedrings of the steroid skeleton of 2~,3a-dichloro-5a-cholestabe are in the chairform, the five-membered ring having a half chair configuration.481 Theobserved bond angles within the cyclohexane rings are connected with theflattening of the perhydrophenanthrene skeleton.4-Bromo-S~,lOa-pregna-4,6-diene-3,20-dione has a bent shape with the distorted chair conformationof ring Androsterone shows considerable distortion, particularly ofthe angular methyl gro~ps.~*3Terpenes.-Monoterpenes. Two separate determinations of the struc-ture and absolute configuration of 3-bromocamphor have been made.484, 485A reference list of organic structures whose absolute codgurations havebeen determined by X-ray methods is also given.484 The lactone rings inanemonin are in the trans configuration.The cyclobutane ring is bent with adihedral angle of 152" and the C-C bond lengths in the cyclobutane ringhave normal single-bond values of approximately 1.54 g.486Sesquiterpenoids. Analysis of humulene bromohydrin revises the con-stitution to that shown in (25). The cyclobutane ring is trans-fused and hasthe same mode of fusion as that found in caryophyllene hydrochloride and476 J.Caulthier and C. Hauw, Acta Cryst., 1966, 20, 646.476 M. A. Bush, P. F. Lindley, and P. Woodward, Chem. Comm., 1966, 149.478 R. Allmann, Chem. Ber., 1966, 99, 1332.479 R. Allmann, Angew. Chem., 1966,78,147.480 T. A. Beineke, Chem. Comm., 1966, 860.481 H. J. Geise, C. Romers, and E. W. M. Rutten, Actu Cryst., 1966, 20, 249; H. J.r 8 a C. Romers, B. Hesper, E. van Heijkoop, and J. H. Gieee, Actu Cryst., 1966, 20,lS3 D. F. High and J. Kraut, Acta Cryst., 1966, 21, 88.486 M. G. Northolt and J. H. Palm, Rec. Trav. china., 1966, 85, 143.4 8 6 I. L. Karle and J. Karle, Acta Cryat., 1966, 20, 555.C. H. Carlisle and M. B. Hossain, Acta Cryst., 1966, 20, 249.Gese and C. Romers, ibid., p. 257.363.F. H. Allen and D. Rogers, Chem. Comm., 1966,837752 CRYSTALLOGRAPHYcarophyllene chlor~hydrin.~~~ The analysis of a humulene-silver nitrateadduct shows the structure to be that in (26) and agrees with predictionsfrom considerations of the probable biogenesis of humulene from farnesol.488In acorone, the cyclohexane ring has the chair conformation with an axialmethyl group.The structure may be different in solution and the cyclo-pentanone ring has an envelope rather than half-chair conformation.489The constitution and relative stereochemistry of bromomexicanine is shownin (27). Both five-membered rings are trans-fused to the seven-memberedrings, the two fusions being cis-syn-cis. The seven-membered ring is in theboat conf~rmation.~~ A new type of ring system is found in trichodermin 491which leads to the revision of the previously assumed structures of compoundssuch as verrucarol and trichotecin (28).The structure of hirsutic acid hasbeen determined 4g2 by X-ray analysis of the parabromophenacyl ester, allfive-membered rings having an envelope conformation (29). The chemicalformula of bromonoranisatinone, shown in (30), has been determined directlyby X-ray methods.493The molecular distortions in beyerol monoethylidene iodo-acetate are largely due to the fusion of the bridge system and to intramole-cular steric interactions. 