Structure and conformational properties of carbonylbisimidosulfuryl fluoride, O=C(N=S(O)F2)2

The molecular structure and conformational properties of O=C(N=S(O)F₂)₂ (carbonylbisimidosulfuryl fluoride) were determined by gas electron diffraction (GED) and quantumchemical calculations (HF/3-21G* and B3LYP/6-31G*). The analysis of the GED intensities resulted in a mixture of 76(12)% syn–syn and 24(12)% syn–anti conformer (ΔH⁰=H⁰(syn–anti)−H⁰(syn–syn)=1.11(32) kcal mol⁻¹) which is in agreement with the interpretation of the IR spectra (68(5)% syn–syn and 32(5)% syn–anti, ΔH⁰=0.87(11) kcal mol⁻¹). syn and anti describe the orientation of the S=N bonds relative to the C=O bond. In both conformers the S=O bonds of the two N=S(O)F₂ groups are trans to the C–N bonds. According to the theoretical calculations, structures with cis orientation of an S=O bond with respect to a C–N bond do not correspond to minima on the energy hyperface. The HF/3-21G* approximation predicts preference of the syn–anti structure (ΔE=−0.11 kcal mol⁻¹) and the B3LYP/6-31G* method results in an energy difference (ΔE=1.85 kcal mol⁻¹) which is slightly larger than the experimental values. The following geometric parameters for the O=C(N=S)₂ skeleton were derived (r_a values with 3σ uncertainties): C=O 1.193 (9) Å, C–N 1.365 (9) Å, S=N 1.466 (5) Å, O=C–N 125.1 (6)° and C–N=S 125.3 (10)°. The geometric parameters are reproduced satisfactorily by the HF/3-21G* approximation, except for the C–N=S angle which is too large by ca. 6°. The B3LYP method predicts all bonds to be too long by 0.02–0.05 Å and the C–N=S angle to be too small by ca. 4°.     

The molecular structure of N-sulfinyl trimethylsilanamine, (CH3)3SiNSO

The geometric structure of (CH₃)₃Si---NSO in the vapour phase has been determined by gas electron diffraction. The molecule possesses a planar Si---N=S=O skeleton with syn conformation. The Si(CH₃)₃ group staggers the N=S double bond. The following skeletal parameters (r_a distances and angles with 3σ errors limits) were obtained: Si---N 1.750(6)Å, N=S 1.508(5)Å, S=O 1.444(4)Å, Si---N=S 133.9(9)°, N=S=O 122.5(10)°. Ab initio calculations (HF/3−21G*) were performed for H₃Si---NSO and confirm the planar syn structure for sulfinyl silanamines.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_{g(S---C2) = 1.719(2) Å}, r_{g(C2=C3) = 1.370(3) Å}, r_{g(C3---C6) = 1.497(6) Å}, r_{g(C2---H) = 1.101(5) Å}, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) - r(S=C₅) and r(C₂=C₃)-r(C₄ =C₅) were fixed at the 3–21G* value of 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Molecular structure of 3-methylthiophene studied by gas electron diffraction combined with microwave spectroscopic data

The molecular structure of 3-methylthiophene

has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: r_g(S---C₂) = 1.719(2) Å, r_g(C₂=C₃) = 1.370(3) Å, r_g(C₃---C₆) = 1.497(6) Å, r_g(C₂---H) = 1.101(5) Å, CSC = 91.6(2)°, SC₂C₃ = 113.3(5)°, SC₅C₄ = 111.3(3)°, C₂C₃C₆ = 123.2(11)° and C₃C₆H = 112(2)°. The values of r(S---C₂) − r(S---C₅) and r(C₂=C₃) − r(C₄=C₅) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit.     

Structural features of 4,4′-diaminooctafluorobiphenyl

Molecules of C₁₂H₄F₈N₂ crystallize in the orthorhombic space group P2₁2₁2₁ with cell constants a=9.200(1), b=10.896(1), c=23.178(3) Å and V=2323.4(5) ų. There are two molecules in the asymmetric unit which have D₂ symmetry. However these two molecules have C₂ symmetry in central C–C bonds, separately. Intramolecular steric repulsions between F atoms and N–HF hydrogen bonds have very much affected the molecular conformation. The mean dihedral angle between intramolecular phenyl rings is 119.2(1)°. The N–C bonds have lengths 1.363(4)–1.407(4) Å with a mean of 1.388 Å. This is shorter than the conventional C–N (1.47(1) Å) bond length due to π-electron delocalizations (F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. II (1987) S1–S19).

