Preparation and Structural Characterization of Methylmercury(II) Complexes of 5-Aza- and 6-Azauracil Derivatives

1987 ◽  
Vol 42 (12) ◽  
pp. 1556-1562 ◽  
Author(s):  
W. S. Sheldrick ◽  
S. Heeb
Keyword(s):  
Structural Analysis ◽  
Binding Sites ◽  
Ionic Complex ◽  
X Ray ◽  
H Nmr ◽  
Ph Values ◽  
Nmr Data ◽  
Wide Ph Range ◽  
Ph Range

Abstract1:1 Methylmercury(II) complexes of the anti-tumour agent 6-azauracil (6AUH2) and its deriva­tives 6-azathymine (6ATH2). 1-methyl-6-azauracil (6AMUH) and 1-methyl-6-azathymine (6AMTH) have been isolated from aqueous solutions of CH3HgOH and the respective base. N3-Coordination was established by X-ray structural analysis for both [(CH3Hg)6 AUH] (1) (pH 6-8) and [(CH3Hg)6 AMT] (5) (pH 4-12); in addition 1H NMR data are in accordance with an identical binding site in the complexes [(CH3Hg)6AMU] (3) and [(CH3Hg)6 ATH] (4). Using an excess of CH3HgOH. 2:1 complexes with N1, N3-coordination may be prepared for both 6 AUH: and 5 AUH2 in a wide pH range (4-12 and 6-12 respectively). At pH values of 3-4 a 3:1 complex [(CH3Hg)35 AU]NO3 (7), with N1, N3, N5-coordination may be isolated: the binding sites were confirmed by X-ray structural analysis. In no case could an ionic complex with N6- coordination be isolated for a 6-azapyrimidine derivative. The binding preferences of the bases are discussed in the light of MNDO calculations.

Characterisation of Metal Binding Sites for 8-Azaguanine and 8-Azahypoxanthine Derivatives Synthesis and X-Ray Structural Analysis of Methylmercury(II) and Zinc(II) Complexes

1986 ◽  
Vol 41 (9) ◽  
pp. 1117-1122 ◽  
Author(s):  
W. S. Sheldrick ◽  
P. Bell
Keyword(s):  
Structural Analysis ◽  
Binding Site ◽  
Metal Binding ◽  
Binding Sites ◽  
Antineoplastic Agent ◽  
X Ray ◽  
Metal Binding Sites ◽  
Ph Values ◽  
Ph Range

Abstract The complexes [(CH3Hg)AGuaH ] (1) and [(CH3Hg)2AGua] • H2O (2) have been isolated from aqueous 1:1 and 2:1 solutions of CH3HgOH and 8 -azaguanine (AGuaH2) at respective pH values of 5 and 9. Only one CH3Hg+ complex of 8 -azahypoxanthine (AHxH2), namely [(CH3Hg)2AHx] (3), could be isolated under analogous conditions. X-ray structural analyses established N1 and N9 as metal binding sites in 3 and N9 as the coordination position in [Zn(H2O)4(AHxH)2] (4). With 8-aza-9-benzylhypoxanthine (9-BzAHxH) only one CH3Hg+ complex [(CH3Hg)9-BzAHx] (5) could be isolated in the pH range 2-10. N1 was established by X-ray structural analysis as the binding site. The relevance o f these findings to an understanding of ligand behaviour of the antineoplastic agent 8 -azaguanine is discussed.

Preparation and characterization of some ruthenium(II) porphyrins containing tertiary phosphine axial ligands, including the crystal structure of (octaethylporphinato)bis(triphenylphosphine)ruthenium(II)

1984 ◽  
Vol 62 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Sara Ariel ◽  
David Dolphin ◽  
George Domazetis ◽  
Brian R. James ◽  
Tak W. Leung ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phosphine Ligands ◽  
Tertiary Phosphine ◽  
X Ray ◽  
Porphyrin Complex ◽  
H Nmr ◽  
Axial Ligands ◽  
Nmr Data ◽  
Phosphine Complex

