2 Part (iv) X-RAY CRYSTALLOGRAPHY By George Ferguson (Department of Chemistry The University of Glasgow Glasgow W.2 Scotland) OF the new text books which reflect the growing interest of organic chemists in crystal structure determination that of G. H. Stout and L. H. Jensen’ is noteworthy for its clear and detailed description of organic crystal structure determination. A new monograph by L. V. Azaroff2 also deals thoroughly with the theory and practice ofcrystal structure determination and in its later chapters gives a careful account of powder diffraction methods. A feature of an in- creasing number of papers is that ‘direct’ methods of phase determination which do not depend on the presence of a ‘heavy’ atom are being used for the analysis of both centrosymmetric and non-centrosymmetric crystals.Absolute configuration determination is also receiving attention and a second reference list of organic structures whose absolute configurations have been determined by X-ray methods has a~peared.~ Limitations on space have made it impossible to report all crystallographic papers published in 1968 and many have had to be left out of this report or given limited coverage. As in the 1967 Annual Report papers which give only brief details of constitution of e.g. natural products will be reported in other chapters and have been omitted here. In the account that follows details of bond lengths etc. are given where these are differences from ‘accepted’ values ;4 estimated standard deviations are given where appropriate in parentheses in units of the least significant digit of the quantity to which they refer.Carboxylic Acids and Related Compounds.-The geometry of hydrogen bonding in carboxylic acids which do not form centrosymmetric dimers has been surveyed’ and four main features are pointed out. (i) The identification of the carboxy oxygen atoms as to which is carbonyl and which is hydroxy is A usually unambiguous on the basis of reo < rCOH and C-C-OH < C-O. (ii) Deviations of acceptor oxygen atoms from the mean planes of the carboxy-groups lie between 0.051 and 0.379 8,;none is as large as the 0-549 8 reported for a centrosymmetric dimer by Jeffrey and Sax.6 The largest rotation of the 0* -* 0vector out of the carboxy-plane is only 8”.(iii) The acceptor oxygen atoms in the synplanar O=C-OH..-O system have C-OH...O G.H. Stout and L. H. Jensen ‘X-Ray Determination-A Practical Guide,’ Macmillan New York 1968. L. V. Azaroff ‘Elements of X-Ray Crystallography,’ McGraw-Hill New York 1968. F. H. Allen S. Neidle and D. Rogers Chem. Comm. 1968,308. Chem. Soc. Special Publ. No. 18 1963 41. J. Donohue Acta Cryst. 1968,24 B,1558. ‘G. A. Jeffrey and M. Sax Acta Cryst. 1963 16,430. George Ferguson angles in the range 1085 to 131.9".(iv) There is no apparent regularity with regard to the positions of the donor OH groups most of which are not even approximately synplanar and the angles C=O.*.HO range from 118.8 to 168". It follows that invocation of sp2 hybridization and localised electron pairs to explain the planarity of centrosymmetric carboxylic acid dimers is unnecessary and that in the case of some acids which do not form dimers this theory leads to the wrong prediction.The hydrocarbon chain of DL-2-methyl-7-oxododecanoicacid7 is bent at C(2) and the methyl group forms a continuation of the zig-zag backbone; conformations of this type are common in methyl branched fatty acids. The chain is also twisted 7"at the keto-group. The mean C-C distance 1-51l(11) 8 and C-C-C angle 114.2(7)"are systematically shorter and larger respectively than normal and are explicable in terms of thermal anisotropy and rotatory oscillations of the chains about their long axis. The structure of the cr-form of brassylic acid CO,H(CH,) 1C02H has been determined' and compared with the structure ofpirnelic(C,) azelaic (C9) and undecanoic (C dicarboxylic acids.These acids have a constancy of molecular conformation in particular of the carboxy-groups and hydrogen bonds and a characteristic form of packing. Interest in systems with 'very short" hydrogen bonds continues. Hydrazinium hydrogen oxalate has been studied by X-ray" and neutron" diffraction and the results are in good agreement ;the hydrogen oxalate ions are linked end-to- end by short hydrogen-bonds determined as 2.450(4)A by X-rays and 2.448(7) 8 by neutrons. These bonds are either truly symmetrical or have statistically disordered hydrogen atoms. Other X-ray analyses of acid salts also thought to contain genuinely symmetrical 0* * H - - - 0 bonds include potassium hydrogen bisphenylacetate [O-.H...02-443(4)A],12 potassium hydrogen di-p-hydroxy- benzoate hydrate [2.458(6) potassium hydrogen malonate [2.459(7) 8,],14 and potassium hydrogen di-p-methoxybenzoate [2.476( 18) A].' In all these examples the oxygen atoms involved in the O..-H..-Obonds are crystallo- graphically equivalent being related by either two-fold axes or centres of symmetry. In potassium hydrogen diformate however,' two crystallographic- ally non-equivalent formate groups are linked into a dimer by a short possibly symmetrical hydrogen-bond with 0.* 0 2-447(6)A. There are no short sym- metrical hydrogen-bonds in the crystal structure of potassium hydrogen gly- collate. The absolute configuration of the biologically active isomer ( +)-isocitric ' A.M. O'Connel Acta Cryst. 1968,24 B 1399. * J. Housty Acta Cryst. 1968 24 B 486. J. C. Speakman Chem. Comm. 1967,32. lo N. A. K. Ahmed R. Liminga and I. Olovsson Acta Chem. Scad. 1968,22,88. A. Nilsson R. Liminga and I. Olovsson Acta Chem. Scad. 1968,22 719. L. ManojloviC and J. C. Speakman Acta Cryst. 1968,24 B 323. l3 L. ManojloviC Acta Cryst. 1968 24 B 326. l4 G. Ferguson J. G. Sime J. C. Speakman and R. Young Chem. Comm. 1968,162. l5 D. R. McGregor and J. C. Speakman J. Chem. SOC.(A),1968,2106. l6 G. Larsson and I. Nahringbauer Acta Cryst. 1968,24 B 666. R. F. Mayers E. T. Keve and A. C. Skapski J. Chem. SOC.(A),1968 2258. X-Ray Crystallography acid has been determined as (1R :2S)-l-hydroxy-1,2,3-propanetricarboxylic acid from an investigation of its potassium dihydrogen salt.'* The ion is fully extended and it is the central carboxy-group which is ionised.Three tartrates odium,'^ calcium and strontium,20 have been examined as part of a study of the conformation of the tartrate ion in the crystalline state; the two halves of the ions each consisting of a carboxy-group a tetrahedral carbon and a hydroxy oxygen atom are individually planar. Two crystalline modifications of DL-a-aminobutyric acid have been studied.2 In the monoclinic form the y-carbon atom is distributed mainly among three positions corresponding to the three rotational isomers trans gauche (I) and gauche (II) with respect to the nitrogen atom; in the tetragonal form the y-carbon is located only at the trans-position.The conformation of the a-form of a-glycylglycine kH3 CH CO NH -CH -COY is different from that found for the p-form;22 there is an angle of 22" between the plane of the amide group and that of the carboxy-group in the a-form whereas in the p-form these groups are coplanar. The distortion in the a-form presumably permits better packing and stronger hydrogen-bonds and van der Waals interactions. In the asym- metric unit of crystals of L-cysteine there are two independent molecules which NH.PO,H, I C=NH I CH,-N-CH2COOH l8 D. van der Helm J. P. Glusker C. K. Johnson J. A. Minkin N. E. Burow and A. L. Patterson Acta Cryst. 1968 24 B 578. l9 G. K. Ambady and G. Kartha Acta Cryst. 1968,24 B 1540.2o G. K. Ambady Acta Cryst. 