Metal-silicon bonded compounds : X. The molecular structures of 2,2,4,4,6,6,8,8-octamethyl-2,4,6,8-tetrasila-1,5-mercuracyclooctane and bis(triphenylsilyl) mercury

The crystal and molecular structure determinations of 2,2,4,4,6,6,8,8-octamethyl-2,4,6,8-tetrasila-1,5-mercuracyclooctane. Hg₂Si₄C₁₀H₂₈ (I) and of bis-(triphenylsilyl)mercury, (Ph₃Si)₂Hg (II), are reported. The structures have been determined from single-crystal X-ray data collected by counter methods. Both molecules crystalize in the space group P1 with one centrosymmetric molecule per unit cell. Each structure contains linear SiHgSi groups, with mercury-silicon distances of 2.490(4) Å in I and 2.503(4) Å II. In compound I the SiHgSi groups are linked by methylene bridges which form an eight member ring in the chair conformation. The cell dimensions for compound I are a 6.277(2), b 8.408(2), c 9.274(4) Å, α 92.75(3), β 94.79(3) and γ 100.14(2)° with R₁0.062 for 1809 observed reflections. The cell dimensions for compound II are a 9.999(4), b 11.727(8), c 7.654(5) Å, α 99.87(5), β 115.35(4) and γ 98.41(4)°, with R₁0.081 for 2394 observed reflections.     

The structures of 5-methyl-5-phenyl-5H-dibenzo[b,f] silepin and its saturated analog

The structures of 5-methyl-5-phenyl-5H-dibenzo[b,f] silepin (I) and 5-methyl- 5-phenyl-1O,11-dihydro-5H-dibenzo [b,f] silepin (II) have been determined from three-dimensional X-ray data collected by counter methods. I crystallizes in the orthorhombic space group Pnam with a 7.596(3), b 18.102(5) and c 12.190(2) Å; observed and calculated densities (Z = 4) are 1.17 and 1.18 g cm^?3, respectively. II crystallizes in the monoclinic space group $\text{P}\text{2}{}_1\text{c}$ with a 11.115(3), b 7.920(3), c 20.765(5) Å and β 111.71(2)°; observed and calculated densities (Z = 4) are 1.17 g cm^?3. Anisotropic refinement of nonhydrogen atoms, with hydrogen atoms included at fixed ideal locations, gave conventional R-factors of 4.5% (I) and 5.0% (II). Compound I exhibits the boat conformation for the tricyclic framework and is located on a crystallographically required mirror plane. Com- pound II has the expected folded boat conformation. The torsion angle about the 10,11-bond is 0.0° for I, a crystallographic symmetry requirement, and 89.9° for II. Mean SiC bond distances are 1.863 Å(I) and 1.875 Å(II). The dihedral angles between the planar benzo groups are 129.7° (I) and 137.2° (II); introduc- tion of unsaturation at the 10,11-position decreases the dihedral angle in the tri- cyclic system, i.e., the tricyclic system is more bent.     

Conformational flexibility of dehydroalanine derivatives. Crystal and molecular structure of 2-N-acetyldehydrophenylalanyl-l-proline

The molecular structure of the title compound has been determined from three-dimensional X-ray data. C₁₆H₁₈N₂O₄·$\text{1}\text{2}$H₂O is monoclinic, space group C2, with Z=4 in a cell of dimensions: a = 18.508(3), b = 9.517(4), c = 10.538(4) Å, β = 120.00(3)°. One water molecule coordinates four molecules in a tetrahedral arrangement. The conformation of this molecular system is discussed also on the basis of the known structure of related compounds and previously reported theoretical results.     

Crystal and molecular structure of 5-ethyl-5,10-dihydrido-10,10-diphenylphenazasiline

The structure of 5-ethyl-5,10-dihydro-10,10-diphenylphenazasiline has been determined from three-dimensional X-ray data collected by counter methods. The compound in the monoclinic space group P2₁/b with a 10.782(5), b 22.642(9), c 8.830(4) Å and γ 74°41′(2). The observed and calculated densities (Z = 4) are 1.22 and 1.21 g cm^-3, respectively. Anisotropic(Si, N, C)-isotropic block-diagonal least squares refinement gave a conventional R factor of 3.9% for 1871 reflections with I>2σ(I). The central six-membered ring of the tricyclic system adopts a boat conformation; the dihedral angle between the benzo-group planes is 157.3°. The CSiC angle in the heterocycle is 101.1(1)°; the mean SiC bond length is 1.850(2) Å (in the cycle) and 1.862(2) Å (with Ph group). The nitrogen atom is displaced 0.05 Å from the plane of the adjacent carbon atoms; the sum of the angle about N is 359.7°.     

