Showing papers in "Inorganic Chemistry in 1985"

Reaction of superoxide with nitric oxide to form peroxonitrite in alkaline aqueous solution

Abstract: Although aqueous superoxide often acts as a one-electron reductant or less frequently as an oxidant, it rarely undergoes covalent bond formation with simple organic or inorganic compounds in water, perhaps owing to its poor nucleophilicity in this solvent. In this communication it is shown, however, that superoxide can react with nitric oxide to form the peroxionitrite anion in deaerated aqueous solutions at pH 12-13: O/sub 2//sup -/ + NO = /sup -/OONO. This reaction represents one of the few examples of a radical-radical coupling of O/sub 2//sup -/ with another odd-electron species to form a diamagnetic product. The reaction also may be of significance in natural waters or prove useful for trapping and measuring low levels of superoxide in aqueous systems. 13 references, 2 figures, 1 table.

Light-induced excited-spin-state trapping in iron(II) spin-crossover systems. Optical spectroscopic and magnetic susceptibility study

Abstract: Single-crystal optical absorption spectra of the iron(I1) sph-crossover compounds [Fe(pt~)~]@F~), (ptz = 1-propyltetrazole) and [Fe(2-pi~)~]Cl,.EtOH (2-pic = 2-(aminomethy1)pyridine) have been.measured between room temperature and 8 K. The wellestablished thermally induced spin transition high spin (?,& + low spin (lAIg) as well as the recently discovered phenomenon of 'light-induced excited-spin-state trapping (LIWT)" is followed and analyzed. A kinetic study by optical spectroscopy of the relaxation from the light-induced high-spin (HS) state to the low-spin (LS) state has been carried out for [Fe(ptz),](BF,), in the temperature range 53-61 K. The magnetic susceptibility of the light-induced HS state of this compound has also been measured.

Kinetics and mechanism of ozone decomposition in basic aqueous solution

Abstract: L'etape d'initiation serait O 3 +OH − →HO 2 − +O 2 qui correspond a un processus de transfert de 2 electrons

Copper(II) and nickel(II) complexes of unsymmetrical tetradentate Schiff base ligands

Abstract: Preparation de bases de Schiff tetradentees a partir de chloro-5 hydroxy-2 benzophenone, diamino-1,2 benzene et salicylaldehydes substitues. Synthese des complexes de Cu et Ni. Structures cristallines

Synthesis, structure, and spectroscopic and magnetic properties of lutetium(III) phthalocyanine derivatives: LuPc2.CH2Cl2 and [LuPc(OAc)(H2O)2].H2O.2CH3OH

Abstract: The bis(phthalocyaninato)lutetium(III) derivative LuPc/sub 2/ x CH/sub 2/Cl/sub 2/ (1, LuC/sub 65/H/sub 34/N/sub 16/Cl/sub 2/) and the (phthalocyaninato)lutetium(III) complex (LuPc(OAc)(H/sub 2/O)/sub 2/) x H/sub 2/O x 2CH/sub 3/OH (2, LuC/sub 36/H/sub 33/N/sub 8/O/sub 7/) were synthesized in boiling 1-hexanol with use of lutetium(III) acetate and 1,2-dicyanobenzene in the presence of 1,8-diazabicyclo(5.4.0)undec-7-ene and purified by chromatography. The visible spectroscopic properties are reported for both complexes. 1 crystallizes in the orthorhombic system with a = 28.242 (9) A, b = 22.877 (8) A, c = 8.050 (4) A, Z = 4, and space group Pnma. 2 belongs to the monoclinic system with a = 12.033 (3) A, b = 20.807 (6) A, c = 14.011 (3) A, ..beta.. = 95.34 (2)/sup 0/, space group P2/sub 1//n, and Z = 4. 1 is a sandwich type complex in which the lutetium atom is eightfold coordinated by the isoindole nitrogens (N/sub iso/) of two staggered phthalocyanine rings. 28 references, 5 figures, 6 tables.