494 The molecule of isoeremolactone consists ofthree six-membered rings bridged together in the boat conformation with itfive-membered ring attached to one of them. The side chain is confirmedDiterpenes.487 F.H. Allen and D. Rogers, Chem. Comrn., 1966, 582.488 A. T. McPhail and G. A. Sim, J . Chem. SOC. ( B ) , 1966, 112.ui0 C. E. McEachan, A. T. McPhail, and G. A. Sim, J . Chem. SOC. (C), 1966, 679.490 C. N. Caughlan, Mazhar-ul-Haquo, and M. T. Emerson, Chem. Comm., 1966, 161.491 S. Abrahamsson and B. Nilson, Acat Chem. Scad., 1966, 20, 1044.4Bs F. W. Comer and J. Trotter, J . C'hem. SOC. ( B ) , 1966, 11.493 N. Sekabe, Y. Hirata, A. Furusaki, Y. Tomiie, and I. Nitta, Tetruhedron L e t t e ~ ~ ,494 A. M. &Connell and E. N. Maslen, Acta Cryst., 1966, 21, 744.1965, 4795QERLOCH AND MASON 753O=as a y-lactone.495 The analysis of deacetylcascarillin acetal iodoacetate hasestablished 4 9 ~ the constitution and absolute stereochemistry of cascarillin,the diterpenoid bitter principle of cascarilla bark.The stereochemistry ofisocolumbin has been determined 497 by an X-ray study of l-p-iodophenyl-3-phenylpyrazoline adduct of isocolumbin and the structure confirmed as (31).The stereochemistry of the three boat-shaped six-membered rings and theortholactone systems has been examined in detail. The constitution andstereochemistry of the p-iodocenzoate of trio1 Q acetonide 498 is establishedtw (32). The structure and absolute configuration of enmeine has been deter-mined through the analysis of acetyl-bromoacetyldihydroenmein.499 Theabsolute stereochemistry of gibberellic acid has been determined 5oo via theBijvoet method and is shown in (33).O RTriterpenes. In 3-acetoxy-7,l l-dibromolanostane-8,9-epoxide, ring A hasthe normal chair formation, D is in a half-chair conformation and rings Band o are prevented from adopting the chair conformation by the epoxidebridge.601 Both the side chain and the C-9 21 methyl group are cc-oriented ineuphenyl iodoacetate; the side chain is not fully extended with respect to496 Yow-Lam Oh and E.N. Maslen, Tetrahedron Letters, 1966, 3291. '*' C. E. McEachan, A. T. McPhail, and G. A. Sim, J. Chern. SOC. (B), 1966,633.4p7 K. K. Cheung, D. Melville, K. H. Overton, J. M. Robertson, and 0. A. Sim,G. Ferguson, J. W. B. Fulke, and R. McCrindle, Chern. Cmm., 1966, 691.4gg M. Natsume and Y. Iitaka, Acta Cryst., 1966, 20, 197.6oo P. McCapra, A. T. McPhail, A. I. Scott, U. A. Sim, and D. W.Young, J . Chem.601 J. K. Fawcett and J. Trotter, J . Chem. SOC. ( B ) , 1966, 174.J . Chern. SOC. ( B ) , 1966, 853.SOC. (C), 1966, 1577754 CRYSTALLOGRAPHYthe rest of the molecule.502 A direct crystallographic determination of thestructure of davallol iodoacetate 503 confirms the absolute configuration ofdavallic acid proposed by Nakanishi and his colleagues. The chemicalstructure of fusidic acid proposed by Godtfredsen and Arrigoni has beenconfirmed by the analysis of fusidic acid methyl ester 3-p-bromoben~oate.~0*The tetranortriterpenoid swietenine has the conformation (34).605H H 0<O&%0'(3 9)-0 CO*CH:CH P h(37)Alkaloids.-The structure of phyllochrysine iodomethylate has beendetermined 506 and the structure is shown to be (35).The establishment ofthe structure of ochotensine and ochotensimine (36) is of very considerableimportance.jo7 9 liog The absolute configuration of luciduscile hydroiodidehas been established by the anomalous dispersion method. The molecule ismade up of four six-membered rings, three of which have the boat con-formation and one a chair conformation; the iodine atom lies between thetwo alcoholic hydroxyl groups of the same molecule, and a hydrogen-bonded chelate structure is suggested.509 An X-ray examination of thechloroplatinate of an alkaloid derived from Senecio kirkii shows the cationto have formula (C,,H,,NO,)+ which differs in the absence of a methylenegroup from that corresponding to the now known structure of ~enkirkine.