Diazenido-complexes of molybdenum and tungsten

The diazenido-complexes [MX(N2H)(dppe)2](M = Mo or W: X = F, Cl, or Br; dppe = Ph2PCH2CH2PPh2) have been prepared by treatment of the corresponding diarene, [MX2(NH:NH)(dppe)2], or hydrazido(2–), [MF(N-NH2)(dppe)2][BF4], complexes with triethylamine or aqueous potassium carbonate. With 1 mol of anhydrous acid they regenerate the parent diazeneor hydrazido(2–) complexes. The complex [WBr(N2H)(dppe)2] reacts with organic bromides to give the known complexes [WBr2(N2HR)(dppe)2](R = Me or MeCO). The N2H ligand is not displaced by trialkylphosphines but nitrogen mono-oxide displaces it quantitatively to give the nitrosyl complexes [MX(NO)(dppe)2]. Spectroscopic data for these complexes and their 15N and 2H derivatives are described.