Bimetallic reactivity. Synthesis of bimetallic complexes containing a bis(phosphino)pyrazole ligand

Abstract: Preparation du coordinat (L') qui est tetradente. Isolement des complexes [M 2 (L')(X)L 2 ] (M=Pd, Rh ou Ir, X=Cl ou PPh 2 et L=CO) et [M 2 (L')L 4 ] + (2L=π-allyl ou diene)

Steric and electronic control of iron porphyrin catalyzed hydrocarbon oxidations

Abstract: The yields and product distributions in the oxidation of hydrocarbons (cyclohexane, n-pentane, n-octane, methylcyclohexane, tert-butylcyclohexane, and ethylbenzene), using substituted iron tetraphenylporphyrins and iodosobenzene, are shown to be markedly affected by nature and location of phenyl ring substituents. These substrates were used to measure the activity, regioselectivity, substrate selectivity, and stereoselectivity of the substituted iron porphyrin catalysts. Higher yields are observed with iron porphyrins having bulky substituents near the iron center. Kinetics measurements and concentration studies show that these substituents improve lifetimes by hindering the catalyst's bimolecular self-destruction. Higher yields are also observed with electron-withdrawing substituents. A new iron fluoro-pocket porphyrin shows higher activity due to this electronic effect. Substrate and regioselectivity are also influenced by steric and electronic effects of the iron porphyrin's phenyl ring substituents. Bulky porphyrins also affect the stereoselectivity at the 2-, 3-, and 4-positions in tert-butylcyclohexane oxidation. A mechanism supported by kinetic modeling studies is proposed for the oxidation reactions. 48 references, 14 figures, 5 tables.

Synthesis, structural characterization, and electrochemistry of [1]metallocenophane complexes, [Si(alkyl)2(C5H4)2]MCl2, M = Ti, Zr

Abstract: A series of modified metallocene dichloride compounds, (SiR/sub 2/(C/sub 5/H/sub 4/)/sub 2/)MCl/sub 2/ (M = Ti, R = CH/sub 3/; M = Zr, R = CH/sub 3/, C/sub 2/H/sub 5/, n-C/sub 3/H/sub 7/), have been prepared to evaluate the presence of a dialkylsilyl bridge on their electrochemical behavior. The compounds have been characterized by elemental analysis and /sup 1/H and /sup 13/C NMR, and the molecular structures of (Si(CH/sub 3/)/sub 2/(C/sub 5/H/sub 4/)/sub 2/)MCl/sub 2/, M = Ti, Zr, have been determined by X-ray diffraction methods. The /sup 13/C NMR resonance of the bridgehead carbons is consistently located substantially upfield from the corresponding resonances for the proximal and distal carbons of the rings in these compounds. Cyclic voltammetric measurements have shown that these (1)metallocenophane dichlorides exhibit only one one-electron reversible reduction in THF within a scan range of +1.0 to -3.0 V vs. SCE. Complementary EPR studies were conducted to identify and monitor the stability of the paramagnetic species generated during the electrochemical reduction of (Si(CH/sub 3/)/sub 2/(C/sub 5/H/sub 4/)/sub 2/)TiCl/sub 2/ and the sodium naphthalide reduction of (Si(CH/sub 3/)/sub 2/(C/sub 5/H/sub 4/)/sub 2/)MCl/sub 2/, M = Ti, Zr. These reduction processes proceed similarly with the formation of only onemore » paramagnetic product, (Si(CH/sub 3/)/sub 2/(C/sub 5/H/sub 4/)/sub 2/)MCl/sub 2//sup -/. The compounds (Si(CH/sub 3/)/sub 2/(C/sub 5/H/sub 4/)/sub 2/)MCl/sub 2/, M = Ti, Zr, similarly crystallize in a monoclinic unit cell of C2/c symmetry with the following refined lattice parameters: for M = Ti, a = 13.309 (5) A, b = 9.871 (2) a, c = 13.337 (4) A, ..beta.. = 132.79 (1)/sup 0/, V = 1285.8 (7) A/sup 3/, and rho/sub calcd/ = 1.576 g/cm/sup 3/; for M = Zr, a = 13.391 (3) A, b = 9.965 (2) A, c = 10.922 (3) A, ..beta.. = 113.37 (2) A, V = 1337.8 (5) A/sup 3/, and rho/sub calcd/ = 1.730 g/cm/sup 3/. 44 references, 6 figures, 7 tables.« less

