Darstellung und Struktur von Tetrafluoro(η5-pentamethylcyclopentadienyl)niob und Tetrafluoro(η5-cyclopentadienyl)niob

Preparation and Structure of Tetrafluoro(η⁵-pentamethylcyclopentadienyl) Niobium and Tetrafluoro(η⁵-cyclopentadienyl) Niobium A facile preparation method for (η⁵-C₅Me₅)NbF₄ 3 and (η⁵-C₅H₅)NbF₄ 4 is reported by using AsF₃ as a fluorinating agent. Single crystals obtained from AsF₃ contain the solvent molecule as well as HF. The composition of the crystal is [(η⁵-C₅Me₅)NbF₄(AsF₃)₂]₂ · [(η⁵-C₅Me₅)NbF₄(HF)AsF₃]₂ 5 . The X-ray crystal structure of 5 will be reported. 5 crystallizes triclinic with one furmula in the space group P1 and lattice constants a = 843.1(4), b = 1154.9(6), c = 1910.2(10) pm, α = 91.68(3)°, β = 99.30(3)°, γ = 104.44(2)°.     

Heterobimetallische phosphanido-verbrückte Zweikern-Komplexe - Synthese von cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6−iPr3C6H2)}2M(CO)4] (RMe,MCr,Mo; RH,MMo)

Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C₅H₄R)₂Zr{PH(2,4,6-ⁱPr₃C₆H₂)}₂] (R?Me, H) react with [(NBD)M(CO)₄] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C₅H₅)₂Zr{PH(2,4,6-^tBu₃ C₆H₂)}₂] and [Pt(PPh₃)₄]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS₂, (NO)BF₄, Me₃NO or PH(2,4,6-Me₃C₆H₂)₂. With Et₂AlH or PhC?CH decomposition of 3 was observed.     

Ein alternativer Weg zur Darstellung von Bi2Sr2CaCu2Ox,YBa2Cu3O7−δ, und YBa2Cu3−xMxO7−δ (M  Ni,Ag und x ≤ 33 Mol%)

An Alternative Method for Preparation of Bi₂Sr₂CaCu₃O_x, YBa₂Cu₃O_7?δ, and YBa₂Cu_3?xM_xO_7?δ (M ? Ni, Ag and x ≤ 33 Mol%) Oxidation of quenched melts of metals in a well defined argon/oxygen atmosphere has been found as an alternative method to prepare hight purity samples of Bi₂Sr₂CaCu₂O_x without Pb-stabilization. A special equipment for the oxidation of powder samples will be described. By our new method it is also possible to prepare YBa₂Cu₃O_7?δ and derivatives of this compound, where Cu is substituted by high amounts of Ni or Ag.