1968,24 B 1548. 21 T. Ichikawa and Y. Iitaka Acta Cryst. 1968,24 B 1488. T. Ichikawa Y. Iitaka and M. Tsuboi Bull. Chem. SOC.Japan 1968,41 1027. 22 A. B. Biswas E. W. Hughes B. D. Sharma and J. N. Wilson Acta Cryst. 1968 24 B 40; E. W Hupheq. Actn Crw. 1968. 24. B. 1 128 George Ferguson occur as zwitterions HSCH *CHNH3*CO; .23 The bond lengths and angles are not significantly different from each other or from accepted values but their conformations differ by twists of 118" around the C(a)-C(p) bond and 33" around the C-C(a) bond. In L-aspartic acid the ionised and non-ionised carboxy-groups can be clearly distinguished showing the zwitterion to be O,C* CHhH CH C02H.24Thetrans-isomerof4-aminomethylcyclohexane-carboxylic acid which exhibits strong antifibrinolytic activity.has the zwitterion in the di-equatorial c~nformation.~' N-Phosphoryl creatine (11 a biological high-energy phosphate serves as an energy reservoir in vertebrate muscles and crystals of its disodium salt have been examined.26 The guanidino-group is planar and all hydrogen atoms available for hydrogen bonding are used. Observed differences between bond distances found in (1)and in creatine are not significant and the structural basis of the instability of (1) remains unresolved. 0-Carbamoylhydroxylamine OC(NH,)*ONH, is planar with the exception of the hydrogen atoms of the 0-bonded amino-gr~up.~~ The amide group of NN-diphenylacetamide is planar and the two phenyl rings are inclined at 62" (ring nearest oxygen) and 77" to the amide plane.28 The atoms of the ester groups of the centrosymmetric molecule 1,1,2,2-tetracarbomethoxyethaneare planar in the crystalline state in agreement with vapour and liquid-phase investigation^.^^ The octabutyrate C,4H,4Br40 obtained from condensation of resorcinol and p-bromo- benzaldehyde and acylation of the phenolic product has structure (2).30The four carbon atoms linking the aromatic rings are nearly coplanar and the bromo- phenyl groups are all directed to the same side of that plane.The carbanion in potassium 4,4-dinitro-2-butenamide is essentially planar and the NCN bond angle is 120" in spite of an O...O distance of only 2.51 8 between the nitro- groups.31 Chloro- and bromo-cyanoacetylene form linear chain structures with N C1 and N --Br distances of 2.970(8)and 2-956(18) A re~pectively.~~ Bonded distances for the chloro- and bromo-compounds are respectively :C-halogen 1.634(9) 1*766(15); CsC 1*176(12) 1*190(21); =C& 1.382(13) 1*399(22); -C=N 1.133(13) 1.113(24)A.The shortening of the C=N distances from the value 1.158(1) for gaseous cyanides appears to be real when compared with similar non-metallic cyanides where the nitrogen is involved in donor-acceptor interaction. Molecules of bigeranyl tetrahydrochloride (2,6,11,1S-tetrachloro-2,6,11,15-tetramethylhexadecane)are almost planar centro~ymmetric.~~ The carbon chain is bent at the tertiary carbon atoms thereby achieving a pro- *' M. M. Hardincg and H. A. Long. Acta Cryst..1968. 24. B. 1096. 24 J. L. Derissen H. J. Endeman and A. F. Peerdeman Acta Cryst. 1968,24 B 1349. 25 P. Groth Acta Chem. Scad. 1968,22 143. 26 J. R. Herriott and W. E. Love Acta Cryst. 1968,24 B 1014. 27 1. K. Larsen. Actn Chm. Scnnd.. 1968. 22. 843. 28 W. R. Kngbaum R.-J. Roe and J. D. Woods. Acra Crvr.. 1968. 24. B. 1.704. 29 J. P. Schaefer and C. R. Costin J. Org. Chern. 1968,33,1677. 30 B. Nilsson Acta Chem. Scad. 1968,22 732. 31 J. R. Holden and C. Dickinson J. Amer. Chem. SOC. 1968,90,1975. 32 T. Bjorvatten Acta Chem. Scad. 1968,22,410. 33 F. Mo and H. Serrum Acta Cryst. 1968,24. B 605. X-Ray Crystallography 45 nounced Z-shape. The C-Cl bonds pointing out of this plane are abnormally long [mean 1-857(7) A] ;the main reason for this is believed to be short intra- molecular Cl-H approach distances.The C1-C-C angles are in the range 105.3-107.6(4)". Substituted Benzene and Polycyclic Aromatic Compounds.-The carboxy-group in rn-bromobenzoic acid is almost exactly coplanar with the benzene ring34 unlike that of the ortho-substituted derivative. The crystal structure of o-aminobenzoic acid contains two non-equivalent molecules one neutral and the other a zwitterion. In both the carboxy-group is rotated about the exocyclic C-C bond.35 The nitro-group in 3-nitroperchlorylbenzeneNO2 C6H4 C10 is rotated 13" from the plane of the aromatic ring and decreased. resonance interaction contributes to a long C-N distance of 1.497(10) A; the C-C1 distance 1*786( 10) A is also long compared with that for a C-Cl bond where the chlorine is uns~bstituted.~~ Another effect noted is that the C-C-C angles [124.1 and 126-1(6)"] at substituted carbon atoms are significantly greater than 120".2,6-Dimethyl-4-methoxylbenzonitrile N-oxide is planar apart from the methoxy-carbon atom with the C-N-0 bond angle reported as 178.3(6)". The bond lengths in the C-C-N-0 chain are 1.435 1.147 and 1-249(8) A respectively and compare with MO predi~tion.~'The catechol moiety in the hydrochloride of dopamine 3,4-dihydroxyphenylethylamine is planar and the C-N distance agrees well with the average value 1.503 A for C-GH bonds in a-amino-a~ids.~~ When pale yellow crystals of 2-(2',4'-dinitrobenzyl) Br Ph (3) (4 1 pyridine (3) are irradiated with light of 4000 A or less a deep blue substance is produced by what is believed to be a reversible tautomeric reaction.The methylene hydrogen atoms in (3)are presumably the most acidic in the structure and the most likely to be involved in the tautomerisation reaction. In crystals of (3) the intramolecular C-C-C angle between the two aromatic rings is 114" and the closest approach of a methylene hydrogen atom to an electronegative atom is intramolecular to an oxygen (at 2.4 A) on the o-nitro-group. This nitro- group is rotated 32" and the other through 12" from the benzyl plane. It is suggested that the tautomerisation is probably intramolecular and begins 34 N. Tanaka T. Ashida Y. Sasada and M. Kakudo Bull. Chem. SOC.Japan 1967,40,2717. 35 C. J. Brown Proc.Roy. SOC. 1968 A 302,185. 36 G. J. Palenik J. Donohue and K. N. Trueblood Acta Cryst. 1968,24 B 1139. 37 M. Shiro M. Yamakawa T. Kubota and H. Koyama Chem. Comm. 1968,1409. R.Bergin and D. Carlstrom Acta Cryst. 1968,24 B 1506. George Ferguson with the transfer of a methylene hydrogen atom to an oxygen of the o-nitro- group leaving the two rings interconjugated. This hydrogen atom might then be transferred intramolecularly to the pyridine nitrogen atom.39 Complete details of the structure of 2,4,6-trinitrophenetole have appeared4' and also those of its complexes with caesium and potassium ethoxide4' (Meisenheimer salts) M+[C,H,(NO,),(OEt),] -. In both complexes the two equivalent alkoxy-groups are attached to the same carbon atom which attains tetrahedral configuration with mean C-C-C angle 107" ; the six-membered ring retains planarity.The intramolecular strain in 1,2,4,5-tetra-t-butylbenzene is relieved by angle deformation rather than out-of-plane distortion of the ring.42 The molecule has a crystallographic centre of symmetry and mutual repulsion of the o-butyl groups increases the appropriate angles e.g. C(2)-C(l)-C(butyl) at C(1)and C(2) to ca. 130". Since the aromatic ring stays planar the internal angle at C(3) is also increased to 130". The bonds connecting the t-butyl groups to the ring are long (1.567 A) compared with similar bonds in other compounds and this may also be an overcrowding effect. Crystals of chloropentamethylbenzene exhibit an orientational disorder the chlorine atom and methyl groups being distributed in six possible positions.43 All benzene rings in hexaphenylbenzene are essentially planar but the molecule is distorted as a result of out-of-plane bending of exocyclic The non-centrosymmetric molecule adopts a propeller like conformation with approximate six-fold symmetry ; the peri- pheral rings are not perpendicular to the central ring but are twisted about 25" from this position and the CLC bridge distances vary from 1.473 to 1-531(13) A).Another polyphenylbenzene slightly less overcrowded is obtained on dimerisation of the 3-bromo-2,4,6-triphenylphenoxyl radical and has structure (4).45 HO 39 K. Seff and K. N. Trueblood,Acta Cryst. 