The ruthenium(II) porphyrin complex Ru(OEP)(PPh3)2 (OEP = the dianion of octaethylporphyrin) has been prepared from Ru(OEP)(CO)EtOH, and the X-ray crystal structure determined; as expected, the six-coordinate ruthenium is situated in the porphyrin plane and has two axial phosphine ligands. Synthesized also from the carbonyl(ethanol) precursors were the corresponding tris(p-methoxyphenyl)phosphine complex, and the Ru(TPP)L2 (TPP = the dianion of tetraphenylporphyrin, L = PPh3, P(p-CH3OC6H4)3, P″Bu3) and Ru(TPP)(CO)PPh3 complexes. Optical and 1H nmr data are presented for the complexes in solution. In some cases dissociation of a phosphine ligand to generate five-coordinate species occurs and this has been studied quantitatively in toluene at 20 °C for the Ru(OEP)L2 and Ru(TPP)L2 systems.

Spectroscopic and X-Ray Investigation of Cobalt(III) Complexes with 2-Oximinocarboxylic Acids

1993 ◽  
Vol 48 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Rostislav D. Lampeka ◽  
Zamira D. Uzakbergenova ◽  
Victor V. Skopenko
Keyword(s):  
Electronic Absorption Spectra ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
Octahedral Structure ◽  
Space Group ◽  
X Ray ◽  
H Nmr ◽  
Nmr Data ◽  
R Factors

Mixed complexes of Co(III) with 2-oximinopropionic (H2A) or 2-oximino-3-phenylpropionic (H2B) acid and different amine (imidazole, benzimidazole, pyridine, β-picoline, γ-picoline) are reported. Characterization of the complexes was based upon elemental analysis, conductivity and JR, 1H NMR, and electronic absorption spectra, and X-ray diffraction analysis. The organic ligands behave as O,N donors via the carboxyl oxygen and the oxime nitrogen atoms. A trans-octahedral structure has been assigned to the bis(2-oximinocarboxylato)bis(amine)cobalt(III) on the basis of 1H NMR data.The crystal and molecular structures of the complexes trans-[bis(2-oximinopropionato)bis-(imidazole)]- (I) and trans-[bis(2-oximinopropionato)bis(pyridine)]cobalt(III) (II) were determined. I crystallizes in space group P2/n with a = 14.1 67(2), b = 8.774(1), c = 14.785(2) Å,β = 113.37(1)°, Z = 4, Dcalc = 1.568 g · cm-3. II crystallizes in space group P1̄ with a = 9.122(2), b = 10.038(2), c = 11.759(2) Å, α = 69.95(1)°, β = 67.47(2)°, γ = 69.49(2)°, Ζ = 2, Dcalc = 1.547 g cm-3. The structures were refined to unweighted R factors of 0.036 and 0.028, respectively. The coordination sphere around Co is pseudo-octahedral with the 2-oximinopropionato ligands occupying four equatorial positions, and the amines in axial positions.

Structural Characterization Of Rh(Iii) Complexes Containing The Polypyridyl Ligands And Some Properties Of Their Derivatives

2001 ◽  
Vol 56 (8) ◽  
pp. 747-752 ◽  
Author(s):  
Mee Y. Kim ◽  
Won K. Seok ◽  
Heung N. Lee ◽  
Sung H. Han ◽  
Yongkwan Dong ◽  
...  
Keyword(s):  
X Ray Diffraction ◽  
Chloride Complexes ◽  
Polypyridyl Ligands ◽  
X Ray ◽  
H Nmr ◽  
Rhodium Chloride ◽  
Nmr Data ◽  
Elemental Analyses ◽  
Rhodium Atom