The molecular structure of the title compound was also investigated by IR spectroscopy. It was shown that the IR spectra are in agreement with the crystal structure. On the other hand, theoretical and semi-emprical molecular mechanic calculations were carried out to obtain the most probable low-energy conformations by using MM3, PM3 and AM1 programs.     

Molecular structure of 4,4′-sulfandiyl-bis-thiophenol from electron diffraction

The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C₁₂H₁₀S₃) has been determined by gas electron diffraction. Assuming identical geometry and D_2h local symmetry for ---SC₆H₄S--- moieties, the following bond lengths (r_g) and bond angles were obtained: C---H = 1.101 ± 0.005, S---H = 1.388 ± 0.019, (C---C)_mean = 1.400 ± 0.003, (S---C)_mean = 1.778 ± 0.004 Å, C_ar---S---C_ar = 103.5 ± 1.3, C---C(S)---C = 120.4 ± 0.3, C(H)---C(H)---H = 119.1 ± 0.9 and C---S---H = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C_arSC_ar plane; ₁ = 67.8 ± 2.0°, ₂ = 4.5 ± 7.2°, and ₁ = 69.4 ± 2.0δ, ₂ = −26.6 ± 7.1°. Identical signs of ₁ and ₂ indicate that the two benzene rings are rotated in the same direction about the respective S_central---C axes.     

Tautomeric properties, conformations and structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine

The crystal structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine (C₁₃H₁₀NO₂Cl) was determined by X-ray analysis. It crystallizes orthorhombic space group P2₁2₁2₁ with a=12.967(2) Å, b=14.438(3) Å, c=6.231(3) Å, V=1166.5(6) Å³, Z=4, D_c=1.41 g cm⁻³ and μ(MoK)=0.315 mm⁻¹. The title compound is thermochromic and the molecule is nearly planar. Both tautomeric forms (keto and enol forms in 68(3) and 32(3)%, respectively) are present in the solid state. The molecules contain strong intramolecular hydrogen bonds, N1–H1O1/O2 (2.515(1) and 2.581(2) Å) for the keto form and O1–H01N1 for the enol one. There is also strong intermolecular O2–HO1 hydrogen bonding (2.599(2) Å) between neighbouring molecules. Minimum energy conformations AM1 were calculated as a function of the three torsion angles, θ₁(N1–C7–C6–C5), θ₂(C8–N1–C7–C6) and θ₃(C9–C8–N1–C7), varied every 10°. Although the molecule is nearly planar, the AM1 optimized geometry of the title compound is not planar. The non-planar conformation of the title compound corresponding to the optimized X-ray structure is the most stable conformation in all calculations.     

Molecular structure of the azidoalane [Me2N(CH2)3]AltBu(N3). X-ray structural determination and ab initio calculations

A single crystal of the azidoalane [Me₂N(CH₂)₃]AltBu(N₃) (1a), grown in a capillary using a miniature zone melting procedure, was investigated by X-ray analysis. Compound 1a (C₉H₂₁AlN₄) is a monomeric species in the solid state, which crystallizes in the monoclinic space group P2₁ with a=6.8560(14) Å, b=12.251(3) Å, c=7.786(2) Å, β=108.51(3)° and Z=2. The results of the X-ray structural determination are compared with the calculated structure of 1a (HF/6-31G(d) and B3LYP/6-31G(d) level of theory). Whereas the overall agreement between the measured and calculated structure is good, the Al–N donor-bond length differs by 11 and 12 pm at the HF and B3LYP level, respectively. To evaluate the effects of a polar environment on the molecular structure of 1a self-consistent reaction field (SCRF) calculations at the HF and B3LYP level with the 6-31G(d) basis set were performed.     

The gas phase structure of tetrakis(trifluoromethylthio)ethene, CF3S)2C=C(SCF3)2

The geometric structure of (CF₃S)₂C=C(SCF₃)₂ in the vapour phase was determined by electron diffraction. The molecule possesses D₂ symmetry with the S---CF₃ bonds oriented perpendicular to the ethene plane, in alternating directions up-down-up-down. The following skeletal geometric parameters were obtained (r_a distances and angles, experimental uncertainties are 3σ values): C=C = 1.34Å (ass.), C(sp²---S = 1.761(5)Å, S---C(sp³) = 1.832(5)Å, S---C---C = 119.6(4)°, C---S---C = 100.6(13)°, and ø(C=C---S---C) = 90.9(11)°. The gas phase conformation differs considerably from the crystal structure, where the molecule possesses C_i symmetry and the CF₃ groups, which are bonded to cis-standing sulfur atoms, lie on the same side of the ethene plane with dihedral angles ø(C=C---S---C) of 117° and 127°.     