1968,24 B 1406. 40 C. M. Gramaccioli,R. Destro and M. Simonetta,Acta Cryst.1968 24 B 129; Chem. Comm. 1967. 331 ;Ann. Reports. (B),1967 72. 41 R. Destro C. M. Gramaccioli and M. Simonetta,Acta Cryst. 1968 24 B 1369; c$ H. Ueda N. Sakabe J. Tanaka and A. Furusaki Nature 1967,215,956; Ann Reports (B),1967,72. 42 k van Bruijnsvoort L. Eilermann H. van der Meer and C. H. Stam Tetrahedron Letters 1968,2527. " G.-P. Charbonneau and J. Trotter J. Chem SOC.(A) 1968 1267. 44 J. C. J. Bart Acta Cryst. 1968 24 B 1277. 45 R. Allmann and E. Hellner Chem. Ber. 1968,101,2522. X-Ray Crystallography Me Me The structures of 2'-fl~0r0-~~ and 2'-chlor0-4-acetyl-biphenyl~~have been reported. The angles between the phenyl rings are 51 and 49" respectively and the C(sp2)-C(sp2) single bonds are 1.479(10) and 1.490(10) A.Although no major o-substituents are present in 3,3'-dimeth~l-~~ and 3,3'-dichloro-4,4'- diamino-bipheny14' the phenyl rings are not coplanar but are inclined at 41 and 21" respectively. The C(sp2)-C(sp2)bonds are 1.504(13) and 1.515(24) A. In addition in each molecule each phenyl ring is bent through ca. 3" away from the line of C(1)-C(1'). Ellagic acid (5) the (centrosymmetric) dilactone of 2,2'-dicarboxy-4,S,6,4',S',6'-hexahydroxybiphenylis essentially planar only the lactone carbonyl groups being slightly tilted (3.6")from molecular plane." 8,16-0xido-cis-[2.2]metacyclophane (6)has the m symmetry demanded by its space group but the molecule has nearly mm symmetry and is folded to a dihedral form with an angle of 99-6" between the slightly boat-shaped benzene rings.51 The bond angle at the oxygen atom is 1014(4)O while the mean value of those in the methylene bridges is 119.0(5)".The strain implied by these values is consistent with the tendency of the compound to eject the hetero-atom and transform into the corresponding pyrene. A centre of symmetry is required of 4,12-di(bromomethyl)[2,2]metacyclophane (7) by its space group and the two benzene rings are displaced stepwise and slightly distorted to a boat-shape to accommodate the intramolecular overcrowding effects in this molecule52 as in 46 D. W. Young P. Tollin and H. H. Sutherland Acta Cryst. 1968,24 B 161. 47 H. H. Sutherland and T. G. Hoy Acta Cryst. 1968,24 B 1207. 48 S. A. Chawdhury A. Hargreaves and R. A. L. Sullivan Acta Cryst.1968,24 B 1222. 49 S. A. Chawdhury A. Hargreaves and S. H. Rizvi Acta Cryst. 1968,24 B 1633. 50 A. McL. Mathieson and B. J. Poppleton Acta Cryst. 1968,24 B 1456. 51 M. Mathew and A. W. Hanson Acta Cryst. 1968,24 B 1680. 52 M. Mathew. Acra Crvst.. 1968.24. B,530. 48 George Ferguson the parent 4,12-dimethyl deri~ative.’~ The CH,-CH bond length is 1.568(8) A which is comparable with 1-573 A in the parent and is also indicative of molecular strain. 9-Dicyano-2,7-dinitrofluorene (8) has two-fold (crystallographic) symmetry; the fluorene moiety is planar and the nitro-groups are rotated 17.6” b~t-of-plane.’~ The dicyanomethylene portion is rotated 2.3” about the formal double-bond almost exactly the same conformation as found in 9-dicyano-2,4,7-trinitrofluorene’’(which in addition has the fluorene moeity in a slight propeller conformation because of overcrowding at the 4-nitro-group).The seven-membered ring of dibenzo[b,f]tropone (9) is in boat conformation similar to that in cycloheptatriene with the two benzene rings inclined to each other at an angle of 39°.56 The serendipitous synthesis of (10) from a-phenyl- cinnamoyl chloride and its X-ray analysis have been rep~rted.’~ The novel reaction results in the formation of four new carbon-to-carbon bonds and structure (10) can be defined by two planes intersecting along the Ph-C-CH bond. Molecules of 9-anthraldehyde dimer lie on symmetry centres and hence the CHO groups are in the trans-configuration with respect to the anthracene ~keleton.’~ Each half-molecule is bent through an angle of 46” similar to that found in di-p-anthra~ene.’~ Tricarbonylchromium complexes of a number of aromatic hydrocarbons or their derivatives have been prepared and studied crystallographically including those of l-aminonaphthalene,60 anthracene,61 phenanthrene,62 and 9,lO-dih~drophenanthrene.~~ In the 1-aminonaphthalene complex the tricarbonylchromium moiety is located over the unsubstituted ring and the orientation of the carbonyl groups in all four complexes resembles the staggered conformation of benzenetricarbonylchromium.The anthracene phenan- threne and dihydrophenanthrene complexes have the chromium atom bonded to a side ring and small but significant lengthening of the C-C bonds in this ring is found ;there is however no suggestion of alternation of long and short bonds as a result of the complexing to chromium.3,5,8,10-Tetramethylaceheptalene(1 l) a hydrocarbon with a 14 x-electron system is planar except for the methyl hydrogen atoms;64 the bond distances and angles are in good agreement with quantum-mechanical predictions. Non-aromatic Carbocyclic Molecules-Bicyclopropyl adopts the trans con-53 A. W. Hanson Acta Cryst. 1962,15,956. 54 J. Silverman A. P. Krukonis and N. F. Yannoni Acta Cryst. 1968,24,8 1481. 55 J. Silverman A. P. Krukonis and N. F. Yannoni Acta Cryst. 1967,23 1057. 56 H. Shimanouchi T. Hata and Y. Sasada Tetrahedron Letters 1968,3573. 57 A. L. Bednowitz W. C. Hamilton R Brown L. G. Donaruma P. L. Southwick R Kropf and R k Stanfield J.Amer. Chem. SOC.,1968,90,291. 58 M. Ehrenberg Acta Cryst. 1968,24 B 1123. 59 M. Ehrenberg Acta Cryst. 1966,20 177. 6o 0.L. Carter A. T. McPhail and G. A. Sim J. Chem. Soc. (A),1968,1866. 61 F. Hank and 0.S. Mills J. Organometallic Chem. 1968 11 151. 62 K. W. Muir G. Ferguson and G. A. Sim J. Chem. SOC. (B),1968,467. 63 K. W. Muir and G. Ferguson J. Chem. Soc. (B) 1968,476. 64 E. Carstensen-Oeser and G. Habermehl Angew. Chem. 1968,80,564. X-Ray Crystallography formation in the crystal with 2/m symmetry; the average cyclopropyl C-C bond-length is 1.506(4)8 and the central bond 1-487(4) The C-C bonds in the cyclopropane ring of tri-isopropylidenecyclopropane(12) have length 1.44(1) 8, shorter than in bicyclopropyl because of the three ethylenic bonds radiating from the ring., Me Me 0 0 (16) (15) Cyclobutane rings occur in planar and puckered conformations in the solid state.Planar molecules are invariably found in centrosymmetric space groups with the molecular and crystallographic centres of symmetry coinciding. In the puckered conformation dihedral angles commonly range from 145 to 160" and there are positions analogous to the equatorial and axial positions of cyclohexane; in the planar conformation all positions are equivalent.,' The disodium salt of trans-1,3-cyclobutanedicarboxylicacid crystallises with two neutral acid molecules of crystahation Na,+C4H,(C0,),,2C4H,(C0,H), and the surprising result of an X-ray is that the neutral acid molecule which has a planar centrosymmetric ring when crystallized by itself,,* has a puckered ring with dihedral angle 155" while the dianion occupies a centre of 65 J.Eraker and C. Rsmming Actu Chem. Scad. 1967,21,2721. 