摘要:

A pair of laminar, premixed, CH4–O2flames above 2000 K at atmospheric pressure, one fuel-rich (FR) and the other fuel-lean (FL), were doped with ~10−6 mol fraction of the second-row transition metals Y, Zr, Nb, and Mo. Since these hydrocarbon flames contain natural ionization, metallic ions were produced in the flames by the chemical ionization (CI) of metallic neutral species, primarily by H3O+and OH−as CI sources. Both positive and negative ions of the metals were observed as profiles of ion concentration versus distance along the flame axis by sampling the flames through a nozzle into a mass spectrometer. For yttrium, the observed ions include the YO+•nH2O (n = 0–3) series, and Y(OH)4−. With zirconium, they include the ZrO(OH)+•nH2O (n = 0–2) series, and ZrO(OH)3−. Those observed with niobium were the cations Nb(OH)3+and Nb(OH)4+, and the single anion NbO2(OH)2−. For molybdenum, they include the cations MoO(OH)2+and MoO(OH)3+, and the anions MoO3−and MoO3(OH)−. Not every ion was observed in each flame; the FL flame tended to favour the ions in higher oxidation states. Also, flame ions in higher oxidation states were emphasized for these second-row transition metals compared with their first-row counterparts. Some ions written as members of hydrate series may have structures different from those of simple hydrates; e.g., YO+•H2O = Y(OH)2+and ZrO(OH)+•H2O = Zr(OH)3+, etc. The ion chemistry for the production of these ions by CI in flames is discussed in detail.Keywords: transition metals, ions, flame, gas phase, negative ions.

ISSN:0008-4042    

DOI:10.1139/v95-280

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The rhenium(V) and technetium(V) complexes: [ReO(apa)], [{ReO(epa)}2O], and [TcOCl(epa)] have been prepared from a potentially pentadentate N3O2ligand,N,N′-3-azapentane-1,5-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione) (H3apa), or a potentially tetradentate N2O2ligand,N,N′-ethylene-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione) (H2epa). The N2O2complexes were synthesized in low yields. There was also evidence indicating that H2ppa,N,N′-propylene-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione), hydrolyzed in the course of coordination, forms a rhenium complex of the bidentate monoprotic (O,O) dehydroacetate (dha−), [Re(dha)Cl2(OPPh3)(PPh3)]•EtOH. The structure of this complex was determined by X-ray crystallography. Crystals of [Re(dha)Cl2(OPPh3)(PPh3)] EtOH (C44H37Cl2O5P2Re•C2H6O) are monoclinic,a = 11.064(2),b = 24.167(2),c = 16.6687(8) Å, β = 98.779(7)°,Z = 4, space groupP21/c. The structure was solved by the Patterson method and refined by full-matrix least-squares procedures toR = 0.030 andRw = 0.025 for 6942 reflections withI ≥ 3σ(F2).Keywords: dehydroacetic acetate based Schiff base ligands, rhenium, technetium, N3O2Schiff base, N2O2Schiff base, oxygen transfer.

ISSN:0008-4042    

DOI:10.1139/v95-281

出版商:NRC Research Press    

年代:1995

数据来源: NRC