Further insight into magnetostructural correlations in binuclear copper(II) species related to methemocyanin: x-ray crystal structure of 1,2-.mu.-nitrito complex

Abstract: Determination de la structure de [Cu 2 (L-Et)(NO 2 )] [ClO 4 ] avec HL-Et=N,N,N'N'-tetrakis-([ethyl-1 benzimidazolyl]-2) hydroxy-2 diamino-1,3 propane

Tunable interaction in (.mu.-oxamido)copper(II) binuclear complexes

Abstract: Preparation des 3 complexes [Cu(oxpn)Cu(bpy)](ClO 4 ) 2 , [Cu(oxpn)Cu(petdien)](ClO 4 ) 2 et [Cu(oxpn)Cu(pmedien)](ClO 4 ) 2 et determination structurale des 2 premieres. Mesures des susceptibilites magnetiques, spectre RPE

Binuclear and polymeric gold(I) complexes

Abstract: Calculs par la methode de Huckel generalisee sur [Au 2 (S 2 PH 2 ) 2 ] 2 et [Au 2 (S 2 PH 2 ) 2 ] n : structure electronique, conformation

Cobalt(I) porphyrin catalysts of hydrogen production from water

Abstract: Cobalt complexes of three water-soluble porphyrins have been examined as catalysts of H/sub 2/O reduction to H/sub 2/. They have been shown to catalyze H/sub 2/ production via controlled-potential electrolysis (-0.95 V vs. SCE at Hg-pool electrode; 0.1 M trifluoroacetic acid) at rates approximately 10-fold greater than background and with nearly 100% current efficiency. Reversible cyclic voltammograms were observed in dry Me/sub 2/SO, with Co(III)/Co(II) and Co(II)/Co(I) potentials near their expected values. Addition of water (0.5-2%) increased the cathodic peak and decreased the anodic peak at the Co(II)/Co(I) couple, consistent with electrocatalytic H/sub 2/O reduction. In aqueous buffers, catalytic currents were observed for CoTMPyP, which increased with decreasing pH, but at a rate less than expected, due to porphyrin adsorption. Adsorption was more pronounced for CoTMAP, which showed no catalytic current except at very low pH. The rate of Co/sup I/TMAP reaction with H/sub 2/O, however, is extremely fast as shown by spectrophotometry in dry acetonitrile; a lower limit for the Co(I)-H/sub 2/O reaction rate constant was estimated to be approximately 10/sup 4/ M/sup -1/s/sup -1/. Co(I) reactivity and cobalt hydride stability are discussed in comparison with the reactivity and stability of related compounds.

Synthesis and molecular structure of oxochromium(V) cations. Coordination with donor ligands

Abstract: Preparation d'une serie de complexes et etude structurale du triflate de N,N'-ethylenebis(salicylidene aminato) oxochrome et du compose d'addition forme avec l'oxyde de pyridine

Synthetic control of excited states. Nonchromophoric ligand variations in polypyridyl complexes of osmium (II)

Abstract: Two themes are explored with regard to the properties of the metal to ligand charge-transfer (MLCT) excited states of Os(II). For a series of Os(II) complexes it is shown that the MLCT excited states undergo facile oxidative or reductive quenching. Excited-state redox potentials have been estimated by both kinetic quenching and spectroscopic techniques for excited-state oxidative couples and excited-state reductive couples. The second theme, the manipulation of excited-state properties by synthetic changes, follows from a consideration of these factors that dictate excited-state redox potentials. It is shown that in the series (phen)OsL/sub 4//sup 2 +/ (L = pyridine, CH/sub 3/CN, PR/sub 3/, AsR/sub 3/, ... and phen = 1,10-phenanthroline) where the metal-ligand basis for the MLCT chromophore remains the same and variations are made in the nonchromophoric ligand, emission energies, excited-state redox potentials, and radiative and nonradiative rate constants all vary systematically with the potential of the ground-state Os(III/II) couple. The results show that it is possible through synthetic changes to control excited-state properties in a systematical way. 37 references, 6 figures, 5 tables.