66 H. Dietrich and H. Dierks Angew. Chem. 1968,80,487. 67 E. Adman and T. N. Margulis J. Amer. Chem SOC. 1968,90,4517. T. N. Margulis and M. S. Fischer J. Amer. Chem. SOC 1967,89,223. 50 George Ferguson symmetry and is therefore planar. The C-C single-bonds in the dianion average 1-563(9) A while those of the di-acid average 1.552(9) A. Tetra~yano-~' and octahydroxy-cyclobutane70molecules lie on symmetry centres in their crystals and are planar. The tetracyano-derivative is the cis-trans-cis isomer with ring bond-lengths 1.561(3) and 1.547(3) A the longer bond being between the atoms with a czs-arrangement of cyano-groups.In the octahydroxy- derivative the mean C-C bond-length is 1-562(4) A. The dihedral angles of the strained cyclobutane derivative (13) are 120" and the C-C-C angles are 87" at the bridgeheads and 75" at the other two carbon The conformations of the three cis-1,2-dihalogenobenzocyclobutenes(14) (X = C1 Br or I) are essentially similar with the cyclobutene ring planar rather than skewed and coplanar with the benzene ring plane within l.S".72 The brominated photo- dimer of 1,4-naphthoquinone 1,2,3,4-tetrabromo-1,2,3,4-diphthaloylcyclo-butane (15) has the anti-conformation in the solid state. A crystallographic two-fold axis coincides with the molecular two-fold axis (through the mid- points of the bonds linking the two halves of the molecule) and the cyclobutane ring is puckered.73 In the solid state 4,4-diphenylcyclohexanoneadopts a chair conformation in which the carbonyl end of the molecule is severely flattened ;74 the angle be- tween the planes C(2)C(l)C(6) and C(3)C(4)C(5) is 14" (in undistorted cyclo- hexane it is zero).The six-membered ring of cyclohexane-1,4-dione dioxime has the 'twisted boat' conformation and the molecule has nearly two-fold sym- metr~.~ Moleculesof 2,3-bis-( cis-4-chloro- l-methylcyclohexyl)-trans-but-2-ene (16) in the crystalline state present a case of intramolecular conformational isomerism in as much as the two cyclohexane rings exhibit chair conformations of opposite type in one ring the chlorine is equatorial whilst in the other it is axial.G (17) Me 2 69 B. Greenberg and B. Post Acta Cryst. 1968,24 B 918. 'O C. M. Bock J. Amer. Chem. Soc. 1968,90,2748. " A. Padwa E. Shefter and E. Alexander J. Amer. Chem. Soc. 1968,90,3717. '' G. L. Hardgrove L. K. Templeton and D. H. Templeton J. Phys. Chem. 1968,72,668. 73 G.J. Kruger and J. C. A. Boeyens J. Phys. Chem. 1968,72,2120. 74 J. B. Lambert R. E. Carhart P. W. R. Corfield and J. H. Enemark Chem. Comm. 1968,999. 75 P. Groth Actu Chem. Scud. 1968,22 128. 76 D. Mootz Acta Cryst. 1968 24 B 839. 51 X-Ray Crystallography c1 c1 R' Br :() 4 R2 (20) (21) In racemic crystals of geijereneesilver nitrate CI2H,8r 2AgN0 (17) the cyclohexene ring has a half-chair conformation with one carbon atom on each side of the planar four carbon (CHR-CH=CH-CH2) segment.The iso- propyl group is not planar and is trans to the vinyl group. Both groups associate with the same silver atom; another silver atom is associated with the cyclo- hexene double bond.77 The polyene canthaxanthin 4,4'-diketo-P-carotene (18),has a crystallographic centre of symmetry at the middle of the C(15)-C( 15') double-bond and the all-trans configuration of the conjugated bond system is interrupted at the cyclohexenone rings. The dihedral angles between the planes of the rings and the chains are 43" from s-ci.~.~~ When the central double-bond in (18) is converted to a triple bond to give 15,15'-dehydrocanthaxanthin,with the exception of the approximate s-cis orientation about the single bond from the chain to the cyclohexene rings the double-bond system again retains the all- trans configuration.The dihedral angle between the planes of the ring and chain is 28°.79 The eight-membered ring of trans-syn-trans-1,2,5,6-tetrabromocyclo-octane possesses a twisted crown conformation one of the predicted favoured con- formations for eight-membered rings. The C-C-C bond angles are all sig- nificantly greater than tetrahedral (mean value 118"). Results of dipole moment and n.m.r. investigations are in accord with the predominance in solution of one conformer and are compatible with this being the twisted crown found in the solid state." From a consideration of space-group symmetry requirements and unit-cell parameters it has been deduced'' that cis,cis-cyclo-3,8-diene-1,6-dione must possess a chair conformation (19) in the solid state.This is an example unfortunately all too rare in which useful information can be deduced without recourse to intensity measurements and extensive calculations. The conformation of 6-oxononanolide (oxycyclodeca-2,7-dione)82is similar to that observed in several cyclodecane derivatives' with the ring oxygen and carbonyl groups so situated as to minimise the number oftransannular H... H contacts. In " D. J. Robinson and C. H. L. Kennard Chem. Comm. 1968,914. 78 J. C. J. Bart and C. H. MacGillavry,Acta Cryst. 1968,24 B,1587. 79 J. C. J. Bart and C. H. MacGillavry,Acta Cryst. 1968,24 B 1569.G. Ferguson D. D. MacNicol W. E. Oberhansli,R. A. Raphael and J. A. Zabkiewicz Chem. Comm. 1968 103. H. L. Carrell B. W. Roberts J. Donohue and J. J. Vollmer J. Amer. Chem Soc. 1968,90,5263. 82 W. Fedeli and J. D. Dunitz Helv. Chim. Acta 1968 51,445. *' J. D. Dunitz and H. P. Weber Helo. Chirn. Acra 1964,47.951. and refs. therein. 52 George Ferguson large rings opportunities for transannular interaction are decreased and in cyclotetratriacontane [CH,] 34 the conformation is made up basically of two parallel zig-zag chains of 15 atoms linked at each end by two closure atoms conforming to a path traceable in the diamond lattice. Small twists and bond distortions occur in the side chains as a result of steric hindrance at the closure atoms.84 The pyrolytic reaction of perchloro-3,4-dimethylenecyclobutene gives at least four isomeric compounds of formula C12C11285 and yet another compound has been isolated from the reaction but this time with formula Cl2Cll4 (20).The molecule has two-fold crystallographic symmetry (the two-fold axis runs through the two ClC-CCl portions of the ring) and the cyclo-octatriene ring has a somewhat distorted tub conformation. Any two adjacent double-bonds out of the five do not lie in a plane and hence there will be no strong conjugation between them.86 Five isomerides of perhydroanthra-cene have been predicted two of which can be centrosymmetric. The isomer of m.p. 121"c is one of these and the configuration is cis-cis as referred to the single hydrogen atoms on the central ring.87 The mean value of the C-C-C bond angle is 111.5(2)".Two derivatives of bicyclo[2,2,2]octane (21) have been examined in an attempt to determine the preferred conformation of this system (crystals of the parent molecule are disordered). In the derivative (21; R' = p-BrC6H,-S02*CH2,R2= H)88 the carbon skeleton conforms to D symmetry with the group of atoms C(2)C(7)C(6) rotated 3" about the C(l) to C(4) axis with respect to the C(3)C(S)C(S) group. This has the effect of increasing the torsional angles at the C(2)-C(3) type bonds to 5" whereas with an eclipsed D, model a zero value would hold. In the disubstituted derivative (21; R' =R2 = C02H),89 however a non-twisted carbon skeleton with D, symmetry is found. 