~~~The stereochemistry of the indolizidinc skeleton of the solanidanes has beendetermined by an X-ray examination of demissidine hydroiodide.Thus allthe natural solanidane alkaloids demissidine, solanidine, leptinidine, rubi-jervine, isorubijervine, and veralobine are proved to possess the (22R:NS)-configuration, whereas the so-called 22-isosolanidanes have (ZZX:NS)-con-figuration. According to chemical transformations the absolute configura-C. H. Carlisle and M. F. C. Ladd, Acta Cryst., 1966, 21, 689.Yow-Lam Oh and E. N. Maslen, Acta Cryst., 1966, 20, 852.A. Cooper, Tetrahedron, 1966, 22, 1379.A. T. McPhail and G. A. Sim, J . Chem. SOC. ( B ) , 1966, 318.C. Pascard-Billy, Bull. SOC. c7h.n. France, 1966, 369.A. McLean, Mei-Sie Lin, A. C. Macdonald, and J.Trotter, Tetrahedron Letter4A. C. Macdonald and J. Trotter, J . Chem. SOC. ( B ) , 1966, 929A. Yoshino and P. Iitaka, Acta Cryst., 1966, 21, 67.m0 G. G. Dodson and D. Hall, A& Cryst., 1966,20,42.1966, 185GERLOCH AND MASON 765tions of the known stereoisomeric 22,26-iminocholestanes at (3-22 can alsobe given.611 The analysis of 2,5,9,10-tetra-0-acetyl-l4-bromotaxinol showsthe structure of taxanine to be (37) which differs from that given by earlierchemical studies in the configurations of three carbon atoms.512 Thestructure of the perloline cation C,,,Hl,N,03 has been determined by theX-ray analysis of the hydrated mercurichloride. The perloline chloride hasthe amide-like structure of uncha,rged 2-pyridi11e.61~ The molecule of sperm-ine tetrahydrochloride has an unusual conformation; inatead of beingzig-zag planar, two of the four bonds between carbon atoms and imino-nitrogen atoms are in gauche conformations.The G-C bond lengths are1-82 and C-N, 1.50A. The strongest interactions in the crystals occurbetween the N+H, and N+H, groups and the chloride ions.614 The conforma-tion of the chain in spermidme trihydrochloride is extended trans planarand again the molecular packing is determined by NR*-Cl hydrogen bonds.616Of particular significance to the development of crystal structure analysisis the determination of the structure and stereoconfiguration of panamine(38), since it was determined by direct methods. The molecule is composedof six-membered puckered rings, five of which have the chair conformation.61eThe structure of dihydrolycorine hydrobromide has been shown to be(39) (ref.517). An X-ray analysis of a new type alkaloid, daphniphyllineMeMehydrobromide,61s is shown in (40), while a novel type of framework (41) hasbeen found in an alkaloid from daphniphyllum macr~podum..~~~ It consistsof two cage-structures linked by a flexible carbon-carbon chain, the largercontaining two clisir-shaped and one boat-shaped six-membered rings fusedtogether with two five-membered rings, and the smaller one chair-shapedE. Hohne, I(. Schreiber, H. Ripperger, and H.-H. Worch, TetruWron, 1966,‘lnH. Shiro, T. Sato, H. Koyama, X. Maki, K. Nakanishi, and S. Uyeo, Cbm.61* G. Ferguson, J. A. D. Jeffreys, and G. A. Sim, J .Chem. SOC. ( B ) , 1966, 454.114 E. Giglio, A. M. Liquori, R. Puliti, and A. Ripamonti, A& Cry&., 1966, 20, 652.E. Giglio, A. M. Liquori, R. Puliti, and A. Ripamonti, Acta Cryst., 1968, 20, 683.616 I. L. Karle and J. Karle, Tetrahedron Letters, 1966, 1669.617 M. Shiro, T. Sato, and H. Koyama, Chem. and Id., 1966, 1229.11* N. Sakabe and Y. Hirata, Tetrahedron Letters, 1966, 965.618 N. Kamijo, T. Nabno, Y. Terao, and K. Oeaki, Tetrahedron Letter4 1966, 288922, 673.Cmm., 1966, 97756 CRYSTALLOBRAPRY8ix-membered ring and one five-membered ring. The structural formula, pro-pomd & present is C,,H,O,NCH,+I-. The stereochemistry and absoluteconfiguration of leurocristine methiodide dihydrate has been determined andprovides the structure of the antileukemia agent leurocristine and the on-colytic alkaloid vincaleukoblastine.Again, this