Dieter Schwarzenbach

Observation of Uniaxial Negative Thermal Expansion in an Organic Crystal

Reference LCR-ARTICLE-2010-024doi:10.1002/1521-3773(20020301)41:5 3.0.CO;2-R Record created on 2010-01-13, modified on 2017-05-12

Statisical descriptions in crystallography. II. Report of a Working Group on Expression of Uncertainty in Measurement

The Working Group has examined recent recommendations for evaluating and expressing uncertainty in measurement [Guide to the Expression of Uncertainty in Measurement, International Organization for Standardization (ISO, 1993)]. The present publication updates an earlier report of the IUCr Subcommittee on Statistical Descriptors [Schwarzenbach, Abrahams, Flack, Gonschorek, Hahn, Huml, Marsh, Prince, Robertson, Rollett & Wilson (1989). Acta Cryst. A45, 63-75]. This new report presents the concepts of standard uncertainty, of combined standard uncertainty, and of Type A and Type B evaluations of standard uncertainties. It expands the earlier dictionary of statistical terms, recommends replacement of the term estimated standard deviation (e.s.d.) by standard uncertainty (s.u.) or by combined standard uncertainty (c.s.u.) in statements of the statistical uncertainties of data and results, and requests a complete description of the experimental and computational procedures used to obtain all results submitted to IUCr publications.

Iron, molybdenum and tungsten carbonyls of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe(CO)3

Abstract The reaction of 5, 6, 7, 8-tetrakis(methylene)bicyclo[2.2.2.]oct-2-ene (1) with Fe29CO)9 yields under various conditions the exo and endo-tetrahaptotri-carbonyliron complexes(2 and3) and the endo, exobis(tetrahaptotricarbonyliron) complex (4); with Fe(CO)39benzalacetone), 2 and the bis(exo-tetrahapto-tricarbonyliron) complex (5) are obtained. The little ligand reacts with M(CO)3(CH3CN)3 (M = Mo, W) giving respectively the hezahapto-tricarbonyl-molybdenum and -tugnsten complex (6, 7). Coordination of all five double bonds of the pentaene is achieved by reacting 2 with Mo9CO)3(CH3CN)3 giving the exo-tetrahapto-tricarbonyliron-hexahapto-tricarbonylmolybdenum complex (8). The structures of complexes 3–8 in solution were deduced from their NMR data and the molecular structure of 2 was determined by X-ray crystallography. The Fe(CO)3 group is in th eexo position with respect to the roof-shaped pentaene. The ligand is bound through one s-cis-butadiene group to two basal positions of a tetragonal pyramidal Fe(CO)3X2 moiety. Hydrogen atom positions were refined in the last cycles (final residual R = 0.023). H(Z) atoms deviate from the diene plane of the coordinated diene away from the metal by ∼42°, whereas H(E) atoms deviate towards the metal by ∼16°. Hybridization at the “inner” carbon atoms as well as at the carbon atoms of the other three double bonds does not differ significantly from sp2. Kinetic study of the cycloaddition reaction of a dienophile to the free 1, 3-diene system of the monometallic complexes shows that the rate with respect to that of the free ligand is not much affected by the presence of the metal.

Structure of C60: partial orientational order in the room-temperature modification of C60

Using published synchrotron X-ray data, the room-temperature scattering density distribution of pure C 60 has been parametrized in terms of a combination of eight oriented symmetry-related images of the molecule, and of a freely spinning molecule. Corresponding populations are 61 and 39%. The oriented part of the model is obtained, in good approximation, by imposing m3m symmetry on the energetically more favourable major orientation in the low-temperature structure of C 60

Stacking disorder: the hexagonal polymorph of tris(bicyclo[2.1.1]hexeno)benzene and related examples

Abstract X-ray diffractograms of tris(bicyclo[2.1.1]hexeno)benzene, crystallized at the interface between a benzene solution and a layer of acetonitrile, show hexagonal symmetry and streaks of diffuse scattering along c*. The heavily faulted layer stacking is analyzed qualitatively and quantitatively in terms of a systematic protocol. This protocol requires partitioning the crystal structure into layers in such a way that pairs of adjacent layers may be stacked in different, but geometrically equivalent ways, which are dictated by the layer group symmetry. This approach is shown to provide a consistent alternative for analysis of a number of related cases provided the layers are defined on the basis of geometrical criteria rather than chemical intuition.