The structures of the compounds [Rh(bpy)2(py)(Cl)](ClO4 )2 (2 (ClO4 )2) and [Rh(phen)2(py)- (Cl)](ClO4 )2 (7 -(ClO4 )2) were determined by single-crystal X-ray diffraction. Both complexes show a six-coordinate rhodium atom with two bpy or phen ligands in the cis configuration. The Rh-Cl distances are 2.334(3) and 2.323(2) Å, respectively. The bond angles N-Rh-Cl formed with the axially-positioned nitrogen atom are 174.4(2) and 173.8(2)°. The oxidation of aquo complexes, prepared from the corresponding rhodium chloride complexes, by two equivalents of Ce(IV) in 60% HCIO4 solution yields the corresponding mono-oxo products. All complexes have been identified and characterized by elemental analyses, IR, and 1H NMR data

Stereostructure of slovanolides: X-ray crystallography of the 3-oxo-4αH,8α-benzoyloxy-10β,11α-diacetoxyslovanolide

1984 ◽  
Vol 49 (12) ◽  
pp. 2790-2800 ◽  
Author(s):  
Urszula Rychłewska ◽  
Miroslav Holub ◽  
Miloš Buděšínský ◽  
Zdenka Smítalová
Keyword(s):  
Structural Analysis ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Nmr Data

X-Ray structural analysis of 3-oxo-4αH,8α-benzoyloxy-10β,11α-diacetoxyslovanolide (XII) confirmed the correctness of the previously proposed structure of slovanolides. A comparison of the X-ray and 1H NMR data of lactone XII showed that the confirmation of this substance in crystals and in chloroform or benzene solutions is very similar. The structure of the lactone from Laserpitium marginatum has been corrected to formula XIa.

Preparation and characterization of some ruthenium(III) porphyrins, including the crystal structure of bromo(octaethylporphinato)(triphenylphosphine)ruthenium(III)

1984 ◽  
Vol 62 (7) ◽  
pp. 1239-1245 ◽  
Author(s):  
Brian R. James ◽  
David Dolphin ◽  
T. W. Leung ◽  
Frederick W. B. Einstein ◽  
Anthony C. Willis
Keyword(s):  
Crystal Structure ◽  
Cation Radical ◽  
Hydrogen Halides ◽  
X Ray ◽  
Radical Intermediates ◽  
H Nmr ◽  
Nmr Data ◽  
Paramagnetic Shifts

Some ruthenium(III) complexes Ru(porp)(L)X and [Ru(porp)L2]X, (porp = dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP); L = PPh3, P″Bu3; X = Br, Cl) have been prepared from the precursor complexes Ru(porp)L2 or Ru(porp)(CO)L using as oxidant the halogens, or air in the presence of the hydrogen halides. The X = PF6 salts can be made using Et3O+PF6− as oxidant. Ruthenium(II) porphyrin π-cation radical intermediates have sometimes been detected. The X-ray crystal structure of Ru(OEP)(PPh3)Br, the first reported for a ruthenium(III) porphyrin, reveals that metal is displaced 0.049 Å from the plane of the pyrrole N atoms towards the phosphine. The Ru(OEP)(py) Br and [Ru(OEP)(py)CH3CN]PF6 complexes have been synthesized from Ru(OEP)(CO)py. The ruthenium(III) complexes are low-spin as shown by magnetic and esr data. Optical and 1H nmr data, the latter showing large paramagnetic shifts, are also presented.

Reduction of antimony by nano-particulate magnetite and mackinawite

2008 ◽  
Vol 72 (1) ◽  
pp. 185-189 ◽  
Author(s):  
R. Kirsch ◽  
A. C. Scheinost ◽  
A. Rossberg ◽  
D. Banerjee ◽  
L. Charlet
Keyword(s):  
Oxidation State ◽  
Photoelectron Spectroscopy ◽  
Redox Processes ◽  
Environmental Behaviour ◽  
X Ray ◽  
Ph Values ◽  
Wide Ph Range ◽  
Ph Range ◽  
X Ray Absorption

AbstractThe speciation of antimony is strongly influenced by its oxidation state (V, III, 0, —III). Redox processes under anaerobic groundwater conditions may therefore greatly alter the environmental behaviour of Sb. Employing X-ray absorption and photoelectron spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not reduced further. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position otherwise occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, and at pH values >6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, at the mackinawite surface, Sb(V) is completely reduced across a wide pH range and within 1 h. The Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulphide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nano-particulate SbS3-like solid formed.