X-Ray, FTIR and quantum chemical studies of short and asymmetric hydrogen bonds in bis(2,6-dimethylpyridine-N-oxide) sulphate [2,6-(CH3)2C5H3N---OH]2[SO4]

Crystals of bis(2,6-dimethylpyridine-N-oxide) sulphate are monoclinic, space group P2₁/c, a = 14.098(2) Å, b = 7.855(1) Å, c = 15.203(3) Å, β = 104.84(1)°. The crystal structure has been refined to R = 0.0373 (2052 reflections). The disordered SO²⁻₄ anion accepts hydrogen bonds from two protonated 2,6-dimethylpyridine-N-oxides and two alternative conformations of the SO²⁻₄ group are distinguished. The occupancy factor of the predominant orientation is 0.63 and the O...O distances are 2.445(2) and 2.453(4) Å; in the second form (fraction, 0.37), these distances are 2.445(2) and 2.544(9) Å.

The PM3 and AM1 methods predict three minima for the title complex, whereas the SAM1 and BLYP/6-31G methods predict only one. All methods predict that molecular complex 3 is the most stable. The SAM1 geometry is very close to that of BLYP/6-31G.

The Fourier transform IR (FTIR) spectrum shows a very intense and broad (continuum) absorption within the 1600-400 cm⁻¹ region, typical of short hydrogen bonds. There is no absorption in the 3000-2000 cm⁻¹ region expected for the longer hydrogen bond (2.544(9) Å) in the less populated orientation. Isotope and solvent effects are discussed.     

The molecular structure and conformation of dichlorotetramethyldisiloxane as determined by gas phase electron diffraction

Dichlorotetramethyldisiloxane is studied by gas-phase electron diffraction at room temperature. The least-squares values of the bond distances (r_g) and bond angles () are: r(C---H)=1.084(5) Å, r(Si---O) = 1.624(2) Å, r(Si---C) = 1.852(2) Å, r(Si---Cl) = 2.067(2) Å, SiOSi = 154.0° (1.5), ClSiO = 110.2° (0.8), ClSiC = 109.6°(0.7), HCSi = 111.7°(1.5), OSiC = 110.0°(0.8), τ₁ (zero corresponds to the Si---Cl bond trans to the Si---O---Si linkage) = 78°(6) and τ₂ = 141°(19). A two-conformer model cannot be ruled out.     

Structural and spectral studies on N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea

The crystal and molecular structure of the N-(4-chloro)benzoyl-N′-(4-tolyl)thiourea (C₁₅H₁₃N₂OSCl, M_r=304.79) is determined by X-ray diffraction. The crystal structure is monoclinic, space group: P2₁/n, a=16.097(6), b=4.5989(2), c=19.388(7) Å and β=89.299(6)° V=1434.7(9)ų, Z=4. FTIR and NMR spectra have been characterized. The interactions of intramolecular and intermolecular hydrogen bonds have been discussed. Density functional theory (DFT) (B3LYP) methods have been used to determine the structure and energies of stable conformers. Minimum energy conformations are calculated as a function of the torsion angle θ (C13–N1–C14–N2) varied every 30°. The optimized geometry corresponding to crystal structure is the most stable conformation. This has partly been attributed to intramolecular hydrogen bonds. With the basis sets of the 6-311G* quality, the DFT calculated bond parameters and harmonic vibrations are predicted in a very good agreement with experimental data.     