Crystal structure and conformation of N,N′-bis (3,5-dichlorosalicylidene)-2-hydroxy 1,3 diamino-2-propan

N,N′-bis(3,5-dichlorosalicylidene)-2-hydroxy-1,3-diamino-2-propan (C₁₇H₁₄Cl₄N₂O₃) was synthesized and its crystal structure determined. It crystallizes in the monoclinic space group, C2/c, with a=29.734(8), b=4.541(1), c=14.694(2) Å, β=115.85(2), R(F²)=0.048 for 1704 independent reflections. The title compound has a twofold axis passing through the central C9 atom. The intramolecular hydrogen bond occurs between the pairs of atoms N1 and O1 [2.648(5) Å] and the hydrogen atom is essentially being bonded to the nitrogen atom. There is no intermolecular proximity between molecules. Conformations of the title compound were investigated by semi-empirical quantum mechanical AM1 calculations. The optimized geometry of the molecular structure corresponding to the non-planar conformation is the most stable conformation in the theoretical calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded steric interactions.     

The crystal structure of a tricarbonyliron-substituted cyclobutadiene complex: Tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c]cyclobuta[f]cyclooctene-3,12-dione] iron

The crystal structure of tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c] cyclobuta[f] cyclooctene-3,12-dione] iron, C₂₀O₂H₁₄Fe(CO)₃, has been determined by the single crystal X-ray diffraction technique using data collected with a fully automated diffractometer. The unit cell is monoclinic, space group P2₁/c with a = 12.025(2), b = 23.204(3), c = 14.614(2) Å, β = 102.16(2)°, and contains eight molecules (two per asymmetric unit). The structure was elucidated to study the coordination of the iron atom and to correlate the conformation of the eight-membered ring with an NMR study. The final structure was obtained by Patterson-superposition and Fourier techniques and refined by full-matrix least-squares to a crystallographic residual of 0.070. In both independent molecules the iron atom is 1.77 Å from the cyclobutadiene ring to which it is coordinated. The eight-membered ring is flattened from a boat conformation and the six-membered rings are twisted from coplanarity by an angle of 74°. The twist is such that if one ring points above the eight-membered ring, the other ring will point below it with concomitant pointing in the opposite sense by neighboring carbonyl groups. Such a structure has conformational chirality. It is postulated that the stability of each enantiometer is due to the particularly high energy of the transition state through which each would pass to achieve inter-conversion.     

A cationic dicarbene complex of iron. The crystal structure of [Fe(CO)2(S2CNMe2)(CNMe2)2S]PF6 · 12C2H4Cl2

The structure of the compound [Fe(CO)₂(S₂CNMe₂)(CNMe₂)₂S]PF₆ · $\text{1}\text{2}$C₂H₄Cl₂ has been determined by X-ray crystallography. The compound crystallizes in space group C2/c with eight formula units in a unit cell of dimensions a 23.939(18), b 15.771(7), c 12.314(4) Å, β 92.01(5)°. Full-matrix least-squares refinement of 2084 counter data yielded R = 0.051. The complex cation contains an unusual chelating dicarbene ligand, and the structure of this complex is compared with related species. The bonding properties of the dicarbene ligand are discussed.     