structural analysis is par-ticularly interesting because of the new methods of determining molecular8tructures using anamalous dispersion methods.s20 In vertaline, the ringfusion in the quinolizidine ring is cis and the lactone group and the biphenylether are linked to the quinolizodine ring in the axial and equatorial positionTectively.621 Preliminary results of the structure of rauvoxinine are con-sistent with Pousset and Poisson’s earlier re~ults.5~~ Z-Allyl-2’-hydroxy-6,9-dimethyl-6,7-benzomomorphan hydrobromide monohydrate is a three-ringsegment of the morphine nucleus with the same conformation as the comes-panding part of morphine. It is T-shaped, has three asymmetric carbonatoms but the iminoethano-system is geometrically constrained to a cis-fusionSO that only two enantiomorphic pairs can be constructed without anunacceptable atrain.523Natural Phenolic Molecules.-X-Ray analysis of the dibromo-derivativeof the decametholether hopeaphenol has confirmed the structure as a poly-hydric phenol.The molecule can be regarded as being made up of fourunits of 3,5,P-trihydroxy~tilbene.~2~ The structure of xylerythrin 625 hasbeen shown to be as in (42). Periodate oxidation studies, n.m.r. spectra ofderivatives and X-ray crystallographic data have shown that plicatic acid,the major component of the heartwood extractive of western red cedar(Thuju plicata Donn) is 2,3,6-trihydroxy-7-metho~y-2-hydroxymethyl-4-(3’,4’- dihydroxy-5‘-met hoxyp heny1)tetralin- 3 - carboxylic acid.The asym-metric configuration, by X-ray data, is 2R, 35, 423, or its e n a n t i ~ r n e r . ~ ~ ~Novel Natural Products.-2-Amino-ethylphosphonic acid @-ciliatine hasa zwitterionic structure with a trans-configuration around the central methyl-m e linkage. Both the crystal structure and the hydrogen bond system almostduplicate those of 2-amino-ethanolphosphate, NH,+-CH2-CH2-P03H-although the latter molecule possesses a cis-configuration around the methyl-ene linkage.527 The direct determination of the structure of hydrolysedcocarboxylase has been made by the symbolic addition method, the para-meters being similar to those found in vitamin B,.628 Both the structureand absolute configuration of gliotoxin and the absolute configuration ofsporidesmin have been directly determined.629 Several features are par-ticularly noteworthy, in particular the geometry of the 1,3-cyclohexadiene‘ao J.W. Moncrief and W. N. Lipscomb, Ada Cryst., 1966, 21, 322.‘1’ C . Pascard-Billy, Compt. r e d . , 1966, 262, C, 197.ma W. Fedeli, Q. GiacomelIo, S. Cerrini, and A. Viciago, Chm. C m . , 1966, 608.ssQ P. Coggoa, T. J. King, and S. C. Wallwork, Chem. Cmm., 1966, 439.8. Ahhamsson and M. h s , Acta Chem. S m d . , 1965, 19, 2246.J. A. F. Gardner, E. P. Swan, S. A. Sutherland, and H. MacLean, Cancad. J . +?%em.,J. A. Hamilton and L. K. Steinrauf, Te&ahdron Letters, 1966, 6121.1966, eB, 52.m7 Y. Okaya, Ada Cryat., 1966, 20, 712.688 I.L. Karle and K. Britts, Ada Cryst., 1966, 20, 118.699 A. F. Beecham, J. Fridrichsons, and A. McL. Mathieson, Tetrahedron Leltm8,1986, 3131QERLOCH AND MASON 757system and the 1,l -disulphide bridge 2,Ei-piperizine dione system. Thestereochemistry of the aci-isomers of the ergot alkaloids of the peptide typewas determined by an X-ray analysis of the p-iodobenzoylamino-derivative,the structure being mtablished as (43); both five-membered rings adopt theenvelope conformation, and there is an interesting intramolecular OH- -t-;0(4 3)benzene hydrogen bond, the proton-benzene distance being approximately2.1 A.530 The structural analysis of verrucarin A p-iodobenzenesulphonateallows the constitution and absolute