Diazene-N-(di-imide) and hydrazido-(2–)N-(aminoimido) complexes: the addition of acids to dinitrogen complexes

TLDR: In this article, the protonation and reduction of dinitrogen in a mononuclear complex are described, and the structural implications of the i.m.n.r., 1H and 31P n.r.

Abstract: The protonation and reduction of dinitrogen in a mononuclear complex are described. The diazene compounds [MX2(N2H2)(dpe)2](I; M = W, X = Cl or Br; M = MO, X = Br; dpe = Ph2PCH2CH2PPh2), and hydrazido (2–)N complex salts, [Mo(N2H2)(depe)2]X (X = Cl or Br; depe = Et2PCH2CH2PEt2) and trans-[WCl(N2H2)(PMe2Ph)4]Cl were prepared by the reaction of trans-[M(N2)2(diphos)2](M = MO or W; diphos = dpe or depe) or cis-[W(N2)2(PMe2Ph)4] with an excess of the appropriate hydrogen halide. Compounds (I) contain labile halogen and are converted into the hydrazido-(2–)N complex salts [MX(N2H2)(dpe)2]Y (Y = BPh4, ClO4, or PF6, M = W; Y = BF4, M = MO) by treatment with NaBPh4, LiClO4, NaPF6, or [NEt4]BF4 as appropriate. The structural implications of the i.r., 1H and 31P n.m.r. spectroscopic properties of the N2H2 compounds and of their 15N analogues are discussed.With only 2 mol equiv. of HCl, trans-[W(N2)2(dpe)2] gives the hydride [WH(N2)2(dpe)2]HCl2 and trans-[Mo(N2)2(dpe)2] gives the dihydride [MoH2Cl2(dpe)2]. [WH(N2)2(dpe)2]HCl2 is converted into [WH2Cl2(dpe)2] in refluxing methanol and [WCl2(N2H2)(dpe)2] gives [WCl2{N2H(COCH3)}(dpe)2] with acetyl chloride or acetic anhydride.This work provides the first chemical evidence that dinitrogen is as likely to be reduced at a mono- as at a bi-metal site in nitrogenase.