Synthesen und Strukturen neuer Komplexes des 2,2′‐Bipyridins mit Niob, Molybdän, Wolfram und Rhenium in hohen Oxidationsstufen

Syntheses and Structures of New 2,2′‐Bipyridine Complexes of Niobium, Molybdenum, Tungsten, and Rhenium in High Oxidation States Exchange of oxo for chlorine ligands by means of hexamethyl‐disiloxane provides an easy and effective synthesis of the oxo halides (bipy)M^VOCl₃ (bipy = 2,2′‐bipyridine, C₁₀H₈N₂; M = Nb, 1c; Re, 2c; W, 3c) and (bipy)M^VIO₂Cl₂ (N = Mo, 6a;W, 6b). Starting from ReCl₅ the structurally (X‐ray) characterized byproduct (bipy)Re^IVCl₄ (2b) is also formed. Dirhenium heptaoxide (7) is converted into the complex (bipy)Re^VIIO₃Cl (8) upon treatment with chlorotrimethylsilane in the presence of 2,2′‐bipyridine, thus being now easily available a key compound in rhenium chemistry. The new imido complexes of composition (bipy)MoVI(NR)₂Cl₂ [R = C(H₃)₃, 9a; C₆H₅, 9b] are accessible from 6a and the corresponding silylated amines. The rhenium and tungsten complexes 2b and 6b, resp., exhibit octahedral structures in the crystal, with that of 6b being distorted as a result of different ligands and intermolecular contacts.