stereochemistry of verrucarin A andthe antibiotic metabolite of Myrthecium varrucuria to be established (44).5s1The derivative of a toxic substance teleocidin B produced by some strepto-myces has been shown to have a substituted indole nucleus with a nine-membered lactum ring.532 Dihydroteteleocidin B monobromoacetate 635has the molecular formula shown in (45).The structure of dimethyl micro-coccinate, C24H1,N505S4, in the form of its bis-Fbromoanilide, has beendetermined.534 The analysis shows conclusively that the molecule consistsof an extended heterocyclic ring system, with three of the four thiazolerings bonded directly to the pyridine nucleus. The two 2,4'-linbed thiazolerings are coplanar within the limits of accuracy. An interesting structuraldetermination is that of l a ~ r e n c i n , ~ ~ ~ which is the first algal natural productcontaining bromine.The relative stereochemistry is shown in (46).Formycin consists of pyrazolo[4,3-d]pyrimidine base and ribofwanomresidues which comprise a nucleoside-like molecule. Formycin B has thestructure (47). The pyrazolopyridine base and its exocyclic amino-groupare coplanar, the ribose ring being puckered.536 An X-ray analysis of theantibiotic blasticidin S has been determined 537 through an analysis of theS monohydrobromide, the molecular framework being shown in (48). Thestructures of both tetradonic acid hydrobromide and diacetylanhydrotetra-dotaxin hydroiodide (49) have been determined and possess an adamantane-A. T. McPhail, 0.A. Sim, A. J. Frey, and H. Ott, J . Chem. Soc. (B), 1966, 377.'*l A. T. McPhail and G. A. Sim, J . Chem. SOC. ( C ) , 1966, 1394.N. Sakabe, X. Hirata, Y. Tomiie, and I. Nitta, Bull. Chem. Soc. Japan, 1966, 89,mS N. Sakabe, H. Harada, Y. Hirata, Y. Tomiie, and I. Nitts, Tetrahedron Letters,684 M. N. G. James and K. J. Watson, J . Chem. Soc. (C), 1966, 1361.A. F. Cameron, K. K. Cheung, G. Ferguson, and J. M. Robertson, Chem. Comm.,0. Koyama, K. Maeda, H. Umezawa, and Y. Iitaka, Tetrahedron Letters, 1966,1773.1966, 2523.1966, 638.697.m7 S. Chuma, Y. Nawata, and Y. Saito, BUZZ. Chem. SOC. Japan, 1966, 89, 1091758 CRYSTALLOGRAPHY(44)Ho:iH Y (47)7' NH2 NH.~H U I(48)OH OHOHOH OR(4 9)like cage configuration. 538 In cycloalliin hydrochloride monohydrate, thesulphoxide-oxygen is axial and the methyl group is equatorial.The six-membered ring has the chair conformation and the absolute configurationderived with the knowledge that the configuration about C(3) is L . ~ ~ ~ In anasymmetric derivative of 1,4-oxathian S-oxide, the sulphoxide group is foundto be cis to the hydroxymethyl group or its anantiomer for sulphoxide A.The absolute configuration of sulphoxide A is established and the chairconformation is somewhat di~torted.~~oBiological lKolecules.-The crystallographic studies of the enzymicproperties of lysozyme are being extended to investigations of the bindingof various substrates of which tri-N-acetyl-chitotriose is the largest. It isclear that small conformational changes in the enzyme molecule can be recog-nised. The structural studies of carboxypeptidase A have now been takento the point where the molecular shape (approximately 52 x 4-4 x 40 A), aprobable tracing of the polypeptide chain, estimation of the helical contentas 25%, and the direct location of the zinc atom have been achieved.It is188 C. Tamura, 0. Amakasu, Y. Sasada, and K. Tsuda Acta Cryst., 1966,20,219,226.'he K. J. Palmer and K. S. Lee, Acta Cryst., 1966, 20, 790.K. W. Buck, R. A. Hamor, and D. J. Watkin, Chem. Cornm., 1966, 769GERLOCH AND MASON 759clear that near the zinc atom, there is a pocket which might accommodatehydrophobic side groups of inhibitors