The structure of 5-p-N,N-dimethylaminophenyl-10,11-dihydro-5H-dibenzo[b,f]silepin

The structure of 5-p-N-N-dimethylaminophenyl-10,11-dihydro-5H-dibenzo-[b,f]silepin has been determined from three-dimensional X-ray data collected by counter methods. The compound crystallizes in the monoclinic space group P2₁/ca  14.121(4), b  14.379(3), c  9.126(2) Å and β = 99.57(2)°. The observed and calculated densities (Z  4) are 1.19 and 1.20 g cm^?3, respectively. Anisotropic refinement of nonhydrogen atoms with hydrogen atoms at fixed calculated positions gave a conventional R-factor of 4.6% for 2023 reflections with F$\text{2}\text{0}$ > 3σ(F²₀). The central seven-membered ring of the tricyclic system exhibits a folded boat conformation; the dihedral angle between the benzo groups is 137.2°. The benzo groups are twisted approximately 21° relative to one another and skewed such that the two carbons bonded to silicon are 0.33 Å closer to one another than the two benzo ring carbons one atom removed from the silicon. The nitrogen atom is displaced 0.04 Å from the plane of the adjacent carbon atoms.     

Synthesis, characterization, crystal and molecular structure analysis of N-(2,4-dimethylphenyl)-6-methyl-4-(3-nitrophenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxamide

A novel dihydropyrimidine (DHPM) derivative bearing a carbamoyl moiety was synthesized by an efficient three-component Biginelli reaction and was characterized spectroscopically and finally confirmed by X-ray diffraction studies. The title compound C₂₀H₂₀N₄O₄ crystallizes in the monoclinic space group P2₁/c with cell parameters a=12.8970(12) Å, b=13.6210(11) Å, c=11.8420(13) Å, β=115.860(3)°, Z=4 and V=1872.0(3) Å³. The conformation of the dihydropyrimidine ring is unusual; it is planar instead of the usual boat-like conformation. The 3-nitrophenyl ring is orthogonal to the 3,4-DHPM ring. The carbonyl group is in an anti-clinal conformation.     

A Novel Boron-Rich Scandium Borocarbide; Sc4.5−xB57−y+zC3.5−z(x=0.27, y=1.1, z=0.2)

A novel ternary boron-rich scandium borocarbide Sc_4.5−xB_57−y+zC_3.5−z (x=0.27, y=1.1, z=0.2) was found. Single crystals were obtained by the floating zone method by adding a small amount of Si. Single-crystal structure analysis revealed that the compound has an orthorhombic structure with lattice constants of a=1.73040(6), b=1.60738(6) and c=1.44829(6) nm and space group Pbam (No. 55). The crystal composition ScB_13.3C_0.78Si_0.008 calculated from the structure analysis agreed with the measured composition of ScB_12.9C_0.72Si_0.004. The orthorhombic crystal structure is a new structure type of boron-rich borides and there are six structurally independent B₁₂ icosahedra I1—I6, one B₈/B₉ polyhedron and nine bridging sites all which interconnect each other to form a three-dimensional boron framework. The main structural feature of the boron framework structure can be understood as a layer structure where two kinds of boron icosahedron network layer L1 and L2 stack each other along the c-axis. There are seven structurally independent Sc sites in the open spaces between the boron icosahedron network layers.     

Crystal and molecular structure of 9-methyl-9-phenyl-9,10-dihydro-9-sila-3-azaanthrone

The crystal and molecular structure of 9-methyl-9-phenyl-9,10-dihydro-9-sila-3-azaanthrone has been determined from three-dimensional X-ray diffraction data. The title compound crystals are monoclinic, space group P2₁/b, a = 12.818(2), b = 16.508(2), c = 7.694(1) Å,γ = 105°, 34′(2), Z = 4 and D_cal = 1.278 g cm^?3. The structure was determined by direct methods and refined by full-matrix least-squares calculations in the block-diagonal anisotropic approximation for non-hydrogen atoms to R = 0.043 for 2190 independent reflections, registered at room temperature. This is the first crystal structure determination of a Si-dihydroanthracene derivative with two heterocycles and a planar carbon atom in the C10-position. The tricyclic fragment takes up a planar configuration, the silicon atom having a tetrahedral surrounding, with an endocyclic angle of 103.7(1)° and average bond length SiC, 1.862(1) Å. The CO, 1.220(2) Å, bond length in the carbonylic group exactly corresponds with the double bond length. Average distance NC is 1.335(3) Å, angle CNC, 116.5(2)°.     