Dimerization of cobalt(II) tetrasulfonated phthalocyanine in water and aqueous alcoholic solutions

Abstract: : Metal complexes of tetrasulfonated phthalocyanine (TSPC) are of interest as oxidation and hydrolysis catalysts for thioethers and organophosphonates. Since metal TSPC complexes aggregate in aqueous solution, it was necessary to determine the dimerization constant as a prerequisite to establishing the efficacy of the monomeric Cobalt (II) TSPC (CoTSPC) complex as a catalyst. Since these potential catalysts will be used in mixed solvents to dissolve thioethers, the aggregation of CoTSPC was measured in alcohol-water solutions at various temperatures. This study uses a nonlinear, least-squares program to compute best-fit molar absorbances for monomers and dimers simultaneously. In addition, the monomer-dimer equilibrium is investigateed over a wide temperature range, 5-75 C, in water to determine if the standard enthalpy of formation varies with temperature. It was found that the enthalpy was temperature-dependent, possessing a constant value of Delta C subscript p deg. of 0.1 kcal/mole-K. It was also shown that earlier investigators deduced dimerization constants that were smaller than the ones reported in this investigation. We feel this was caused by the presence of higher aggregates and unwarranted assumptions in the method to estimate the dimerization constant. It is also shown that the dye, CoTSPC, behaves as typical non-aqueous solute, and that hydrophobic bonding is not involved in the formation of the dimer. Originator supplied keywords include: Cobalt (II) complexes; Monomer-dimer equilibria; Thermodynamics; Methanol-water solution; Dyestuffs; Tetrasulfonated and Phtalocyanine.

Layered hydrous titanium dioxide: potassium ion exchange and structural characterization

Abstract: which is obtained from potassium tetratitanate (K2Ti409), has been studied by examining the titration curve in relation to the structural change of the material. Structural characterization has also been performed for layered hydrous titanium dioxide and its potassium ion exchanged phases. The material has almost the same sheet structure of [Ti40$In as that of potassium tetratitanate, in which hydronium ions and hydroxylated protons are situated as exchangeable ones. The ion exchange proceeds stepwise through four stages (0-25, 25-50, 50-70, and 70-98% conversion), indicating that potassium ions replace the exchangeable protons one by one. During the process four solid phases appeared with different interlayer distances and cation/water contents: one-fourth-exchanged phase, &, SH1,5Ti409.0.6H20; half-exchanged phase, KHTi409.0.5H20; approximately three-fourths-exchanged phase, K1.4H,,6Ti409.1 .2H20 and fully exchanged phase, K2Ti409.2.2H20. The study of the unit cell dimensions of these phases indicates that the ion exchange takes place accompanied by a contraction/expansion of interlayer distances and a shift of adjacent sheets in relation to each other along the c axis. A lattice type change occurred during the process, which is considered to be due to the arrangement of potassium ions and/or water molecules incorporated in the interlayer space. A structural model is proposed for the fully exchanged phase in which interlayered potassium ions and water molecules occupy the sites arranged' in a double row and shifted above and below the levels at y = 0 and Models for the other ion-exchanged phases are also proposed to interpret the ion-exchange mechanism from a structural aspect.

Magic numbers in polygonal and polyhedral clusters

Abstract: Certain values for the nuclearity of clusters tend to occur more frequently than others. This paper gives a mathematical derivation of the preferred values of nuclearity (the “magic numbers”) corresponding to various symmetrical, close-packed polygons (in two dimensions) and polyhedra (in three dimensions). Simple general formulas are obtained for the numbers of atoms in these clusters. Explicit coordinates are given for the atoms. Application of these atom-counting results to electron counting of close-packed high-nuclearity metal clusters is illustrated.

