μ-Nitridokomplexe von Molybdän(IV) und Wolfram(V): Mo2NBr5 und W2NBr7

μ-Nitrido Complexes of Molybdenum(IV) and Tungsten(V): Mo₂NBr₅ and W₂NBr₇ Mo₂NBr₅ was prepared by the reaction of molybdenum tetrabromide with the bromide of Million's base, Hg₂N]Br, in boiling CH₂Br₂. It forms a brown, moisture sensitive, paramagnetic crystal powder (μ_eff = 1.12 B.M.). In an analogous manner W₂NBr₇ was synthesized from tungsten pentabromide; it is a black, moisture sensitive, paramagnetic crystal powder (μ_eff = 0.77 B.M.). Neither Mo₂NBr₅ nor W₂NBr₇ can be converted to anionic complexes by addition of PPh₄Br. Nevertheless, the ion W₂NBr₈] ? could be obtained as PPh₄ ⊕ salt by the reaction of PPh₄W₂NCl₁₀] with excess trimethylbromosilane. PPh₄W₂NBr₈] reacts with PPh₄Br yielding PPh₄WNBr₄] and (PPh₄)₂W₂Br₁₀]. A new method of synthesis for WNBr₃ was found in the reaction of WBr₆ with Hg₂N]Br in dibromomethane at 80°C. The i.r. spectra are reported.