Dithiophosphinate Complexes of the Actinides. II. Preparation and Characterisation of the Compounds UO2(S2PR2)2·R'OH, [Et4N][UO2(S2PR2)2Cl] and UO2(S2PR2)2·Me3PO. The Crystal Structures of UO2(S2PR2)2·EtOH, R = Ph and C6H11, [Et4N][UO2(S2PR2)2Cl], R = Me and Ph, and UO2(S2PMe2)2·Me3PO

Abstract Salts of dithiophosphinic acids, R 2 PS 2 H, react with UO 2 Cl 2 in alcoholic, R′OH, solution to yield the complexes UO 2 (S 2 PR 2 ) 2 · R′OH. In the presence of excess chloride ion the alcohol is displaced to form the anionic chloro-complexes, which may be isolated as their [Et 4 N] + salts. Similar reactions with UCl 4 in the air yield the same compounds in a novel double oxidation reaction. The initially formed U(IV) complexes are rapidly oxidised by the air to yield the corresponding uranyl compound and, at the same time, two ligands are oxidised to form the dimer, [R 2 PS 2 ] 2 . When [UCl 6 ] 2− is employed, only the chlorocomplexes are obtained. The complexes for R = Me, Et, Pr i , OMe, OEt, OPr i , Ph and C 6 H 11 have been characterised by elemental analysis, IR and NMR spectroscopy. From one reaction of UVl 4 and NaS 2 PMe 2 , the complex UO 2 (S 2 PMe 2 ) 2 · Me 3 PO was obtained by an unknown route. The crystal structures have been determined for two alcohol adducts, two chlorocomplexes and the phosphine oxide adduct. UO 2 (S 2 PPh 2 ) 2 · EtOH: Triclinic, a = 11.589(2), b = 11.6928(8), c = 13.273(2) A , α = 113.205(8), β = 110. 849(9), γ = 92.979(9)°, P 1 , R = 0.057. UO 2 {S 2 P(C 6 H 11 ) 2 } 2 · EtOH: Monoclinic, a = 12.765(1), b = 16.502(2), c = 15.813(2) A , β = 90.622(9)°, P2 1 /n, R = 0.044. [Et 4 N][UO 2 (S 2 PMe 2 ) 2 Cl]: Orthorhombic, a = 10.770(1), b = 11.730(2), c = 20.079(2) A , P2 1 2 1 2 1 , R = 0.033. [Et 4 N][UO 2 (S 2 PPh 2 ) 2 Cl]: Monoclinic, a = 11.341 (2), b = 20.889(30, c = 16.172(2) A , β = 101.79(1)°, P2 1 /n, R = 0.046. UO 2 (S 2 PMe 2 ) 2 · Me 3 PO: Orthorhombic, a = 11.499 910, b = 13.079(1), c = 14.362(1) A , Pcmn, R = 0.050. All five complexes have pentagonal bipyramidal structures. The pentagonal plane contains four sulphur atoms from the two bidentate dithiophosphinate ligands (US = 2.873 A ) and one oxygen or chlorine atom from the coordinated ethanol (US = 2.41 A ), phosphine oxide (US = 2.32 A ) or chloride (US = 2.677 A ). The uranyl group is linear (US = 1.76 A ) and perpendicular to the equatorial plane. In both ethanol adducts the ethyl groups of the alcohol are disordered. The phosphine oxide adduct has crystallographic m symmetry. No more than two bidentate ligands could be attached to the uranium; however, a fifth equatorial coordination site is always occupied by an additional ligan, even when the substituents at phosphorus are bulky.

Stereospecific functionalisations of iron carbonyl complexes of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe2(CO)6

Abstract When the reaction between an excess of Fe 2 (CO) 9 and the pentaene 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene(I) is carried out in hexane/methanol the endo,exo -bis(tetrahaptotricarbonyliron) isomer (C 12 H 12 )Fe 2 (CO) 6 (IIa)is the major product. The structure of this complex has been determined by X-ray diffraction.The asymmetric positions of the two Fe(CO) 3 groups with respect to the roof-shaped organic skeleton was used to induce either stereo-specific functionalisation of the uncoordianted endocyclic CC double bond or stereo-and regiospecific functionalisation of one of the two coordinated s-cis -butadiene groups of the pentaene. Thus, hydroboration/oxidation of Ila gave the endo-exo -bis(tetrahaptotricarbonyliron)isomer of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]octane-2-ol (IV). cis deuteration of the exocyclic double bond was achieved by treating IIa with D 2 /PtO 2 in n-hexane. Protonation of IIa by HCl/AlCl 3 /CH 2 Cl 2 to give the η 4 -diene : η 2 -ene : η 3 -dienyl cationic complex Va, followed by quenching of Va with NaHCO 3 /CH 3 OH, resulted in a 1,4-addition of methanol to one coordinated s-cis -butadiene system. In contrast, quenching with NaOCH 3 /CH 3 OH resulted in the corresponding 1,2-addition of methanol. This gave the η 4 -1,3-diene : η 4 -1,4-diene complex VIIIa in which, suprisingly, one Fe(CO) 3 group is coordinated to two CC double bonds in gauche positions with respect to each other.

