Katalytisch-kinetische bestimmung von katalase, kupfer, molybdän und jodid mit hilfe eines biamperostaten

Biamperometrically observable reactions may be evaluated by the “potentiostat”-method with the application of a current-to-voltage transducer. The catalase-catalyzed autodecomposition of hydrogen peroxide, the copper-catalyzed oxidation of iodide with peroxydisulfate, the molybdenum(VI)-catalyzed oxidation of iodide with hydrogen peroxide, and the iodide-catalyzed oxidation of arsenic(III) with cerium(IV) are used to illustrate this concept. The catalysts, catalase, copper(II), molybdenum(VI) and iodide, as well as azide as an inhibitor for catalase, can be determined in the p.p.b.-p.p.m. range.     

Coulometrische Erzeugung von Molybd?n(V)

Ohne Zusammenfassung     

Struktur und ausgewählte Reaktionen von ReCl4(PPh3)2

ReCl₄(PPh₃)₂ – Reactions and Structure The compounds ReCl₄(PPh₃)₂ and Re₂OCl₃(C₂H₅COO)₂(PPh₃)₂ resulting from the reaction of ReOCl₃(PPh₃)₂ with PPh₃ in boiling propionic acid and HCl atmosphere were characterized by their VIS-spectra and structural data. Ligand exchange reactions with acetylacetone gave ReCl₂(acac)₂ as well as ReCl₂(acac)(PPh₃)₂. Crystallographic data see “Inhaltsübersicht”.     

Metallkomplexe mit anionischen Liganden von Elementen der 4. Hauptgruppe. VIII. Pentacarbonyl-trihalogenstannido-metallat(O)-Komplexe von chrom,molybdän und wolfram mit fluor- und jodhaltigen stannidliganden

Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C₆H₅)₄][SnF₃] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)₅SnF₃]^? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)₅THF only one pure triiodostannidometalate(O) Complex, [N(C₂H₅)₄][Cr(CO)₅SnJ₃], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)₅SnClX₂]^? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX₂-insertion reactions of the [M(CO)₅Cl]^? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes.     

Zur polarographischen Reduktion von Molybdän(VI) und Molybdän(V) in Gegenwart von Citronensäure

According to the ratio of citric acid to molybdenum different citratomolybdenum(VI) complexes exist at pH <2. Only one citratomolybdenum(VI) complex exists in solutions with a great excess of citric acid (20:1). In such solutions the polarographic reduction of Mo^VI proceeds in two waves: First Mo^VI → M^V, then Mo^V → Mo^IV, which disproportionates into Mo^V and Mo^III however. Furthermore, it is possible that the Mo^IV reacts with Mo^VI forming Mo^V, so that also a catalytic character can be attributed to the second wave besides a kinetic one.     

Synthese,Struktur und Reaktivität von Bis(dialkylamino)diphosphanen

Synthesis, Structure, and Reactivity of Bis(dialkylamino)diphosphines Starting with the aminochlorophosphines ⁱPr₂N? PCl₂ 1 and (ⁱPr₂N)₂P? Cl 2 , the synthesis of some new functionalized aminophosphines (ⁱPr₂N)₂P? SiMe₃ 3a , (ⁱPr₂N)₂P? SnMe₃ 3b , (ⁱPr₂N)(DMP)P? Cl 4 , ⁱPr₂N? P(SiMe₃)₂ 5 and ⁱPr₂N? P(SiMe₃)Cl 6 is reported. Reactions of 2 with different phosphides yield the aminodiphosphines (ⁱPr₂N)₂P? P(SiMe₃)₂ 7a , (ⁱPr₂N)₂P? P(SiMe₂^tBu)₂ 7b , (ⁱPr₂N)₂P? PPh₂ 8 and (ⁱPr₂N)₂P? PH₂ 9 . The phosphines 3a/b react with halogenophosphines to the aminohalogenodiphosphines (ⁱPr₂N)₂P? PCl₂ 10 , (ⁱPr₂N)₂P? P^tBuCl 11 and (ⁱPr₂N)₂P? P(NⁱPr₂)Cl 12 . The ambivalente aminophosphine 6 gives the aminotrichlorodiphosphine Cl(ⁱPr₂N)P? PCl₂ 13 after condensation with PCl₃, while the reactions with the corresponding lithiumphosphides yield the aminosilyldiphosphines (ⁱPr₂N)(SiMe₃)P? P(SiMe₃)₂ 14a and (ⁱPr₂N)(SiMe₃)P? P(SiMe₂^tBu)₂ 14b . The aminochlorophosphines 2/4 are reductively coupled with magnesium leading to the symmetrically substituted tetraaminodiphosphines (ⁱPr₂N)₂P? P(ⁱPr₂N)₂ 15a and DMP(ⁱPr₂N)P? P(ⁱPr₂N)DMP 15b . The functionalized aminosilyldiphosphine 7a is treated with methanol to yield the diphosphine (ⁱPr₂N)₂P? PH(SiMe₃) 16 and gives the lithium phosphinophosphide (ⁱPr₂N)₂P? PLi(SiMe₃) 17 after metallation with n-BuLi. The compounds are characterized by their NMR and mass spectra and the ³¹P-NMR values of the diphosphines are discussed according to their substituents. The crystal structures of 7b, 8 and 15b showing significantly differing conformations are presented.     

Synthese,Struktur und Phasenumwandlung von Se4(MoOCl4)2

Synthesis, Crystal Structure, and Phase Transition of Se₄(MoOCl₄)₂ Dark green, very air sensitive crystals of Se₄(MoOCl₄)₂ are formed from selenium and MoOCl₄ at 190°C in a sealed, evacuated glass ampoule in quantitative yield. The structure is built of nearly square planar Se₄²⁺ ions and centrosymmetric dimeric MoOCl₄^? ions which are linked by bridging Cl atoms. At ?21°C Se₄(MoOCl₄)₂ undergoes a reversible solid state phase transition of first order. Structure determinations at ?70°C and 23°C show that during the phase transition the structures of the ions remain unchanged, while the orientations of the ions with respect to each other change in such a way that in the low temperature form the Se₄²⁺ ions obtain a higher coordination number by Cl and O atoms of neighboring MoOCl₄^? ions.     

Kupferkomplexe von Bisamiden: Struktur und Stabilität I

Complex formation between Cu²⁺ and several ligands, each containing two amino and two amide groups, has been studied potentiometrically and spectrophotometrically. A digital computer was used to determine the composition of the complex species formed and to calculate their stability constants. N,N′-diglycyl-1, 2-diaminoethane and its homologues form 5-, 6-, 7-, 8- and 9-membered rings between the two amide groups, respectively. No tendency towards formation of binuclear species has been observed.