1-Bromotriptycene (22) has three-fold symmetry but there is also probably some disorder in its crystals.The C-Br distance is 1.97 A and the bridging C-C bonds have length 1.53 A at the bromine end and 1.51 A at the hydrogen indicating no conjugation between the aromatic rings." Ph. CO I (23) 84 H. F. Kay and B. A. Newman Acta Cryst. 1968,24 B 615. A. Furusaki Bull. Chem. SOC. Japan 1967,40,2518. 86 A. Furusaki and I. Nitta Tetrahedron Letters 1968 1379. 87 K. E. Hjortaas Acta Chem. Scad. 1967,21,2261. A. F. Cameron G. Ferguson and D. G. Morns Chem. Comm. 1968 316; J. Chem. SOC. (B) 1968,1249. 89 0.Ermer and J. D. Dunitz Chem. Comm. 1968,567. 90 K. J. Palmer and D. H. Templeton Acta Cryst.. 1968,24 B. 1048. X-Ray Crystallography 53 Whereas simple bicyclo[3,3,l]nonanes lacking substituents at positions 3 and 7 adopt flattened twin-chair conformations the derivative (23) is an example with a boat-chair conformation ;the distortion from ideal cyclohexane geometry is less than that in the twin-chair bicycl0[3,3,l]nonanes.~~The tri- cyclo[5,3,1,12~ 6]dodecane derivative (24) adopts a distorted double-chair conformation in spite of the exo-hydroxy-group at C( 12); however the hydroxy- hydrogen is held well clear of the methylene hydrogen at C(11) by an inter- molecular O-H...0bond to the carbonyl oxygen ofaneighbouring molecule.92 A short note9 andaf~llpaper~~ on the structure ofbullvalene(25) have appeared but a& by different research groups. In contrast to its behaviour in solution bullvalene shows no valence-isomerization in the solid state.Mean molecular dimensions from the full report94 are C-C(cyc1opropane) 1.539(7) C(sp')- C(cyc1opropane) 1.452(7) C=C 1-3 19(7) and C(sp')-C(apex) 1*508(7)A. Structure (26) for the novel cage molecule 3,4,5-trichlorotetracyclo[4,4,0,03~ 9 049 *]decan-2-one has been confirmed and the stereochemistry at C(5) de- termined. The cyclobutane ring is planar but the cyclopentane rings are puckered with internal angles varying between 97 and 106". The two cyclohexane rings are in boat form with internal angles close to tetrahedral (108-111") except for those at C(2). C(3 C(7) and C(l0)which are close to Nitrogen- Sulphur- and Oxygen-containing Hetero-compounds and Sugars.- A refinement of the structure of "'-dinitroethylenediamine reveals that the C-N distance is normal [1.463(4)A] but the N-N distance is abnormally short [1.301(4)A].Strong dipole-dipole interactions are suggested as the predominant crystal binding force.96 Methylglyoxalbisguanylhydrazone NH -C(NH). NH.C(CH,).CH -N.NH-C(NH)*NH,. which has marked activity toward human acute myelocytic leukaemia has been studied by X-ray and neutron diffraction in the form of the dihydrochloride monohydrate C5H12N8,2HCl,H20.97 The results are in good agreement with respect to the parameters of the non-hydrogen atoms. The hydrogen atoms were located precisely by the neutron diffraction study and the average apparent C-H N-H and 0-H bond-lengths are 0.1 A longer than those found in the X-ray study.In the crystals the dipositive ion C5H14Ng+ is planar and has a com- pletely trans-configuration of the chain. Methanesulphonanilide C6H NH SO2 CH, is related to a series of compounds with blood-pressure control activity. The aminohydrogen clearly sticks out alone on one side of the phenyl ring while the methylsulphone group is on the opposite side of the plane. The amino-hydrogen ofthe monomer is thus readily available to a receptor molecule during biological action.98 91 C. Tamura and G. A. Sim J. Chem. SOC. (B),1968,1241. 92 G. Ferguson and W. D. K. Macrosson J. Chem. SOC.(B) 1968,242. "S. M. Johnson J. S. McKechnie B. T.-S. Lin and I. C. Paul J. Amer. Chem Soc. 1967 89 7123. 94 k Amit R. Huber and W. Hoppe Acta Cryst. 1968,24 B 865. 95 D.Schwarzenbach Actu Cryst. 1968,24 B 238. 96 J. W. Turley Actu Cryst. 1968,24 B 942. 97 W. C. Hamilton and S. J. La Placa Actu Cryst. 1968,24 B 1147. 98 H P.Klug Actu Cryst. 1968 24 B,792. George Ferguson Intermolecular distances N...C2-98 and N...S 3.22 A in crystals of tetra-cyanothiophen suggests weak donor-acceptor bonding between the mole- cule~.~~ The paper also gives a reference list of bond lengths and angles reported in various thiophen derivatives. The structures of three isomeric dithienyls C8HhS2and of P-thiophenic acid have been examined. 2,2'-Dithionyl (27) 0 II c1 (28) decomposes in the X-ray beam while 2,3'- and 3,3'-dithienyl and P-thiophenic acid (28) are disordered with the sulphur atom effectively occupying two sites because of rotation of the thionyl groups about the exocyclic C-C bond.'OO This situation is not at all uncommon with molecules of this type.Dibenzo- thiophen sulphone (29) has two-fold (crystallographic) symmetry and conforms closely to Czvsymmetry experimentally the C-S-C and 0-S-0 angles are 92 and 120" respectively. lo' 2,2'-Dichlorotrimethylenesulphite has con- formation (30) with the S=O group axial and the molecule has C,symmetry within the limits of error.Io2 Thiepin 1,l-dioxide exists in the flattened boat- conformation (31). The C(p)-C(y) type bonds are abnormally short (1.429 (31) 99 V. Rychnovsky and D. Britton Acta Cryst. 1968,24 B 725. loo G. J. Visser G. J. Heeres J. Wolters and A. Vos Acta Cryst. 1968 24 B 467. lo' L.R. Kronfeld and R. L. Sass Acta Cryst. 1968,24 B 981. lo2 J. W. L. van Oyen R. C. D. E. Hasekamp. G. C. Verschoor and C. Romers Acta Cryst. 1968 24 B 1471. 55 X-Ray Crystallography Me Me (35) 1.438 A),as are the C-S bonds (1-723,1.716 A) and suggest that some unusual bonding effects are being observed resulting in a flattening of the hydrocarbon portion of the ring. In agreement with this the internal bond-angles are some- what enlarged (C-%-C values range from 122-8-129.4" and C-C is 103.3°).103 The meso-ionic structure is found for the thiabenzene derivative (32)and the C-H adjacent to the sulphur atom is involved in an intermolecular hydrogen bond,C-H.-O=C /of3~12~.104Thefirstcrystal-structureanalysis \ of a bithiazole ring system shows that the molecule (33) is nearly ~1anar.l'~ The structure of the antibiotic anisomycin has been determined from an analysis of a N-acetylbromo-derivative.The molecule is the substituted pyrroli- dine (34) and an analysis of stereoelectronic factors governing ring-opening reactions of cyclopentane derivatives is also presented.Io6 The calcium salt of 2,6-pyridinedicarboxylicacid is found as the tri- and sesqui-hydrate. The crystal structure of the trihydrate (a bacterial spore metabolite) is built up of planar calcium dipicolinate dimers linked by water molecules. One of the hydrogen atoms of the pyridine ring forms a hydrogen bond to the carbonyl group of another dipicolinate ion [CH-..O 3-15(1) A],linking the ions into an infinite 103 H.L. Ammon P. H. Watts jun. J. M. Stewart and W. L. Mock J. Amer. Chem. SOC.,1968,90. 4501. Io4 C. Tamura S. Sato and Y. Kishida Tetrahedron Letters 1968 2739. G. Koyama H. Nakamura Y. Muraoka T. Takita K. Maeda H. Umezawa and Y. Iitaka. Tetrahedron Letters 1968,4635. J. P. Schaefer and P. J. Wheatley J. Org. Chem. 1968,33 166. George Ferguson ribbon by a ten-membered centrosymmetric ring with sequence ~H.-occcH.-oC~.~~~ Two structures (35)'" and (36),lo9 which are stable nitroxide radicals have been reported. The NLO bond-lengths are 1.26(4) and 1.31(2) A in (35) and (36) respectively and in both molecules the angles which the NIO bond makes with the C-N-C plane are comparable (21 and 24" respectively). In the tri-p- nitrophenylmethyl free-radical the C-C bond-lengths at the central carbon atom are 1.47(4) A.110 Ph Ph"3ph (37) (38) ph (39) 0I R (40) (41) (42) 'CI H (431 (44) (45 1 Interesting features of (37) include an intramolecular C-H ...N hydrogen bond (H...N is 2.15 and C.