The system CePO4–K3PO4

The phase diagram of the system CePO₄–K₃PO₄ has been determined based on investigations by differential thermal analysis, X-ray powder diffraction, IR spectroscopy and optical microscopy. The system contains only one intermediate compound K₃Ce(PO₄)₂, which melts incongruently at (1500±20)°C. This compound is stable down to room temperature and exhibits a polymorphic transition at 1180°C. It was confirmed that the low-temperature form β-K₃Ce(PO₄)₂ crystallizes in a monoclinic system, space group P2₁/m with unit cell parameters a=9.579 (5), b=5.634 (6), c=7.468 (5) Å; =γ=90°, β=90.81 (3)°; V=403.083 Å³.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

2D Cu(I) and 3D mixed-valence Cu(I)/Cu(II) coordination polymers: Synthesis and structural characterization of [CuCl(pyz-H)2]·2H2O and [Cu2Cl2(pyz)(H2O)]·H2O (pyz-H = pyrazinic acid)

Two new coordination polymers of copper(I) chloride and pyrazinic acid (pyz-H), namely [CuCl(pyz-H)₂]·2H₂O (1) and [Cu₂Cl₂(pyz)(H₂O)]·H₂O (2) have been prepared and characterized by spectroscopic, magnetic and crystallographic methods. The overall physical measurements suggest that 1 is diamagnetic and contains monodentate N-pyrazinic acid, whereas 2 is paramagnetic and contains tridentate N,N′,O- chelating bridging pyrazinato anion. In the structure of 1 as elucidated by X-ray single crystal analysis, the asymmetric units [CuCl(pyz)₂] are linked together forming a zigzag chain with tetrahedral copper(I) environment. The two lattice water molecules form hydrogen bonds with the uncoordinated N atom and carboxylate group O atom of pyz-H molecules. The Cu–N bond lengths are 2.009(6) Å and Cu–Cl distances are 2.337(2) Å. Complex 2 has a three-dimensional structure with the chains [Cu(I)Cu(II)(C₅H₃N₂O₂)Cl₂(H₂O)] interconnected by [Cu(I)Cl₂N] tetrahedral unit and [Cu(II)NO₂Cl₂] polyhedra. The Cu(I)–Cl and Cu(I)–N distances are 2.327(2)–2.581(2) Å and 1.988(6) Å, respectively, whereas the Cu(II)–Cl and Cu(II)–N bond lengths are 2.258(2), 2.581(2) Å, and 2.017(6) Å, respectively. Hydrogen bonds of the type O–HO are formed between lattice and coordinated water, and carboxylate oxygens of pyrazinato ligand giving rise to a three-dimensional network. The Cl⁻ anions act as bridging ligands in both complexes. The magnetic data of complex 2 have been measured from 2 to 300 K and discussed.     

Studies of π-bonding perturbation in the tungsten-nitrogen multiple bond of isopropylimido tungsten(VI) complexes: The crystal and molecular structures of [W(NCHMe2)Cl4]2·C6H6 and [W(NCHMe2)Cl5][NEt4]

¹³C NMR chemical shift data for the -carbon (δ) of a variety of tungsten isopropylimido complexes indicate that the extent to which the nitrogen lone pair participates in multiple bonding to tungsten depends on the form of the complex and the ligands involved. The structures of [W(NCHMe₂)Cl₄]₂·C₆H₆ (1a) and [W(NCHMe₂)Cl₅][NEt₄] (7) which show widely different δ values, have been determined by single-crystal X-ray diffraction methods. Crytals of 1a are triclinic space group P , with a = 6.394(2), b = 8.890(3), c = 11.205(2) Å and = 109.95(2)°, β = 98.91(2)°, γ = 93.96(2)°; crystals of 7 are orthorhombic, space group Pnma, with a = 13.667(5), b = 15.152(2), c = 9.432(2) Å. Both structures were solved by Patterson and Fourier methods and refined to an R value of 0.050 for 1325 observed data of 1a and to an R value of 0.050 for the 1157 observed data of 7. Complex 1a is dimeric with a W---N bond length of 1.697(12) Å and complex 7 is monomeric with a longer W---N bond length of 1.763(16) Å. Comparison of the W---Cl bond lengths and correlations with π-bonding to make an 18-electron count, indicates that the W---N bond lengths differ in the two complexes as a result of overall π-bonding requirements.     