and s~bstrates.5~1 The moleculararrangement in 2Zn-insulin and 4%-insulin has been shown to be verysimilar, the relationship of the molecular two-fold axis in insulin t o crystallo-graphic symmetry axes being determined.542 X-Ray analyses have beenmade of derivatives of a-chromotrypsin inhibited with di-isopropylfluoro-phosphate and a number of sulphonyl fluoride inhibitors.The positions andorientations of the inhibitor groups were derived from single isomorphousheavy atom derivatives.643 The axial residue distances (in poly-ccy-benzyl-L-glutamate, poly-as-benzoxycarbonyl-L-lysine, and poly-a-1;-glutamic acid)in solution are in good agreement with the a-helix arrangement as derivedfrom the small angle X-ray scattering eviden~e.~~4 Electron density syn-theses for the orthorhombic form of the crystalline lithium salt of DNAhave been calculated, phases being derived by model building and Fouriertransform methods.Some refinements of the DNA model have been com-pleted and the structure in the region between the DNA molecule discussedwith the possible relation to water molecules.545 X-Ray diffraction studiesof double helical RNA have led to suggestions of the way in which helicalregions in RNA molecules may play an essential part in protein synthesis.646The arrangement of protein sub-units and distribution of nucleic acid inturnip yellow mosaic virus have been very carefully studied by both X-rayand electron microscope methods. The previous conclusion, that the overall(low resolution) symmetry of the ordering of the RNA within the virusparticle was lower than that of the protein, is shown to be wrong.The data,point to the icosahedral surface lattice T = 3 corresponding to 180 proteinsub-units. A significant proportion of the RNA is deeply embedded withinthe protein shell and the mode of winding of a single RNA chain is such thatlarge segments of it are closely associated with the rings of 6- and 5-proteinstructure units which make up the protein she11.547A number of reports have dealt with the general crystallographio pro-cedures involved in an analysis of proteins. A n exact expression for thesquare of the structure factor of the heavy atom in terms of other measure-able quantities has been derived and a method of placing the two sets ofdata Elp and FHP on a common scale ~uggested.~~a Methods have beenproposed by which isomorphous replacement and anomalous scatteringmeasurements may be combined to locate anomalously scattering heavyatoms in protein structures.549 Both Patterson and Fourier methods are541 W.N. Lipscomb, J. C. Coppola, J. A. Hartsuck, M. L. Ludwig, H. Muirhead,J. Searl, and T. A. Steitz, J . MoZ. Biol., 1966, 19, 423.648 M. M. Harding, D. C. Hodgkin, A. F. Kennedy, A. O’Connor and P. D. J. Weitz-mann, J . Mol. BWZ., 1966,16,212; E. Dodson, M. M. Harding, D. C. Hodgkin, andM. (3.Rossmann, ibid., p. 227.54s P. B. Sigler, B. A. Jeffrey, B. W. Matthews, and D. M. Blow, J . MoZ. Biol., 1966,15, 175.644 P. Saludjian and V. Luzzati, J . Mol. BWZ., 1966, 15, 681.6 p 6 D. A. Marvin, M. H. F. Wilkins, and L. D. Hamilton, Ada Cryst., 1966,20, 663.64b S. Arnott, F. Hutchinson, M. Spencer, M. H. F. Wilkins, W. Fuller, and R.5 4 7 A. mug, W. Longley, and R. Leberman, J . Mol. BioZ., 1966, 15, 315.648 A. K. Singh and S . Rama,seshan, Acta Cryst., 1966,20, 279.E . ~ @ B. W. Matthews, Ada Cryst., 1966, 20, 230.Langridge, Nature, 1966, 211, 227760 CRYSTALLOGRAPHYdiscussed and examples are given to illustrate the use of the new methods.Examples show how the relative co-ordinates of heavy-atom groups indifferent derivatives may be determined and how the absolute configurationof these co-ordinates