Electrochemically induced transformations of heteropolyanions: new electroactive metal oxide films studied by the electrochemical quartz crystal microbalance

New oxide films have been electrodeposited from [P₂Mo₁₈O₆₂]⁶⁻ by potential cycling in mildly acidic aqueous media. To obtain an adherent and persistent film, it is necessary that more than six electrons/molecule be fixed on the framework of the heteropolyanion. The film is then studied in pure supporting electrolyte. In this medium, a remarkable current increase is observed during the potential cycling. Whether the film is deposited on a glassy carbon electrode or on the gold electrode of an electrochemical quartz crystal microbalance (EQCM), exactly the same steady current increase up to a maximum is obtained in cyclic voltammetric measurements. The EQCM reveals a steady mass increase during the continuous cycling of the film in the supporting electrolyte. This behaviour is interpreted as featuring an irreversible water and electrolyte intake into the film, up to a maximum, after which the phenomena observed during reduction and oxidation processes are taken as featuring intercalation/deintercalation, respectively. This behaviour is much the same as described in the literature for WO₃ and MoO₃ bronzes, except that the present films seem very stable and have shown no tendency to dissolve or deactivate. Received: 2 December 1998 / Accepted: 26 January 1999     

Conductivity of Phosphoric Acid, Sodium, Potassium, and Ammonium Phosphates in Dilute Aqueous Solutions from 278.15 K to 308.15 K

Precise conductivity measurements on aqueous solutions of phosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, diammonium hydrogen phosphate, sodium phosphate, and potassium phosphate were performed from 5 to 35°C. Data analysis was executed by the use of the Quint–Viallard equation for unsymmetrical electrolytes. Equations are given for the concentration dependence of electrolyte and single-ion conductivities at all temperatures.     

Novel rearrangements and formation of 2,5-dihydro-1,2,5-oxoniastannaboratolesvia methanolysis of zwitterionic η2-(alkyn-1-yl-borate)alkenyltin compounds

Organo-substituted 2,5-dihydro-1,2,5-oxoniastannaboratoles3 were prepared by methanolysis of zwitterionic ²-(alkyn-l-ylborate)alkenyltin compounds1. Analogously, the bis[²-(alkyn-l-yl-borate)alkenyltin derivative2 reacts with an excess of methanol to give a dimeric MeO-bridged 2,5-dihydro-1,2,5-oxoniastannaboratole (10a)₂. Various intermediates could be identified by NMR spectroscopy, and the molecular structure of(10a) ₂ was determined by X-ray analysis. The structures of several products of the methanolysis indicate that protolysis of an Sn-C=bond occurs first, followed by an MeO/alkenyl exchange reaction.Dedicated to the 100th Anniversary of A. N. Nesmeyanov's birth.Laboratorium für Anorganische Chemie, Universität Bayreuth, D-95440 Bayreuth, Germany Institut für Anorganische Chemie, Universität-GH Essen, Universitätsstr. 5–7, D-45117 Essen, Germany. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1185–1196, September, 1999.     

An improved synthesis of 3-deazaeytosine, 3-deazauracil, 3-deazacytidine,and 3-deazauridine

3-Dcazacytosine (4-amino-2-pyridone, 3 ), 3-doazauracil (4-hydroxy-2-pyridone, 5 ), 3-deaza-cytidine (4-amino-1-β-D-ribofuranosyl-2-pyridonc, 9 ), and 3-deazauridine (4-hydroxy-1-β-D-ribo-furanosyl-2-pyridone, 11 ) were prepared in high overall yields from 1-methoxy-1-buten-3-yne ( 1 ). Ethyl 3,5,5-triethoxy-3-pentenoate ( 2 ), obtained from acylatioti of 1 with diethyl carbonate and subsequent in situ conjugate addition of ethoxide, was cyelized with ammonia to provide 3 . Diazotization of 3 and subsequent in situ hydroxydediazotization afforded 5 . Nucleoside 9 was obtained from the stannic chloride-catalyzed condensation of bis-trimethylsilylated 3 and 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 7 ), followed by ammonolysis of the blocking groups. Diazotization of 9 and subsequent in situ hydroxydediazotization afforded nucleosidc 11 .     

