Oscar Wittke

Azorellanol: A diterpenoid with a new carbon skeleton from Azorella compacta

Abstract A new diterpenoid, azorellanol (5), was isolated from the whole plant of Azorella compacta (Umbelliferae). The structure was established by using mainly one- and two-dimensional NMR techniques, whereas the absolute stereochemistry was determined by X-ray diffraction analysis. The diterpenoid (5) possesses a novel hydrocarbon skeleton for which we suggest the name azorellane A new diterpenoid, azorellanol, was isolated from whole plant of Azorella compacta (Umbelliferae). The structure was established by using mainly one-and two-dimensional NMR technique, whereas the absolute stereochemistry was determined by X-ray diffraction analysis. The diterpenoid possesses a novel hydrocarbon skeleton for which we suggested the name azorellane. Download : Download full-size image

Crystal structure and vibrational spectra of polyamine-copper(II) complexes

The structures of [Cu(en)(H2O)2]SO4 (I), [Cu(en)2](NO3)2 (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), β=105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P21/a, witha=7.978(2),b=9.982(4),c=8.218(3), β=111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P212121, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO42− ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)2, (en)2 and (en) are inferred in this study.

Spectra and structure of polyamine-copper(II) complexes. Infrared spectrum and normal coordinate calculations of mono(diethylenetriamine) copper(II) nitrate

Abstract The infrared spectrum of mono(diethylenetriamine)copper(II) nitrate has been obtained in the frequency range 4000-80 cm −1 . Assignments of fundamental frequencies in the coordination site, as well as in the free and bonded nitrates, were performed regarding the structure of the complex. Also, a normal coordinate analysis based on a simplified model, was carried out in order to distinguish the frequency position of some normal modes, such as the three different ν(CuN) and the two different ν(CuO) modes.

Dicyclohexylamine-Thiourea Clathrate

Abstract The reaction of dicyclohexylamine (DCHA) with thiourea leads to the formation of the inclusion compound DCHA(6 Thiourea). Room temperature, single crystal X-ray diffraction analysis shows the product has a trigonal structure, α=β=90°, γ=120°, a=b=15.801(2)A, c=12.451(3)A, which may be described as a thiourea matrix defining hexagonal cavities where the di-cyclohexylamine molecules are accommodated. 13C-cross polarization magic angle spinning (CP-MAS) NMR study indicates the guest inside the cavities has a relatively free rotation and that the channels are, concerning this amine, perfect van der Waals cavities. Thermal studies indicates that the structural identity of the thiourea matrix endures after a partial loss of amine.

Single-crystal Anisotropic Proton Conductivity in the Clathrate of the Hydrogen-diquinuclidine Ion Inserted in a Polyanionic Thiourea–chloride Matrix

The anisotropic proton conductivity of a large-sized single crystal of the supramolecular, commensurate host–guest inclusion compound constituted by a polyanionic thiourea–chloride matrix defining channels in which the diquinuclidinium cations [Q2H]+ are hosted is reported. Specimens in the millimetre scale display an anisotropy factor of about 100, with electrical conductivities along molecular channels of the order of 10-4 S cm-1 at room temperature.

Inclusion of a Protonated Amine in Thiourea-Chloride and -Bromide Matrix. Expected Ionic Conducting Materials

The reaction of thiourea with 1-azabicyclo[2,2,2]octane (quinuclidine) and quinuclidine hydrochloride or quinuclidine hydrobromide in ethanol/acetone mixture leads to the formation of the inclusion compounds (thiourea) 2 [(quinuclidine) 2 H] + Cl − and (thiourea) 2 [(quinuclidine) 2 H] + Br − , respectively. The crystal structure of the ternary proton-amine-thiourea complex may be described as the inclusion of the hydrogen-diquinuclidine cationic complex in a stacked form in the van der Waals cavities of a polyanionic thiourea-chloride and −bromide superstructure. Complete structure determination of the products was performed and show channel structure formed by monodimensional, non intersecting polimeric chains of thiourea molecules linked by chloride or bromide ions.