Spectroscopic and magnetic properties of a new class of two-dimensional bitriazole compounds: The X-ray structure of poly-bis(thiocyanato-N)-bis-μ-(4,4′-bis-1,2,4-triazole-N1,N1′)-cobalt(II) monohydrate

The synthesis of a new class of two-dimensional triazole compounds is described, including the crystal structure of [Co(NCS)₂(btr)₂]H₂O [btr stands for 4,4′-bis-1,2,4-triazole (C₄H₄N₆)]. Crystals are monoclinic, space group C2/c, a = 11.159(1) Å, b = 13.047(4) Å, c = 12.993(3) Å, β = 91.81(2)°, Z = 4. The structure has been solved by Fourier and direct methods and refined by full-matrix least squares to R = 0.0229, R_w = 0.0283. The structure consists of layers of six-coordinated cobalt atoms, each having two trans-oriented N-bonded thiocyanate groups [CoNCS 2.098(2) Å] and linked together in the equatorial plane by single bridges of btr to a two-dimensional network. The btr ligand coordinates through its N(1) and N(1′) atoms [CoN 2.128(1) and 2.142(1) Å]. The intralayer CoCo distance is 9.207(2) Å, and the inter-layer CoCo distance is 8.584(1) Å. The magnetic susceptibilities of the compound and of the isostructural nickel and iron compounds are discussed. The iron compound exhibits a high-spin-low-spin crossover at liquid-nitrogen temperatures, as shown by magnetic susceptibility.     

X-ray crystal structure of the clathrate compound tetrakis[(benzonitrile)(triphenylphosphorane)nickel(0)] · 2 toluene · ~1 n-hexane · ~1 cycloocta-1,5-diene

The preparation and the chemical properties of the clathrate compound tetrakis[(benzonitrile)(triphenylphosphorane)nickel(0)] · 2 toluene · ~1 n-hexane · ~1 cycloocta-1,5-diene are described. The crystal and molecular structure of this compound were determined from X-ray diffractometer data. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.117 for 3441 independent reflections. The crystals are monoclinic, space group P2₁, with Z = 2, in a unit cell of dimensions a 14.680(7), b 28.198(18), c 15.482(8) Å, β = 118.43(8)°. Eight (NiP(C₆H₅)₃ · NCC₆H₅) formula units are present as two tetrameric molecules in the unit cell. Each Ni atom of the tetramer is linked by σ bonds to a P and N atom and by π bonds to the NC group of another benzonitrile molecule. The coordination of the nickel atoms is roughly trigonal. The nickel and N atoms form an eight-membered ring with a boat conformation. The NCC groups of the benzonitrile residues are bent and the NC distances indicate a high degree of double bond character for all these bonds. The triphenylphosphorane groups adopt a “propeller”-like conformation. Four solvent molecules 2 toluene, 1 n-hexane, and ~1 cycloocta-1,5-diene per asymmetric unit are present in the unit cell.     

Synthesis and crystal structure of (S)-(+)-2-[(1,1-dimethylethoxy)carbonyl] amino-2-phenylethanol

The preparation and the crystal structure of the title compound are described. C₆H₅CH[NHCOOC(CH₃)₃]CH₂OH is monoclinic with the following unit-cell dimensions: a = 10.354(2), b = 6.533(3), c = 10.505(1) Å, β = 98.58(1)∘. The space group is P2₁ and Z = 2. The crystal-structure determination was run by using 1481 independent reflexions with a final R value of 0.033 (R_w = 0.043).     

The uniqueness of the propyl compound in the series (CnH2n+1NH3)2MnCl4 with n = 1–10

The perovskite-like layer structures of (C_nH_2n+1NH₃)₂MnCl₄ with n = 1–10 have been investigated by X-ray methods to determine their lattice constants and the temperature of transition to the respective zero-tilt phases. It has been found that the propyl compound is distinctive in that it exhibits the highest temperature of transition to a zero-tilt phase, the longest MnCl bond, and the largest difference between the a and b lattice parameters. Furthermore, it undergoes a large number of phase transitions (five), some of which are accompanied by the formation of commensurable or incommensurable superstructures. The special position of this compound is attributed to geometrical peculiarities related to the terminal methyl groups. The propyl compound is the only member of the series in which coupled movements of terminal methyl groups of neighboring strata do not seem to be important below 400°K.     