((Fluoroformyl)imido)(trifluoromethyl)sulfur fluoride, FC(O)N = S(F)CF3: unexpected conformational properties

The geometric structure and conformational properties of ((fluoroformyl)imido)(trifluoromethyl)sulfur fluoride, FC(O)N = S(F)CF3, are investigated by gas electron diffraction (GED) experiments, IR (gas) spectroscopy, and quantum chemical calculations (HF, MP2, and B3LYP with 6-31G* basis sets). The GED intensities are reproduced best with a mixture of 79(12)% trans-syn and 21(12)% cis-syn conformers. "Trans/cis" describes the orientation around the S=N double bond (FC(O) group relative to sulfur substituents), and "syn" refers to the orientation of the C=O bond relative to the S=N bond. From the intensities of the C=O bands in the IR (gas) spectrum, a composition of 86(8)%:14(8)% is derived. These ratios correspond to delta G0(GED) = 0.79(36) and delta G0(IR) = 1.09(35) kcal mol-1. The preference of a trans structure, around the S=N double bond is unexpected, since all imidosulfur compounds studied thus far possess a cis configuration. The conformational properties are reproduced qualitatively correctly by all theoretical calculations. The predicted energy differences delta E(HF) = 2.41, delta E(MP2) = 0.64, and delta E(B3LYP) = 0.28 kcal mol-1 are larger or slightly smaller than the experimental values. Additional theoretical calculations (B3LYP) for several imidosulfur compounds reveal that only FC(O)N=S(F)CF3, with mixed substitution at sulfur and the FC(O) group bonded to nitrogen, prefers the trans structure.     

Structures of propionaldehyde, butyraldehyde, and pivalaldehyde complexes of the chiral rhenium fragment [(η-C5H5)Re(NO)(PPh3)]

The crystal structures of propionaldehyde complex (RS,SR)-(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₃)]⁺ PF₆⁻ (1b⁺ PF₆^s−; monoclinic, P2₁/c (No. 14), a = 10.166 (1) Å, b = 18.316(1) Å, c = 14.872(2) Å, β = 100.51(1)°, Z = 4) and butyraldehyde complex (RS,SR)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₂CH₃)]⁺ PF₆⁻ (1c⁺PF₆⁻; monoclinic, P2₁/a (No. 14), a = 14.851(1) Å, b = 18.623(3) Å, c = 10.026(2) Å, β = 102.95(1)°, Z = 4) have been determined at 22°C and −125°C, respectively. These exhibit C O bond lengths (1.35(1), 1.338(5) Å) that are intermediate between those of propionaldehyde (1.209(4) Å) and 1-propanol (1.41 Å). Other geometric features are analyzed. Reaction of [(η⁵-C₅H₅)Re(NO)(PPh₃)(ClCH₂Cl)]⁺ BF₄⁻ and pivalaldehyde gives [(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHC(CH₃)₃)]⁺BF₄⁻ (81%), the spectroscopic properties of which establish a π C O binding mode.     

Analytical potential energy function for the Van der Waals molecule He2Ne

A potential energy function has been derived for the two linear isomer structures He₂Ne⁺(X²Σ⁺) using ab initio calculations with the QCISD(T)/6–31++G(d,p) method. Because we use the reasonable dissociation limit (3) instead of the unacceptable one (1), our potential energy function represents considerable topographical features in detail, including the linear [He---Ne⁺---He] structure (R_HeNe = 1.4694 Å, R_He'Ne = 2.0069 Å HeNeHe = 180°) with two symmetric linear saddles (R_HeNe = R_He'Ne = 1.80 Å, HeNeHe = 180° and R_HeNe = 1.5 Å, R_He'Ne = 3.2 A°, HeNeHe = 180°), and the topographical minimum of the [He---He---Ne⁺] structure (R_HeHe = 2.2217 Å, R_HeNe = 1.4426 Å, HeHeNe = 180°), with a linear saddle (R_HeHe' = 3.0 Å, R_HeNe = 1.8 Å, HeHeNe = 180°).     

The molecular structure and conformation of trichloronitromethane as determined by gas-phase electron diffraction and theoretical calculations

The molecular structure of trichloronitromethane has been studied in the gas phase using electron diffraction data. The molecules are found to undergo low barrier rotation about the CN bond with a planar CNO₂ moiety in agreement with HF/MP2/B3LYP/6-311G(d,p) calculations. The experimental data are consistent with a dynamic model using a potential function for the torsion of V = (V₆/2)(1 − cos 6τ). The major geometrical parameters (r_g and ) for the eclipsed form, obtained from least squares analysis of the data are as follows: r(NO₃) = r(NO₄) = 1.213(2) Å, r(CN) = 1.592(6) Å, r(CCl)_av = 1.749(1) Å, Cl₅CN/Cl₆CN = 109. 6°/106.3°(2), O₃NC/O₄NC = 117. 6°/114.1°(4), τCl₅C₁N₂O₃ = 0.0°, and V₆ = 0.20(25) kcal/mol.