may be established. Kartha has shown 55* how, bysuitably combining the difference in amplitudes between the free proteinand its heavy-atom derivative with the difference between the Friedel pairs€or the heavy-atom derivative, it is possible to obtain a quantity representingthe length of the heavy-atom vector. This quantity, computed purely fromexperimental data, could be used in applying the usual least-squares tech-niques for refining the positional and thermal parameters of heavy atoms inprotein derivatives. A procedure intended as an intermediate step betweenthe interpretation of a E'ourier map of medium resolution and the finalrefinement of such a molecule as a protein has been 0utlined.5~~ The pro-cedure builds a representation of a polypeptide suitably flexible by rotationsabout single bonds and any other lines. It uses least squares to fold theresulting chain and side chains to approach the best interpretation of theelectron density or other criterion. The logical extension of this kind ofwork is, of course, the a priori prediction of molecular conformation inbiomacro-molecules from a simple knowledge of the amino-acid sequence.The theoretical study of the least-squares refinement of flexible long-chainmolecules, with special reference to cr-helical structures has also been given. 552The conformation of side groups in amino-acids and peptides has been dis-cussed.553 The length of the bond U-CY is not different from the standardvalue of 1.54 A, but the angle C"-@-CY is larger than the tetrahedral value,with a mean value of 114". The CY atom occurs close to one of three possiblepositions, fairly well represented in different side groups, one trans and twogauche about the Ca-@ bond, with respect to the amino-nitrogen. Thereare different side group conformations in two modifications of L-argininehydrochloride, other bond lengths and bond angles being very similar. Theimportance is suggested of studying a number of derivatives of amino-acidsand peptides to obtain a knowledge of common types of side-group conforma-tions.554 The dimensions of the amino-acid group in L-valine hydrochlorideare, in general, similar t o those reported for related molecules. The nitrogenatom is substantially out of the plane defined by two oxygens and two carbonsand is similar to that in lycine, glycine, and a r g i r ~ i n e . ~ ~ ~ A very carefulanalysis has been completed for L-alanine. The structure bears a strikingresemblance to that of DL-alanine and involves the use of all available protonsin N-He-0 hydrogen bonds, which range from 2-81-2.85 A separaterefinement of the L-alanine structure has been carried out. There are somesignificant differences between the two analyses and the whole question ofthe weighting scheme in the least-squares analysis is considered.557C. Kartha, Acta Cryst., 1965, 19, 883.mi1 R. Diamond, Acta Cryst., 1966, 20, 253.u* R. Diamond, Acta Cryst., 1965, 19, 774.B53 (3. N. Ramachs~dran and A. V. Lakshminarayan, Biopolymers, 1966, 4,495.556 R. Parthasarthy, Acta Cryst., 1966, 21, 422.6~ H. J. Simpson, jun., and R. E. Marsh, Acta Cyst., 1966, 20,650.567 J. D. Dunitz and R. R. Ryan, Acta Cryst., 1966,.21, 617.U. N. Ramachandran, S . K. Mazumdar, K. Venkaresan, and A. V. Lakshmka-rayanan, J . Mol. Biol., 1966,15, 232GERLOCH AND MASON 761Taurine, 2-aminoethylsulfonic acid, has a zwitterion configuration withthe formula NH,+-CH,-CH,-SO,-. The amino- and sulfonate-groupsassume a gauche configuration around the central methylene linkage.5sgThe tram form of 4-aminomethylcyclohexanecarboxylic acid has the di-equatorial conformation, the environment of the nitrogen atom being