The crystal and molecular structure of dl-BI-(o-trimethyl-cis-brazilane)

X-ray crystallographic analysis has established the crystal and molecular structure of the title compound, C₃₈H₃₈O₈. The monoclinic crystals belong to the centrosymmetric space group P2₁/c, with a = 16.701(5), b = 8.037(2), c = 23.600(9) Å, β = 93.10(2)° and Z=4. The structure was solved by direct methods from diffractometer data measured with CuKα radiation, and refined to a final R index of 0.081 for the 2088 observed terms. The dimeric molecule has approximate two-fold symmetry and its presence in the unit cell in both chiralities forms a racemic structure. The three central bonds, C(10)-C(11), C(11)-C'(11), C'(11)-C'(10), are significantly elongated with a mean value 1.59 Å.     

Crytal and molecular structure of hydrido(trichlorostannyl)bis-cyclopentadienyl molybdenum(η5-C5H5)2Mo(H)SnCl3

On the basis of X-ray analysis the crystal and molecular structures of (η₅-C₅H₅)₂Mo(H)SnCl₃ have been determined. The compound crystallizes in the monoclinic system with parameters: a = 8.313(3), b = 13.109(4), c = 6.384(2) Å, β = 106.52(2)°, space group P2₁/m, R = 0.028. The conformation occurring in Cp₂Mo(H)SnCl₃ is that with the maximum repulsion between the chloride atoms and the cyclopentadienyl rings. The hydride H atom is shielded by the cyclopentadienyl groups and chlorine atoms, which accounts for the compound's stability to oxygen and hydrolysis.     

The crystal structure of tetrakis(methyldiphenylphosphine)iridium(I) tetrafluoroborate with cyclohexane of solvation: Ir[P(C6H5)2CH3]4BF4 - C6H12

The crystal structure of tetrakis(methyldiphenylphosphine)iridium(I) tetrafluoroborate with cyclohexane of solvation, [Ir(PPh₂Me)₄]BF₄·C₆H₁₂, has been determined from a three-dimensional X-ray analysis. The compound has been analysed in space group C₂/c of the monoclinic system. There are twelve molecules (i.e. 1.5 molecules per asymmetric unit) in a cell of dimensions a = 36.804(8), b = 22.93(2), c = 21.676(4) Å, β = 121.41(1)°. Block-diagonal least-squares refinement has given a final R-factor of 0.060 for 7905 reflections having I > 3σ(I).The structure consists of two crystallographically distinct, but structurally similar molecules, one on a general position and one on a crystallographic two-fold axis. The phosphine ligands around the iridium atoms are in a very distorted square-planar arrangement. The reactions of the cation axe discussed in terms of this structure.     

Cyclic polysilanes : VIII. The crystal structure of 1,2,3,4-tetra-tert-butyl-tetramethylcyclotetrasilane

The crystal structure of [Si(CH₃)(t-C₄H₉)]₄ has been determined by single crystal X-ray diffraction. The crystals are tetragonal, P4₂/n; a = b = 13.069(4), c = 7.880(2) Å, Z = 2. The structure was determined using 745 independent data and refined with anisotropic least-squares to a final unweighted R-value of 3.5%. Each tetrameric molecule was found to be arranged about a $\text{4}$ axis, with the independent crystallographic unit comprising one silicon atom, one methyl and one tert-butyl group. The four-membered ring of silicon atoms is nonplanar with an unusually large dihedral angle of 36.8°. The principal mean bond lengths are SiSi 2.377(1), SiC(methyl) 1.893(4), SiC(tert-butyl) 1.918(3) Å, and the SiSiSi bond angle is 86.99°. The SiSi bond length is somewhat longer than in other polysilanes.     

The Crystal Structure of (2 R, 7 S, 10 R)-2,10-diamino-5,5,7-trimethyl-4,8-diazaundecanenickel (II) perchlorate

The structure of the title compound, a tricyclic Ni(II) tetra-amine complex has been determined from analysis of photographic X-ray data. The crystal system is orthorhombic, space group P2₁2₁2₁, with unit cell dimensions a = 9.802, b = 8.998, c = 24.378 Å. The Ni atom is square planar coordinated. The six-membered chelate ring has a chair conformation. One of the five-membered chelate rings has a distorted gauche (λ) conformation with the methyl substituent in an equatorial position, the other has an unsymmetrical gauche (δ) conformation with the methyl substituent axial.