Inter- vs. intramolecular C-H activation: a C-H-Ir bridge in [IrH2(8-methylquinoline)L2]BF4 and a C-H+M→C-M-H reaction trajectory

Abstract: Determination de la structure cristalline du complexe [IrH 2 (methyl-8 quinoleine)(PPh 3 ) 2 ]SbF 6 . Developpement de la mesure de la force de l'interaction pont et utilisation pour systematiser les donnees sur 17 structures apparentees

Coordination chemistry of the bimacrocyclic, potentially binucleating ligand 1,2-bis(1,4,7-triaza-1-cyclononyl)ethane (dtne). Electrochemistry of its first transition series metal(II,III) complexes. Characterization of the new hemerythrin model complex [Fe2(dtne)(.mu.-O)(.mu.-CH3CO2)2]Br2.H2O

Abstract: Preparation du coordinat dtne et des complexes [M(dtne)] 3+ avec M=Cr, Fe, Co et Ni, et [M'(dtne)] 2+ avec M'=Mn, Ni, Cu et Zn sous forme de bromure perchlorate et hexafluorophosphate. Mesure des moments magnetiques effectifs et des spectres electroniques. Determination par voltammetrie cyclique des couples redox de [M(dtne)] 3+/2+ avec M=Cr, Mn, Fe, Co et Ni. Donnee, aussi, sur le complexe [Fe 2 (dtne)(μ-O)(μ-CH 3 CO 2 ) 2 ]Br 2 •H 2 O

Electronic spectra of phthalocyanine radical anions and cations

Abstract: : The oxidation and reduction of metal phthalocyanines give rise to at least six oxidation states whose electronic spectra are rationalized in some depth in terms of SCF energies, Coulomb and exchange integrals. It is shown that a single set of parameters can reproduce the Q band energies moderately well. Further this same set of energies can reproduce differences in electrochemical potentials observed within this redox set. The pattern of variation in the Q band energies (and in their number) now provides a means for identifying whether it is the metal or the phthalocyanine ligand which is reduced upon addition of an electron to the system.

A further example of a dinuclear copper(II) complex involving monoatomic acetate bridges. Synthesis, crystal structure, and spectroscopic and magnetic properties of bis(.mu.-acetato)bis(7-amino-4-methyl-5-aza-3-hepten-2-onato(1-))dicopper(II)

Abstract: (C 19 H 16 N 2 O 3 Cu) 2 cristallise dans P1 avec Z=1; affinement jusqu'a R=0,025. Spectre RPE. Susceptibilite magnetique

15N and 195Pt NMR spectra of platinum ammine complexes: trans- and cis-influence series based on 195Pt-15N coupling constants and 15N chemical shifts

Abstract: 195Pt and 15N NMR spectra have been obtained for the series of platinum(II) complexes Pt(15NH3)3Zn+, cis-Pt(15NH3)2Z2m+, and cis-Pt(15NH3)2YZm+ (Z, Y are neutral or anionic ligands) and for the platinum(IV) complexes derived from them by peroxide oxidation, mer-Pt(15NH3)3Z(OH)2 n+ and Pt(15NH3)2Z2(OH)2 m+. From the spectra of the triammineplatinum(II) complexes, the effects on δN and 1J(Pt-N) trans and cis to Z, and on δPt, of replacing one of the ammine ligands of Pt(15NH3)4 2+ by Z were measured. With the assumption that the effects of replacing two ammine ligands are additive, the NMR parameters for diammineplatinum(II) complexes were calculated. Agreement with experimental values was good overall. NMR data for the platinum(IV) complexes were treated similarly, again with good agreement between calculated and experimental values for the diammine complexes. The influence of different ligands Z on the NMR parameters for the two different oxidation states, while generally similar, did show some consistent differences in detail. The influences of the halide ions on δPt, and on δN and J(Pt-N) trans to Z, were greater for platinum(IV) relative to platinum(II). For the series Pt(15NH3)3Zn+, results are consistent with previous generalizations, that changes in δPt mainly depend on the influence of Z on Pt 5d orbitale (through involvement in the Pt-Z σ-bond and through splitting of the d-orbital energy levels) and that changes in J(Pt-N) trans to Z depend mainly on variations in the Pt 6s contribution to the Pt-N bond. δN trans to Z shows an inverse linear correlation with δPt. Cis influences on δN and J(Pt-N) are smaller than trans influences but are still significant.