-.N 2-91 A) and a C-C-N angle of 81" within the four-membered ring.' l1 The pyrazoline ring in (38) is non-planar and N-N is 1.336 and N=C 1.333(7%; the dihedral angle between the planes of the phenyl rings is 1l0.ll2 The imidazoline ring of the hydrobromide of (39) is also sig- nificantly non-planar with C(17) lying 0.15 A out of the plane of the other four atoms.' 1,3-Diazepine-2-thione has conformation (40) with valency angles of 117" at the methylene carbon atoms and 131" at the nitrogen atoms; the lo' G.Strahs and R E. Dickerson Acta Cryst. 1968,24 B 571. Io8 J. LajzCrowicz-Bonneteau,Acta Cryst. 1968,24 B 196. Io9 D. M. Hawley G. Ferguson and J. M. Robertson J. Chem SOC.(B),1968,1253. P. Andersen and B. Klewe Acta Chem Scad. 1967,21 2599. 111 C. J. Fritchie jun. and J. L. Wells Chem. Comm. 1968,917. B. Duffin Acta Cryst. 1968 24 B,1256. J. S. McKechnie and I. C. Paul J. Chem. SOC.(B),1968.984. X-Ray Crystallography 57 dihedral angle between the [CH,] group and the CH,NNCH group is 127".l14A study of 1H-azepine in the free (41; R = SO2C6H4Br) and com- plexed (41; with Fe(CO) and R = C0,Me) state reveals that the free form and presumably closely related 1H-azepines are true polyenes.' ' The anti- biotic myxin has been confirmed as 1-hydroxy-6-methoxyphenazine5,lO-dioxide by a very precise analysis at -160"~~~~ A combination of bond- stretching and angle-bending is found in the overcrowded region of o-di-t-butylquinoxaline (42); the C(2)-C(3) bond is 1-475(6) A and angles of type C(2)-C(3)-C(15) are 130".'l7 In a paper on quaternisation reactions Lund and Gruhn describe a compound to which they ascribe formula (43) and this has been confirmed by X-ray analysis which reveals that the molecule is nearly planar.l1 A tetrazolopurine prepared from 6-hydrazinopurine by treatment with HNO has been shown to be (44),which is planar and packs with other molecules in planes 3-35 A apart. There is a close intermolecular C-H-a-N packing distance between molecules with C-..N 3.23 and H.-N 2-19 There are significant and symmetrical in-plane distortions of the benzene ring in saccharin o-6,H4SO2NH -CO and strain in the five-membered ring results in large angular distortions.The molecules are held in the crystal by strong N-H.-.O hydrogen-bonds 2.79 A.12o Dihydrouracil12' and dihydrothymine122 adopt half-chair conformations with the hydrogenated carbon atoms 0.3 to 0.35A out of the plane of the other ring atoms. In dihydrothymine the methyl group is equatorial. Both uracil and dimethylthymine dimers can be isolated from irradiated frozen solutions of the appropriate monomer. In the cis-syn-isomer of uracil (45)' 23 the cyclobutane ring has a dihedral angle of 155" and the heterocyclic rings are also not planar. Atoms C(5)and C(6) in each ring are -0.13 and +0-15A out of the ring plane and the rings are in addition twisted relative to one another by 24".Essentially the same type of structure is obtained on irradiation of dimethylthymine; the cyclobutane ring is markedly puckered (each carbon atom being 0.6 A out of the plane of the other three) and the two thymine residues are rotated relative to each other by 28G.124 Preliminary details of the structures of the 3',5'-cyclic phosphates of adenosine'25 and uridine' 26 have been given. M. Mammi A. del Pra and C. di Bello Ricerca sci. 1967,37 766. I. C. Paul S. M. Johnson L. A. Paquette,J. H. Barrett and R J. Haluska J. Amer. Chem Soc. 1968,90,5023. A. W. Hanson Acta Cryst. 1968,24 B,1084. G. J. Visser A. Vos A.de Groot and H. Wynberg J. Amer. Chem. SOC.,1968,90,3253. M. S. Lehmann and S. E. Rasmussen Acta Chem. Scad. 1968,22 1297. J. P. Glusker D. van der Helm W. E. Love J. A. Minkin and A. L. Patterson Acta Cryst. 1968,24,B,359;cf ref 111. lz0 J. C. J. Bart J. Chem. SOC.(B),1968 376. 12' D.Rohrer and M. Sundaralingam Chem. Comm. 1968 746. 12' S.Furberg and L. H. Jensen J. Amer. Chem. SOC.,1968,90,470. 123 E.Adman h4. P. Gordon and L. H. Jensen Chem Comm. 1968 1019. N.Camerman and A. Camerman Science 1968,160 1451. 125 K.Watenpaugh J. Dcw L. H. Jensen and S. Furberg Science 1968 159,206. lZ6 C.L.Coulter,Science 1968 159 888. George Ferguson The dimensions of the peroxide bond in various organic molecules including 4,4'-dibromo- and 4,4'-dichlorodibenzoyl peroxide have been compared.Six independent determinations of the peroxide bond-length have a mean value 1-47A. The peroxide dihedral angle by contrast appears strongly dependent upon its environment and values from 81 to 139" have been As part of a study of the geometry of cyclic organic peroxides the structures of (46),128 Y OH OH 0 -CH OH I OH OMe (49) (50) and (47; n = 5-7),12' have been described. The 0-0 distances lie between 1-47 and 1-48 A. In(47) the environment of the spiro-carbon atoms is asymmetric probably caused by intramolecular repulsion between hydrogen and oxygen atoms. In (47; n = 6)130 the cycloheptylidene rings have the chair form w mean C-C-C angle 115-3" while in (47; n = 7)131 the cyclo-octylidene ri conformation corresponds to 'boat-chair' and the average C-C-C angle is 116.5".The carboxy-groups in furan-a,a'-dicarboxylic acid are twisted 4" out of the furan-ring plane.132 The structure of a compound C12H200,derived from methoxyacetylene has been determined as the dioxa-admantane (48). The molecule has a two-fold crystallographic axis through the 0x3-oxygen atoms and the geometry of the skeleton is very similar to that of adamantane.133 L-Ascorbic acid 'vitamin C' (49) has been investigated by X-ray134 and neutron135 diffraction. The enediol group is planar and the average C-0-H 12' S. Caticha-Ellisand S. C. Abrahams Acta Cryst. 1968 24 B 277. P' Groth Acta Chem. Scad. 1967,21,2711. 129 P. Groth Acta Chem. Scad. 1967,21,2608.P. Groth Acta Chem. Scad. 1967,21,2631. 13' P. Groth Acta Chem. Scad. 1967,21,2695. E. Martuscelli and C. Pedone Acta Cryst. 1968,24 B 175. J. A. Kanters and J. B. Hulscher Rec. Trav. chim. 1968,87,201. 134 J. Hvoslef Acta Cryst. 1968 24 B 23. J. Hvoslef Acta Cryst. 1968,24 B 1431. X-Ra y Crystallography 59 angle in it is 113-9" while the alcohol C-0-H angle is 109.2"; the average C-C-H and 0-C-H angle is also 109.2". Molecules of DL-arabinitol C,H,(OH),136 and galactitol C,H,(OH),13' have planar zig-zag carbon chains with oxygen atoms above and below the plane; all oxygen atoms are involved in hydrogen bonding. The A'-and B- forms of D-mannitol have essen- tially the same conformation in their crystals with approximate two-fold symmetry and a planar carbon chain.The dimorphism is due to different systems of hydrogen bonding.' ''Another form of D-mannitol labelled K was obtained accidentally and it transpires that it has the same conformation as the B-form with a carbon chain planar to within 0.09 8 and a two-fold axis within 0.01 The B-and K-polymorphs have similar system of hydrogen bonds in different steric arrangements. The crystal structures of P-D-glucose and of cello- biose have been refined with new data.'40 The equatorial glycosidic C(l)-O(l) bonds are significantly short [1.383(4) and 1-397(4) 8 respectively] in agreement with observations in other sy~terns.'~' Methyl a-D-glucopyranoside is in the trans-C(1) chair-conformation. The C(1)-0( 1) bond 1.41 l(4) A is slightly shortened and there is a significant difference between C-0 bonds in the pyranose ring[C(1)-0(5) 1.414; 0(5)-C(5) 1.434(4) 8,].'" The absolute configuration of methyl-4,6-dichloro-4,6-dideoxy-a-~-glucopyranoside has been determined as (50);the molecule is in the normal chair-conf~rmation.'