IrO2/SnO2 electrodes: prepared by sol-gel process and their electrocatalytic for pyrocatechol

IrO2/SnO2 (10%:90%, molar ratio) electrodes (ITEs) were prepared by the sol-gel method as an alternative to the electrode-position and thermal decomposition process. The electrodes were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). From the results of XRD, oxide films prepared at low temperature were in amorphous state, while hydrous IrO2 crystal and cassiterite phase SnO2 were formed at 300 degreesC or even to 500 degreesC. The highly porous structure was confirmed by AFM. The electrochemical experiments demonstrated that the sol-gel method made the ITEs having a fast electron transfer process with good stability and the optimal preparation temperature was 400 degreesC for the highest electroactivity. Furthermore, the electrocatalysis of pyrocatechol on the electrodes was investigated. A quasi-reversible process occurred and a linear range over three orders magnitude (1 x 10(-2) - 10 mM) was obtained by differential pulse voltammetry (DPV). Meanwhile the detection limit of pyrocatechol was 5 x 10(-3) mM. This study indicated that the sol-gel method was an appropriate route to prepare the IrO2/SnO2 electrodes for the electrocatalytic of pyrocatechol.

Syntheses and crystal structures of mononuclear rhodium hydrido complexes from the reactions of [Rh(H)(2)(PPh3)(2)(EtOH)(2)]ClO4 with various nitrogen ligands

Reactions of the Rh hydrido complex [Rh(H)(2)(PPh3)(2)(EtOH)(2)]ClO4 (1) With nitrogen ligands such as 2-(4-thiazolyl)benzimidazole (tbz). pyridazine (pdz), imidazole (im) and pyrimidine (pmd) in CH,Cl, afforded Various mononuclear Rh hydrido complexes, [Rh(H)(2)(PPh3)(2)(tbz)]CIO4 (2), [Rh(H)(2)(PPh3)(2)(pdZ)(2)]ClO(4)(.)2CH(2)Cl(2) (3). [Rh(H)Cl(PPh3)(2)(pdz)(2)](ClO4CH2Cl2)-C-. (4). [Rh(H)(2)(PPh3)(2)(im)(2)]ClO(4)(.)2CH(2)Cl(2) (5). [Rh(H)Cl(PPh3)(2)(im)(2)](ClO4CH2Cl2)-C-. (6). [Rh(H)(2)(PPh3)(2)(pmd)(2)](ClO4CH2Cl2)-C-. (7) and the Rh non-hydrido complex [RhCl2(pmd)(4)]ClO4 (8). The Rh complexes 2. 3, 5 and 6 were crystallographically characterized. The formation process was monitored by H-1 NMR and UV-Vis spectra. In all the Rh hydrido complexes, the Rh atom is coordinated by two PPh3. ligands in trans-positions and two nitrogen ligands in the cis-positions. The remaining sites Lire occupied by one or two hydride atoms to form a saturated 18-electron framework in a slightly distorted octahedral geometry. For complex 2 an appreciable inter-molecular pi interaction is observed between planes of tbz and PPh3 ligands, while an intra-molecular hydrogen bonding interaction between C-H and Cl atoms is found in complex 6.

Pentamethylcyclopentadienyl halfsandwich rhodium complexes containing 1,1 '-ferrocene dichalcogenido chelate ligands

The heterobimetallic complexes Cp * Rh(CN Bu-t)(EC5H4)(2)Fe [E = S(2),Se(3), Te(4)] have been synthesized by the reaction of halfsandwich rhodium complex Cp * Rh(CNtBu) Cl-2 with Fe(C5H4ELi)(2). 2THF. Oxidation of 2,3 by AgBF4 to give ferrocenium - type salts [Cp * Rh(CNtBu) (EC5H4)(2)Fe] (+) [BF4] (-) [E = S(5),Se(6)] also occurs readily. The new complexes have been characterized by MS IR, H-1 and C-13 NMR spectroscopy and elemental analysis.