The structure of orange HgI2. I. Polytypic layer structure

The metastable orange crystals of HgI(2) comprise three different crystal structures, all of which are built from corner-linked Hg(4)I(10) supertetrahedra. Two of them are end members with the maximum degree of order (MDO) of a polytypic layer structure; the third shows a three-dimensional linkage. This paper presents the determination from X-ray diffraction data of the tetragonal polytypic structures and their stacking disorder. Diffraction patterns show sharp Bragg reflections and rods of diffuse intensity with pronounced maxima. In a first step, the diffuse intensity was neglected and all maxima were treated as Bragg reflections. The crystal was supposed to be a conglomerate of the two MDO structures diffracting independently, and their parameters and volume ratio were refined against the single data set. The geometries and anisotropic displacement parameters of the layers in the two structures are shown to be nearly identical. Layer contacts in the two stacking modes are identical. The structures are fractal complications of the stable red form of HgI(2). In a second step, the stacking disorder has been quantitatively analyzed with a Markov chain model. Two probabilities describing next-nearest-layer interactions were visually adjusted to observed intensity profiles extracted from image-plate detector data. Results consistently show that the crystal comprises nearly equal volumes of MDO structures with an average domain thickness of about 5 layers or 30 A

Crystal structure and reactivity in solution of o-cyanobenzylbis(diphenylphosphino)ethyleneplatinum(II) tetrafluoroborate

Abstract X-ray analysis of crystalline o-cyanbenzylbis(dihenylphosphino)ethyleneplatinum(II) tetrafluoroborate shows that the complex is a dimer [Pt(o-CH2C6H4CN)(Ph2PCHCHPPh2)]22 (BF42 having linear PtNC bonds, even though molecular models indicate a favourable geometry for π-coordination of the nitrile moiety. The CN group remains σ-coordinated to the metal in solution and is very prone to nucleophilic attack by water, alcohols and amines, giving imide, iminoether and amidine complexes, respectivelly.

Dithiophosphinate complexes of the lanthanides. Preparation of the complexes [Ln{S2PR2}4][AsPh4], R = OMe, OPri. Determination of the crystal structurals for Ln = Ce, Er (R = OMe) and Ln = Nd, Ho (R = OPri)

Abstract Lanthanide ions react with the salts of the dithiophosphorus acids R2PS2H (R = OMe, OPri) in the corresponding alcohol to form the tetrakis anionic complexes which may be isolated as their tetraphenylarsonium salts. For R = OPri, the complexes of the heavy ions crystallise as solvates, the solvent being easily removed in vacuo. The crystal structures of the complexes [Ln{S2PR2}4] [AsPh4] have been determined from diffractometer data for Ln = Ce and Er, R = OMe; and Ln = Nd and Ho, r = OPri. [Ce{S2P(OMe)2}4] [AsPh4]: monoclinic, space group Cc with a = 14.762(3), b = 16.780(4), c = 19.890(3) A and β = 101.09(1)°, R = 0.041. [Er{S2P(OMe)2}4] [AsPh4]: isomorphous to the above with a = 14.626(3), b = 16.760(2), c = 19.718(1) A and β = 100.89(1)°, R = 0.056. [Nd{S2P(OPri)2}4] [AsPh4]: monoclinic, space group P21/c with a = 12.868(4), b = 24.966(4), c = 21.420(6) A and β = 102.32(2)°, R = 0.072. Ho{S2P(OPri)2}4] [AsPh4] · PriOH: monoclinic, space group P21/n with a = 14.401(3), b = 32.427(6), c = 15.168(2) A and β 93.46(1)°, R = 0.069. The lanthanide ions are surrounded by eight sulphur atoms (CeS = 2.969, NdS = 2.984, HoS = 2.865, ErS = 2.856 A) in an almost perfect D2d dodecahedral arrangement (mmmm isomer). The Ho complex contains a molecule of uncoordinated lattice solvent. The solid state structures are compared with results obtained from paramagnetic NMR experiments in solution.