~~ Molecular Complexes.-In crystals of NNN'W-tetramethyl-p-diaminoben-zene iodide [tmpd] -t I-the cation has crystallographic 2/m ~yrnrnetry'~~ and in the bromide of the NN-dimethyl derivative [dmpd] 'Br- m ~yrnrnetry'~ is demanded for the cation.In both cations there is considerable quinonoid character as judged by the bond lengths. The 1:2 complex of tmpd with 7,7,8,8-tetracyanoquinodimethane[tcnq]; [tmpd] consists of columns of + tmq ions which overlap in characteristic fashion and are held together by hpd ions.The average spacing between tcnq ions is 3.24 Similarly in e 2 1 complex oftcnq with tetraphenylphosphonium ion [tpp]+[t~nq],,'~' dimer pairs of tcnq ions are found about an inversion centre sharing a single negative charge and overlapping in characteristic fashion. There is good agreement between the analyses on the geometry of the (tcnq))- ion and the distances are intermediate between these of (tcnq)" and (tcnq)-'. The mean perpendicular separation of the molecules in the 1 1 complex tcnq :anthracene is 3-50 A and in conjunction with the structural geometry implies only weak 136 F. D. Hunter and R. D. Rosenstein Acta Cryst. 1968,24 B 1652. 13' H. M. Berman and R. D. Rosenstein Acta Cryst.1968,24 B 435. 13* H. M. Berman G..A. Jeffrey and R. D. Rosenstein Acta Cryst. 1968,24 B 442. 139 H. S. Kim G. A. Jeffrey andR. D. Rosenstein Acta Cryst. 1968,24 B 1449. S. S. C. Chu and G. A. Jeffrey Acta Cryst. 1968,24 B 830. 141 S. S. C. Chu and G. A. Jeffrey Acta Cryst. 1967,23 1028. H. M. Berman and S. H. Kim Acta Cryst. 1968,24 B 897. 143 R. Hoge and J. Trotter J.Chem. SOC. (A) 1968,267. 144 J. L. de Boer A. Vos and K. Hume Acta Cryst. 1968,24 B 542. 14' J. Tanaka and N. Sakabe Acta Cryst. 1968,24 B 1345. 146 A. W. Hanson Acta Cryst. 1968,24 B 768. 14' P. Goldstein K. Seff and K. N. Trueblood Acta Cryst. 24 B 778. 60 George Ferguson charge-transfer interaction betwen molecules. The central six-membered rings of the two types of molecule are oriented at 30" to one another to ensure maximum 0ver1ap.l~~ Each molecule in the tmpd:chloranil complex lies in a mirror plane has symmetry 2/m and the short distance between the rings (b/2 = 3.284 A)indicates a strong intermolecular intera~ti0n.l~~ There is a mean separation of 3.32 A between the molecular planes in the pyrene :tetracyano-ethylene and some of the bond lengths in the pyrene molecule differ by 0.1 A from these found in the pyrene :tetramethyluric acid complex.' ' The structures of quinhydrone C6H402,C6H4(OH)2 and phenoquinone C6H,02,2C6H,0H have been refined.' 52 A striking example of virtually identical packing of molecules in a one-component crystal and in one of its addition compounds is provided by tetrabromoethylene and its 1 :1 pyrazine adduct.Similar but not identical behaviour is found in the tetraiodoethylene pyrazine system.' The 1:1 complex of 5-bromouridine and dimethylsul- phoxide (dmso) has hydrogen bonds between the DMSO oxygen and two hydroxyl-groups of the 5-bromouridine molecules. A comparison is made between the 5-bromouridine molecule in this structure and those found in two other related ~tructures.'~~ Natural Products.-The determination of the structure of a p-bromobenzoyl- urethane derivative of dihydrofomannosin establishes the structure of foman- nosin a biologically active metabolite of the fungus Fumes annosus. The deriva- tive (51) contains a puckered cyclobutane ring with a dihedral angle of 22" (158') and a cyclopentanone ring in an envelope conformation.' 55 Structure (52)has been determined for humulene bromohydrin; thus during its formation attack on the 1,2 double-bond in humulene is cis.The eight-membered ring has boat-chair conformation distorted from m symmetry by the ring fusion ; the mean C-C-C angle in the ring is 117-4(6)". The cyclobutane ring has a dihedral angle of 151" and the geometry of cyclobutane and cyclo-octane rings in a number of molecules is discussed.' 56 Caryophyllene 'iodonitrosite' a stable nitroxide radical has structure (36). The four-membered ring is buckled (dihedral angle 145") and the seven- and six-membered rings have chair conformations but with enlarged C-C-C angles because of intramolecular overcrowding effects.lo9 Structure (53) has been assigned to the 2-bromo- derivative of lumisantonin a photo-irradiation product of a-santonin.The configuration at the asymmetric carbon atoms confirms the now accepted stereochemistry of cc-santonin.' 57 148 R. M. Williams and S. C. Wallwork. Acta Cryst.. 1968. 24. B. 168. 149 J. L. de Boer and A. Vos Acta Cryst. 1968,24 B 720. 150 I. Ikemoto and H. Kuroda Acta Cryst. 1968,24 B 383. 15' A. Damiani P. de Santis E. Giglio A. M. Liquori R. Puliti and A. Ripamonti Acta Cryst. 1965,19 340. 152 T. Sakurai Acta Cryst. 1968,24 B 403. 153 T. D. Ah1 and 0.Hassel Acta Chem. Scad. 1968,22 715. 154 J. Iball C. H. Morgan and H. R Wilson Proc. Roy. Soc. 1968 A 302 225. 155 A. T. McPhail and G. A. Sim J. Chem. Soc. (B) 1968,1104. F. H. Allen and D. Rogers J.Chern. SOC.(B),1968,1047. 15' C P Huber and K. J Watson. J Chem. Soc (CI. 1968. 2441. X-Ray Crystallography Isoeremolactone has structure (54). Some of the C--C bonds are longer than expected and are associated with a high degree of substitution at these atoms ;similarly the bond angles at these atoms also differ from tetrahedral."' Details of the crystal structures of P-bromopicrotoxinin'59 and phorbol bromo- furoate'6o have been reported and preliminary details of the structures of OAc 15' Y. L. Oh and E. N. Maslen Acta Cryst,24 B 883. ls9 B. Jersley E. J. Rayn-Jonsen and J. Danielsen Acta Cryst. 1968 1968,24 B,1156. I6O R. C. Pettersen G. I. Birnbaum G. Ferguson K. M. S.Islam and J. G. Sime,J. Chem. SOC.(B) 1968.980. 62 George Ferguson eunicellin a diterpenoid of the gorgonian Eunicella stricta16' and ryanodol from Ryania speciosa Vahl,' 62 have been published.The configuration at C(13) in labdanolic and eperuic acids has been established as (S) (Prelog's notation) by an analysis of a p-bromophenacyl ester of labdanolic acid.'63 A considerable number of crystallographic papers have dealt with steroid structures in the past year. One of the most discusses the geometry and conformation of ring D in a number of steroids and some empirical rules that may serve as a basis for discussion of ring D conformation are recognised. To a first approximation the nature of the C(17) or C(16) P-substituent (except keto) has no discernible influence and extreme deformations of rings A B and/or c do not affect ring D.(A quantitative description of the conformation of the A B and c rings in steroids was published earlier.'65) Full details of the crystal and molecular structures of the steroid derivatives 3P-acetoxy-17a- hydroxy-16~-brorno-5~t-pregnan-l1,20-dione,'~~2l-bromo-3P 17a-dihy- . dro~y-5a-pregnan-ll,20-dione,'~~and 12a-bromo-l lP-hydroxyprog-esterone'68 have been published and also of the 2 1 complex of testosterone and mercuric ~hloride,'~' 3~,6~-dimethoxy-5~,19-cycloandrostan-17-one N-acetyl-p-brosylhydrazone,' o 9a-bromo- 17 P-hydrox y-17a-methylandrost-4-ene-3,l l-dione,17 fusidic acid methyl ester 3-p-brornoben~oate,'~~ withaferin A acetate p-bromobenzoate (55),' 73 and 3-methoxy-5~,19-cyclo-5,l0-seco-androsta-l( 10),-2,4-trien-17P-y1 p-bromobenzoate (56) which has ring A in a tub conf~rmation.'