Synthesis and characterization of polynuclear half-sandwich lanthanoid complexes [Na(THF)(6)](2)[(Cp6Sm6Se13)-Sm-t] and [Li(LHF4](2)[Cp6Nd6Se13]

The half-sandwich tert-butyl cyclopentadienyl lanthanoid complexes {[Cp ' Ln(THF)](2)(mu (2)-Cl)(2)(mu (3)-Cl)(3)Na(THF)}(n) [Cp ' = eta (5)-' BuC5H4; Ln = Nd (1a), Sm (1b), Gd (1c), Yb (1d)] are prepared by the reaction of anhydrous lanthanoid trichloride, LnCl(3), with NaCp ' in THF solution. Complex 1b reacts with Na2Se5 to give hexanuclear samarium polyselenide complexes [Na(THF)(6)](2)[Cp-6' SM6(mu (6)-Se)(mu -Se-2)(6)] (2). An analogous cyclopentadienyl neodymium polyselenide complex [Li(THF)(4)](2)[Cp6Nd6(mu (6)-Se)(mu -Se-2)(6)] (3) is synthesized by the reaction of [CpNdCl2. 2LiCl . 5THF] with Na2Se5 in THF solution. The molecular structures of 1a and 2 were determined by X-ray crystal structure analysis. Complex 2 contains an interstitial selenium atom which is coordinated with six samarium atoms. (C) 2001 Elsevier Science BN. All rights reserved.

16-and 18-electron Cp*Rh complexes with 1,2-dicarba-closo-dodecabofane(12)-1,2-dichalcogenolato ligands, as studied by multinuclear magnetic resonance

The reaction of [Cp*RhCl2](2) 1 with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate (a) and -diselenolate (b) afforded the 16-electron rhodium(III) half-sandwich complexes Cp*Rh[E2C2(B10H10)] [E=S (3a), Se (3b)]. The 18-electron trimethylphosphane rhodium(III) half-sandwiches Cp*Rh(PMe3)[E2C2(B10H10)] 4a-c were prepared from the reaction of Cp*RhCl2(PMe3) 2 with the same dichalcogenolates, including the ditelluride (c). The complexes 4a,b could also be obtained from the reaction of 3a,b with trimethylphosphane. The molecular geometry of 4b was determined by X-ray structural analysis. The 16-electron complexes 3 an monomeric in solution as shown by multinuclear magnetic resonance (H-1-, B-11-, C-13-, P-31- Se-77-, Rh-103-, Te-125-NMR). also in comparison with the data for the trimethylphosphane analogues 4a-c and for 6a in which the rhodium bears the eta(5)-1,3-C5H3 Bu-t(2) ligand. The Rh-103 nuclear shielding is reduced by 831 ppm (3a) and 1114 ppm (3b) with respect to the 18-electron complexes 4a,b. Similarly, the Se-77 nuclear shielding in 3b is reduced by 676.4 ppm with respect to that in 4b. (C) 1999 Elsevier Science S.A. All rights reserved.

Synthesis and x-ray structure of a highly symmetrical selenium-centered hexanuclear neodymium complex, [(Cp6Nd6Se13)-Nd-t](-) (Cp-t=eta(5)-(BuC5H4)-C-t)

The half-sandwich tert-buthylcyclopentadienyl neodymium complex [(CpNdCl2)-Nd-t(THF)(2)](2) (1) reacts with Na2Se5 to give organoneodymium polyselenide complex [Na(THF)(6)][(Cp6Nd6)-Nd-t(mu(6)-Se)(mu(2)-Se-2)(6)] (2) which has been characterized by X-ray crystallography.

ELECTROCATALYTIC REDUCTION OF DIOXYGEN BY AN ELECTROCHEMICALLY POLYMERIZED FLAVIN ADENINE-DINUCLEOTIDE FILM

An electrochemically polymerized flavin adenine dinucleotide (FAD) film electrode is reported for the first time. The polymerized film was prepared by a two-step method. The electrocatalytic reduction of dioxygen at a glassy carbon electrode (GCE) modifie

STUDIES ON THE REACTIONS OF TRANSITION-METAL HYDRIDES WITH HETEROCUMULENES .6. REACTION OF CP2ZR(H)CL WITH RNCS (R=C6H5, 2-C10H7, C-C6H11 AND N-C4H9)

The novel NS-containing zirconacycle complexes Cp2ZrCl[SC(H)NR] (1a, R = C6H5; 1b, R = 2-C10H7; 1c, R= C-C6H11; 1d; R = n-C4H9) were obtained by insertion reactions of Cp2Zr(H)Cl with RNCS. 1(a-d) could react further with Cp2Zr(H)Cl to yield a sulphur-bridging compleX (Cp2ZrCl)2S (2) and a Schiff base RN=CH2. The crystal structure of la has been determined by X-ray analysis.