Synthesis and Structure of the Hexaethylcyclohexaarsoxane Complexes [ { M(CO)3} 2{cyclo-(C2H5AsO)6}], M = Cr, Mo, W

1993 ◽  
Vol 48 (8) ◽  
pp. 1069-1074 ◽  
Author(s):  
William S. Sheldrick ◽  
Thomas Häusler
Keyword(s):  
Molecular Structure ◽  
Structural Analysis ◽  
Equatorial Plane ◽  
Spectroscopic Data ◽  
Ring Expansion ◽  
X Ray ◽  
H Nmr ◽  
Ring Form ◽  
Nmr Data ◽  
Hexadentate Ligand

The hexaethylcyclohexaarsoxane complexes [{M(CO)3}2{cyclo-(C2H5AsO)6}], M = Cr, Mo, W, 2-4 have been prepared by the reaction of (C2H5AsO)n with the respective metal hexacarbonyl in toluene and characterized by their IR and NMR spectroscopic data. For 2 the molecular structure was established by X-ray structural analysis. The 12 atoms of the As6O6 ring form a flattened cuboctahedron in which the 6 oxygen atoms lie in the central equatorial plane. Cr(CO)3 groups are coordinated facially by the upper and lower three arsenic atoms. An approximately S6 symmetry is displayed by the Cr2As6O6 core. Average values of respectively 116.3 and 98.9° are observed for the As–O–As and O–As–O angles in the hexadentate ligand. The ΕΙ-MS and 1H NMR data for (C2H5AsO)n suggest that this alkylcycloarsoxane is present in solution as a mixture of species including trimers and tetramers so that a metal assisted ring expansion is required for the formation of 2-4.

Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts

1992 ◽  
Vol 57 (12) ◽  
pp. 2529-2538 ◽  
Author(s):  
Krasimir Ivanov ◽  
Penka Litcheva ◽  
Dimitar Klissurski
Keyword(s):  
Methanol Oxidation ◽  
Solution Concentration ◽  
Alkaline Media ◽  
Acidic Media ◽  
Chemical Methods ◽  
X Ray ◽  
Ph Values ◽  
Precipitate Composition

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

Synthesis and characterization of meso-to-meso directly linked porphyrin-diazaporphyrin triads

2018 ◽  
Vol 22 (09n10) ◽  
pp. 814-820
Author(s):  
Yingying Jia ◽  
Ling Xu ◽  
Bangshao Yin ◽  
Mingbo Zhou ◽  
Jianxin Song
Keyword(s):  
Nickel Complex ◽  
High Resolution Mass Spectrometry ◽  
Dihedral Angles ◽  
X Ray Diffraction ◽  
Extinction Coefficients ◽  
X Ray ◽  
H Nmr ◽  
First Time ◽  
Molar Extinction Coefficients

Beginning with 5,10,15-triarylporphyrin-nickel complex, five meso-to-meso directly linked porphyrin-diazaporphyrin triads were successfully prepared for the first time through a series of reactions including formylation via Vilsmeier–Haack reaction, condensation with pyrrole, bromination with [Formula: see text]-Bromosuccinimide (NBS), oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), metal-templated cyclization of dibromodipyrrin-metal complexes with NaN[Formula: see text] and demetalization. All these triads were comprehensively characterized by [Formula: see text]H NMR, high-resolution mass spectrometry and UV-vis absorption. In addition, the structure of compound 6Ni was unambiguously determined by X-ray diffraction analysis, which showed that the two dihedral angles are both 86.65 (4)[Formula: see text] between each mean plane of porphyrin and that of central diazaporphyrin The UV-vis absorption spectra disclosed that the longest wavelengths of Soret bands and Q bands for these triads were observed at 429 and 642 nm, respectively. In contrast to diazaporphyrin-porphyrin dyads, diazaporphyrin dimers and diazaporphyrin monomers reported previously the molar extinction coefficients, particularly for triad 8Ni are much higher.

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