~~ The unusual structure (57) results from the benzilic acid rearrangement of 3a,l7P-diacetoxy- 1 1 -hydroxy-12-oxo-5P-androst-9( 1 1)-ene ; severe steric compression results from the cis fusion of the three five-membered rings.'75 Preliminary details have been announced of the structures of 8,13- diaza-18-noroestrone methyl ether,'76 the principal aglycon of horse chestnut saponin (58),177 the p-bromobenzoate of 6-oxoleucotylin (59),'78 and hirun- digen and anhydrohirundigen two natural 15-0xasteroids.'~~ 16' 0.Kennard D.G. Watson L. Riva di Sanseverino B. Tursch R Bosmans and C. Djerassi Tetrahedron Letters 1968,2879. 16' S. N. Srivastava and M. Przybylska Canad.J. Chem. 1968,46 795. 163 K. Bjamer G. Ferguson and R. D. Melville Acta Cryst. 1968,24 B 855. 164 C. Altona H. J. Geise and C. Romers Tetrahedron 1968,24 13. H. J. Geise C. Altona and C. Romers Tetrahedron 1967,23 439. 166 J. M. Ohrt B. A. Haner A. Cooper and D. A. Norton Acta Cryst. 1968,24 B 312. 167 J. M. Ohrt A. Cooper G. Kartha and D. A. Norton Acta Cryst. 1968 24 B 824. A. Cooper and D. A. Norton Acta Cryst. 1968,24 B 811. A. Cooper E. M. Gopalakrishna and D. A. Norton Acta Cryst. 1968,24 B 935. 170 C. Tamura and G. A. Sim J. Chem. SOC.(B),1968 8. 17' A. Cooper C. T. Lu and D. A. Norton J. Chern. SOC. (B),1968 1228. 17' A. Cooper and D. C. Hodgkin Tetrahedron 1968,24,909. 173 A. T. McPhail and G. A. Sim J. Chem. SOC.(B),1968,962. H. Hope and A.T. Christensen Acta Cryst. 1968 24 B 375. 175 J. S. McKechnie and I. C. Paul J. Amer. Chem. Soc. 1968,90 2144. 176 J. H. Burckhalter H. N. Abramson J. G. MacConnell R J. Thill A. J. Olson J. C. Hanson and C. E. Nordman Chem. Comm. 1968 1274. "' W. Hoppe A. Gieren N. Brodherr R Tsechesche and G. Wulff Angew. Chem. 1968,80 563. T. Nakanishi T. Fujiwara and K. Tomita Tetrahedron Letters 1968,1491. 17' 0.Kennard J. K. Fawcett D. G. Watson K. A. Kerr K. Stockel,W. Stocklin and T. Reich-stein Tetrahedron Letters 1968 3799. X-Ray Crystallography Precise details of the molecular geometry of the alkaloid reserpine (60)have been reported.18' The structure was solved by a combination of the symbolic (60) addition procedure for non-centrosymmetric space groups,' 81 a recycling procedure,ls2 and use of the tangent formula.'83 The authors note that 'the facility with which the structure was obtained for this molecule possessing 44 atoms exclusive of hydrogens and without a heavy atom indicates that the limit of the method has not been reached' ! In reserpine the trimethoxybenzoxy- group is nearly perpendicular to the remainder of the molecule and steric effects prevent all three methoxy-groups being in or near the plane of the benzene ring.The indole group is planar and only C(7)and N(8) are out of the plane in the adjacent ring. The next two rings are in chair conformation. Atom N(8) is pyramidal with bond angles near 111". Structure (61) has been determined for the alkaloid haloxine. Although this is a natural product with asymmetric carbon atoms its hydrobromide crystallises in a centrosymmetric space group so that it must be racemic.The three six-membered rings are in chair conforma- tion.la4 The structure of acutumine (62) an alkaloid containing chlorine is I. L. Karle and J. Karle Acta Cryst. 1968 24 B 81. la' J. Karle and I. L. Karle Acta Cryst. 1966 21 849. J. Karle Acta Cryst. 1968,24 B 182. la3 J. Karle and H. Hauptman Acta Cryst. 1956,9 635. lB4B. Nilsson Acta Cryst. 1968 24. B 252. George Ferguson Me0 Me0 (61) OMe OMe HO 0 HO closely related to that of hasubanonine but has a spiran-type juncture of two five- membered rings. Ring A is planar but the other two five-membered rings are puckered and the six-membered ring is in the boat conformation.' The structure and absolute configuration of coclaurine have been determined as (63). The (+)-enantiomer has D-configuration and the chirality of the molecular structure is correlated with circular dichroism measurements.' 86 The ten-membered ring in bothprotopine(64;R' = R2 = CH2)187andcryptopine(64;R'= R2 = Me)188 is severely buckled with the nitrogen atom well buried within it and held very close to the carbonyl carbon atom C(14); N-sC(14) is only 2-57(1) A. The three C-N bonds and the N..-C(14) 'bond' across the ring are nearly tetrahedrally arranged around the nitrogen atom. Consequently in the formation of a deriva- tive with tetravalent nitrogen inversion at the nitrogen atom would be required unless the fourth bond formed was N-C( 14).Alkaloid derivatives which have been the subject of preliminary communications include sparteine N( 16)-oxide [ions of which are held in the crystal by a short symmetrical O...H*-O lS5 M. Nishikawa K. Kamiya M. Tomita Y. Okamato T. Kikuchi K. Osaki Y. Tomiie I. Nitta and K. Goto J. Chem SOC.(B) 1968,652. ls6 J. Fridrichsons and A. McL. Mathieson Tetrahedron 1968,24 5785. lS7 S. R Hall and F. R Ahmed Acta Cryst. 1968 24 B 337. ''* S. R. Hall and F. R. Ahmed Acta Cryst. 1968 24 B 346. X-Ray Crystallography hydrogen bond 2.479(8)A],' 89 daphmacrine,' coulteropine,' 9' kreysiginine and morphine,lg2 vallesamidine,' 93 capaurimine and capaurine,lg4 (-)-kopsanone,l 95 oxotuberostemonine,' 96 batrachotoxinin A a novel steroid alkaloid from the Colombian poison-arrow frog,' 97 and beratrobasine.' 98 Duclauxin one of the metabolites of PeniciIIium Duclauxi Delacroix has been established as (65; R = H) by an analysis of a monobromo-derivative (65; R = Br).It consists of two nearly planar rings one containing an iso- coumarin and the other a dihydroisocoumarin nucleus ;these are joined through the five-membered ring to form a hinge-like structure.lg9 The structure and absolute configuration of the fungus metabolite ophiobolin has been established as (66). The derivative used was the methoxybromide.200 This structure is closely related to those of ceroplasteric acid (67; R = C02H) and ceroplastol I (67; R = CH,*OH). whose structure have also been determined by X-ray methods.'* lS9 S.N. Srivastava and M. Przybylska Tetrahedron Letters 1968 2697. T. Nakano Y. Saeki C. S. Gibbons and J. Trotter Chem. Comm. 1968,600. 19' F. R Stermitz R M. Coomes and D. R. Harris Tetrahedron Letters 1968. 3915. 19' J. Fridrichsons M. F. Mackay and A. McL. Mathieson Tetrahedron Letters 1968 2887. 193 S. H. Brown C. Djerassi and P. G. Simpson J. Amer. Chem. SOC.,1968,90 2445. 194 T. Kametani M. Ihara K. Fukumoto H. Yagi H. Shimanouchi and Y. Sasada Tetrahedron Letters 1968 4251. 19' B. M. Craven B. Gilbert and L. A. P. Leme Chem. Comm. 1968,955. 196 C. P. Huber S. R Hall and E. N. Maslen Tetrahedron Letters 1968,4081. 19' T. Tokuyama J. Daly B. Witkop I. L. Karle and J. Karle J. Amer. Chem. SOC. 1968 90 1917. 19* G. N. Reeke jun.R L. Vincent and W. N. Lipscomb J. Amer. Chem. SOC. 1968,90 1663. 199 Y. Ogihara Y.Iitaka and S. Shibata Acta Cryst. 1968,24 B 1037. 'O0 M. Morisaki S. Nozoe and Y. Iitaka Acta Cryst. 1968 24 B 1293. 201 Y. Iitaka I. Watanabe I. T. Harrison and S. Harrison J. Amer. Chem. Soc. 1968,90 1092. George Ferguson Vanadyl deoxophylloerythroetioporphyrin,C,,H 34N4V0,(68),an analogue of chlorophyll has the shape of a very shallow saucer. The four nitrogens are coplanar with the vanadium atom 0-48A from this plane. The strain introduced by ring E is not localised but transmitted throughout the molecule :the four-fold symmetry characteristic of many porphyrins and porphines has vanished. Another effect of the E ring is that it appears to have ‘pushed’ the nitrogen atom of ring c in towards the vanadium as the V-N distance (1.97 A) is significantly shorter than the other three V-N distances (mean 2-11 A$).2o2 ’O’ R C.Pettersen and L. E. Alexander J. Amer. Chem SOC.,1968,90 3873.