Effect of bulky ligands on one-dimensional platinum compounds

Summary Diaminedithiocyanatoplatinum(II) complexes react with iodine in ethanolic suspension to yield diamagnetic compounds of empirical formula Pt(diamine)(SCN)₂I, which exhibit properties characteristic of one-dimensional materials. Incorporation of bulky substituents in the diamine ligand does not prevent the extended z-axis interaction responsible for these properties, in contrast to the effect of large ligands upon cooperative phenomena in Magnus' Green Salt analogues.Reprintsof this article are not available.The phase cooperative phenomena refers to magnetic and electronic properties that arise form the interaction between neihbouring metal in the solid state.     

Synthesis of imidazo[4,5-d]pyridazine nucleosides related to inosine

Several imidazo[4,5-d]pyridazine nucleosides which are structurally similar to inosine were synthesized. Anhydrous stannic chloride-catalyzed condensation of persilylated imidazo[4,5-d]-pyridazin-4(5H)one (1) and imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 16 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 3 ) provided (after sodium methoxide deblocking) 6-β-D-ribo furanosylimidazo[4,5-d]pyridazin-4(5H)one (5) and 3,6-di-(β-D-ribofuranosyI)imidazo[4,5-d]pyridazin-4-one ( 7 ); and 1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 19 ) and 1,5 or 6-di-(β-D-ribofuranosyl)imidazo[4,5-d ]pyridazine-4,7(5H or 6H)dione ( 21 ), respeeitvely. 4,7-Diehloro-1-β-D-ribofuranosylimidazo[4,5-d]pyridazine ( 12 ) and dimethyl 1-β-D-ribofuranosylimidazole-4,5-dicarboxylate ( 26 ), both prepared from stannic chloride-catalyzed ribosylations of the corresponding heterocycles, were converted in several steps to 3-β-D-ribo-furanosy limidazo[4,5-d]pyridazin-4(5H)one ( 14 ) and nucleosidc 19 , respectively. Acid-catalyzed isopropylidenation of mesomeric betaine 7 or nuclcoside 14 provided 3-(2,3-isopropylidene-β-D-ribofuranosyl)imidazo[4,5-d]pyrizin-4(5H)one ( 31 ). 1-β-D-Ribofuranosylimidazo[4,5-d]-pyridazine ( 29 ) was obtained in several steps from nueleoside 12 . The structure of the nucleosides was established by the use of carbon-13 and proton nmr.     

Struktur und Reaktivität eines Triazolobenzodiazepin/Oxalylchlorid-Addukts

Structure and Reactivity of a Triazolo-benzodiazepine/Oxalyl Chloride Adduct Reaction of oxalyl chloride with N, N-dimethyl-{8-chloro-6-(0-fluorophenyl)- 4H, 11 H-[1,2,4]triazolo [1,5-α] [1,4]benzodiazepine}-2-carboxamide ( 6a ), the syn-thesis of which is described, leads to the cyclic adduct N, N-dimethyl-{2,12,12-trichloro-13a-(0-fluorophenyl)-11-oxo-10,11,12,13a-tetrahydro-5H, 9H-[1,3]oxazolo [3,2-d] [1,2,4]triazolo [1,5-a] [1,4]benzodiazepine}-7-carboxamide ( 7a ). Upon thermolysis 7a is partly reconverted to the starting diazepine 6a via loss of the elements of oxalyl chloride. Reduction of 7a with sodium borohydride also yields 6a in addition to its dihydro derivative 9 . Energetic treatment of 7a with sodium methoxide leads to the unexpected methoxydiazepines 10a and 10b , and mild treatment of 7a with sodium methoxide to the stereoselective formation of the two precursors of 10 , namely the chloromethoxy derivative 11 and the dimethoxy derivative 12 . Epimerization of 11 followed by nucleophilic substitution gives a mixture of two dimethoxy compounds, 12 and its epimer 14 . The configurational assignments of these derivatives are based upon X-ray analysis of 12 . A possible pathway for this unexpected substitution reaction is proposed.