nearlytetrahedral.559 X-Ray data for polyglycine 11 have been discussed and anexplanation offered for the union of three polypeptide chains in a triple helix,with linking of one to the other through interchain hydrogen bonds.560The molecular structure of 5-ethyl-6-methyluracil is closely related tothat of thymine monohydrate. The pyrimidine ring is significantly non-planar being buckled apparently to relieve strain between substituent groups.Two pairs of N-H***O hydrogen bonds 2.78 and 2.82 A hold the moleculestogether in the lattice to form chains.561 The disodium salt of 2,4,6,8-tetra-hydroxypyrimido [ 5,4- d]p yrimidine (2 , 6,8,10- tetrahydroxyhomopurine) isformed by the neutralisation of the two p-hydroxy-groups. The moleculeis planar but only partly aromatic, the oxygen atom being in the carbonylform. The G-C central bond has high double bond character, the otherG-C having high single-bond character; G-N distances vary from1.37-1.40 8. The sodium ions have an octahedral co-ordination with threeoxygens from water molecules and three from homopurine molecules. 662Adenosine 3‘-phosphate &hydrate (adenylic acid b) exists as a zwitterionwith one nitrogen of the purine protonated by a phosphate proton. Theangle between the base and the ribose is displaced by more than 0.5 A fromthe plane of the remaining ring atoms and on the same side as C(5). Theorientation of the C(5)-C(5’) bond is unusual in that it is trans to C(3’)-C(4‘)and gauche to O(l‘)-C(4‘). It is of interest that one of the water moleculesdisplays a planar nearly trigonal hydrogen-bonded pattern while the other isinvolved in a highly distorted tetrahedral hydrogen- bonding scheme.663The comparison 564 of the structures of 5-bromodeoxyuridine and 5-bromo-uridine with other nucleosides and nucleotideS shows that the glycosidicbond length in BUDR is shorter than normal and the conformation of theC(5’)-C(5’) bond is not that most commonly found. In BUR, the glycosidicbond length and the C(5’)-O(5’) conformation is normal. The complex of2-amino-9-ethylpurine and 5-fluoro-l-methyluracil is a hydrogen-bondedplanar complex. The purine and pyrimidine bases are joined by twohydrogen bonds, N-Ha-0 (amino-group of 2-aminopurine to carbonyloxygen) and an N-Hv-N betveen the ring nitrogens of 2-aminopurine andthe nitrogen of fluorouracil. The base pairing structure resembles theWatson-Crick pairing ~onfiguration.~~~ In the intermolecular complex,9-ethyladenine,l-methyl-5-bromouraciIy two hydrogen bonds are found658 Y. Okaya, Acta C ~ y s t . , 1966, 21, 726.660 P. Groth, Acta Chem. Scand., 1966, 20, 1321.6 * o G. N. Ramachandran, V. Sasisekharan, and C. Ramakrishnan, Biochem., Biophy8.661 G. N. Reeke, jun., and R. E. Marsh, Acta Cryst., 1966, 20, 703.M. Brufani, G. Casini, W. Fedeli, G. Giocomello, and A. Vsciago, J. Chem. SOC.563 M. Sunderalingam, Acta Cryst., 1966, 21, 495.664 J. Iball, C. H. Morgan, and H. R. Wilson, Nature. 1966, 209, 1230.m5 H. M. Sobell, J . Mot. Biol., 1966, 18, 1.Acta, 1966, 112, 168.( A ) , 1966, 639762 CRYSTALLOGRAPHYbetween the adenine and uracil derivatives involving uracil-O(Z) and -N(3)and adenine-N(6) and -N(7). Pairs adjacent to each other are linked intoinfinite ribbon-like structures between uracil-0(4) and ade11ine-N(6).~~~The 2 : 1 crystalline complex between 1,3,7,9-tetramethyluic acid and3,4-benzpyrene, of interest in considerations of the possible interactionsbetween carcinogenic hydrocarbons and biologically important molecules,has been analysed.667&'* L. Katz, I(. Tomita, and A. Rich, Acta Cryst., 1966, 21, 754.A. Damiani, E. Giglio, A. M. Liquori, R. Puliti, and A. Ripamonti, J. MoZ. BioZ.,1966, 20, 211