Stepwise substitution reactions of the (η5-C5Me5)Re(CO)2I2 complex: aryl-iodo and aryl-methyl derivatives trans-(η5-C5Me5)Re(CO)2(Ar) X, X = I and Me. X-ray structure of trans-(η5-C5Me5)Re(CO)2(Ph)I

Abstract The diiodo complex cis -( η 5 -C 5 Me 5 )Re(CO) 2 I 2 undergoes monosubstitution in reaction with arylcopper (ArCu) to produce the corresponding aryl-iodo complexes trans -( η 5 -C 5 Me 5 )Re(CO) 2 (Ar)I, Ar = phenyl and tolyl. These complexes have been fully characterized by using a combination of elemental analyses and IR, 1 H and 13 C NMR spectroscopy; additionally trans -( η 5 -C 5 Me 5 )Re(CO) 2 (Ph)I was studied by X-ray crystallography. This complex crystallizes in the monoclinic space group P 2 1 / m with a = 8.191(2), b = 17.471(4), c = 12.995(3) A , β = 93.97(2)°, V = 1832.6(7) A 3 and D calc = 2.107 g cm −3 for Z = 4. The refined structure gave R = 2.74% and wR = 2.98% for 2858 observed reflections. Further reaction of the aryl-iodo complexes with MeLi yields the corresponding aryl-methyl derivatives trans -( η 5 -C 5 Me 5 )Re(CO) 2 (Ar)Me. The full spectroscopic characterization of these complexes is also described in this paper.

Structure refinement of monoclinic V3S4

Abstract The structure of monoclinic V 3 S 4 was refined using single crystal X-ray data. This modification crystallizes isostructural with Cr 3 S 4 , space group C 2/ m with a = 1263.8(2) pm, b = 329.4(1) pm, c = 587.8(1) pm and β = 115.68(1)°. The sulfur-metal distances are quite similar to those reported for the hexagonal modification of V 3 S 4 . Nevertheless, the monoclinic modification leaves smaller empty channels than those observed in the hexagonal modification.

9-9′-Bifluorenylidene (BFD) complexes of ruthenium [{(η5-C5Me5)Ru}n(BFD)]x (x = 0, n = 1' x = 1+, n = 2): EPR and spectroelectrochemical studies. X-ray structure of [{(η5-C5Me5Ru}(BFD)](OSO2CF3)

Abstract [( η 5 -C 5 Me 5 Ru] + coordinates to the six-membered aromatic rings of the bifluorenylidene (BFD) chromophore to afford mononuclear [( η 5 -C 5 Me 5 )Ru(BFD)] + and dinuclear {[( η 5 -C 5 Me 5 )Ru] 2 9BFD)} 2+ compounds which could be isolated as trifluoromethane sulfonate salts, 1 (OTf) and 2 (OTf) 2 , respectively. The X-ray structure of 1 was determined and both compounds were studied by spectroelectrochemical methods and their reduced species by EPR.

IR AND 13C-NMR SPECTRAL PROPERTIES OF THE LAYERED INCLUSION COMPOUND BIS(THIOUREA)HEXAMETHYLENETETRAMINE

The structure of the 1: 2 adduct of hexamethylenetetramine and thiourea was reanalyzed reinterpreting X-ray diffraction data and providing additional IR and NMR spectroscopic features. The product is thus described as supramolecular commensurate host-guest complex corresponding to the intercalation of hexamethylenetetramine in a layered thiourea matrix. FT-IR spectra evidence a simultaneous strengthening of both C-N and C-S bonds, that appearing as a pattern characteristic for described layered thiourea matrix. 13CP MAS-NMR spectra of the intercalated hexamethylenetetramine is essentially determined by nuclear dipolar magnetic interactions and host-guest chemical interactions arising from 13C-14N residual dipolar interaction not averaged to zero by MAS-NMR and from the magnetic non-equivalence of the guest carbon atoms caused by the hydrogen bonding interaction with the thiourea matrix