Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. 55. Darstellung und Eigenschaften von Niobocenium- und Tantalocenium-Salzen – Kristall- und Molekülstruktur von [(C5H5)2NbCl2][BF4] · CH3CN

Contributions to the Chemistry of Organo Transition Metal Compounds. 55. Preparation and Properties of Niobocenium and Tantalocenium Salts — Crystal and Molecular Structure of (C₅H₅)₂NbCl₂]BF₄] · CH₃CN Niobocenium and tantalocenium compounds of the type (C₅H₅)₂MCl₂]X (X = BF₄, PBh₄, PF₆) were synthesized from the metallocene dichlorides and ferricenium salts, (C₅H₅)₂Fe]X, in methylene dichloride or tetrahydrofuran. With acetonitrile as solvent (C₅H₅)₂MCl₂]X · CH₃CN complexes are formed. Stable methyl compounds of the type (C₅H₅)₂M(CH₃)₂]X were obtained, when (C₅H₅)₂Ta(CH₃)₂ is oxidized by means of ferricenium salts. The new complexes were characterized by elemental analysis, i. r., and ¹H n.m.r. spectra. The structure of (C₅H₅)₂NbCl₂]BF₄] · CH₃CN has been determined by X-ray structure analysis. The compound crystallizes in the orthorhombic space group Cmcm with a = 8.324(12), b = 19.581(13), c = 9,563(8) Å and Z = 4. The coordination geometry of the Nb atom is tetrahedrally.