Michael F. A. Dove

Vanadium(V) oxytrinitrate, VO(NO3)3. A powerful reagent for the nitration of aromatic compounds at room temperature under non-acidic conditions

Vanadium(V) oxytrinitrate is an easy to handle reagent which can be used to nitrate a range of substituted aromatic compounds in dichloromethane at room temperature, leading to >99% yields of nitration products in most cases.

Crystal structures of the difluorophosphate complexes, Co(O2PF2)2·2MeCN and Cu(O2PF2)2

The structures of two new difluorophosphates, Co(O2PF2)2·2MeCN and Cu(O2PF2)2, have been determined from single-crystal X-ray data. The former crystallises in the space group Cmca, Z= 4, with a= 9.227(4), b= 13.871(5), and c= 9.471(4)A, and the structure has been refined to R= 0.046 for 489 observed reflections. The compound is polymeric with bridging difluorophosphate groups, with the cobalt atom in octahedral co-ordination to four oxygen atoms and two nitrogen atoms from the traps oriented acetonitrile molecules. The copper compound belongs to the space group Fddd, Z= 48, with a=10.134(4), b= 24.495(9), and c= 34.058(10)A, and the refinement converged at R= 0.067 for 1 587 observed reflections. It also has a polymeric structure with two independent copper atoms and bridging difluorophosphate groups. Each copper atom has four near oxygen neighbours but distorted-octahedral co-ordination is completed by two longer contacts to oxygen atoms of symmetry-related difluorophosphate groups. This tridentate function for the difluorophosphate group has not previously been observed.

The synthesis, properties and structures of the tetraphenyl-arsonium salts of [V2O3(NO3)2X4]2−, X Cl or NO3

Abstract The complexes [Ph4As]2[V2O3(NO3)6], 1 and [Ph4As]2[V2O3Cl4(NO3)2], 2, crystallise from solution in the reaction of tetraphenylarsonium nitrate with VO(NO3)3 and VOCl3, respectively. The compounds were characterised by their IR and Raman spectra and single crystal X-ray analysis. Compound 1 crystallises in the triclinic space group P 1 , a = 9.580(1), b = 10.782(2), c = 13.631(2) A , Z = 1 and R = 0.059, whilst 2 crystallises in the monoclinic space group P21/c, a = 10.176(1), b = 17.691(2), c = 13.955(2), Z = 2 and R = 0.034. The crystal structures show that the dianions are related, the vanadium atoms in both species possess distorted octahedral symmetry, this being achieved by one terminal and one bridging oxygen atom, one bidentate nitrate group and four other monodentate ligands. An unusual feature of 1 is the presence of both monodentate and bidentate modes of nitrate coordination whilst 2 is the first example of a mixed halonitrato species of vanadium(V) to be isolated.

LABORATORY METHODOLOGIES FOR PROPELLANT CORROSION RESEARCH

Storable liquid propellants are stored for extended periods of time in metal tankage prior to usage in rocket engines. Knowing the chemical interaction of the propellant and the tankage material is essential to evaluating the structural integrity of the tankage hi service and determining if the propellant remains within specifications at the time of use. Some of this information has been obtained through long duration storage studies for periods of over 20 years in some cases. It is desirable to establish valid methods to obtain quantitative data to project long-term corrosion rates in lieu of real-time storage experimentation. Experimental methods and techniques currently used in obtaining such corrosion data and their theoretical basis are described in this article. These include 1) electrochemical: dc polarization and ac impedance measurements; 2) weight loss; and 3) surface analytical: x-ray photoelectron spectroscopy, auger electron spectroscopy, and optical microscopy. This article presents a description of the fundamental methods used by two research organizations and a comparison of these methods and equipment. These techniques are valid for evaluation of corrosion rates on various fuel and oxidizer propellants. The results of specific research with nitric acid based oxidizers with various aluminum alloys are presented in a companion article.

Multinuclear n.m.r. spectroscopy of [NEt4][SbXnF6 –n], X Br or Cl, and [NEt4][AsClnF6 –n] in solution in MeCN

The anions in the title, n 1–6, have been conclusively characterised in solution by 19F, 75As, and 121Sb n.m.r. spectroscopy and, for n 1–5, shown to be stable with respect to fluorine redistribution reactions.

Chemistry in fuming nitric acids—I. NMR spectroscopic study of PF5, HPO2F2 and P4O10 in the solvent system 44 wt.% N2O4 in 100% HNO3

Abstract 31 P and 19 F NMR spectroscopy has been used to elucidate the nature of the interaction of PF 5 , HPO 2 F 2 and P 4 O 10 with the solvent system 44 wt.% N 2 O 4 in 100% HNO 3 (“High Density Acid”, HDA). PF 5 generates the species PF 6 − , HPO 2 F 2 and HF (with some H 2 PO 3 F present as a minor product). HPO 2 F 2 gives rise to H 2 PO 3 F and HF (with smaller amounts of PF 6 also present). The 31 P NMR spectrum of P 4 O 10 in HDA exhibits four resonances assigned to P(OH) 4 + , H 4 P 2 O 7 , (HPO 3 ) 4 and a mixture of cyclic and branched phosphoric acids, respectively.

Trifluoroacetate as a bridging ligand for antimony(V): crystal and molecular structures of µ-fluro-µ-trifluoroacetato-bis[tetrafluoroantimony(V)](1) and of µ-oxo-di-µ-trifluoroacetato-bis[trifluoroantimony(V)](2)

Crystals of title compound (1), Sb2(O2CCF3)F9, are monoclinic. Space group P21/c with a= 9.386(6), b= 15.119(8), c= 16.250(7)A, β= 110.52(11)°, and Z= 8. The asymmetric unit contains two equivalent but crystallographically independent binuclear complexes in which the Sb atoms are bridged by a F atom (Fb) and by a trifluoroacetato-group. The distorted octahedral co-ordination at each Sb centre is completed by four terminal F atoms (Ft). The mean bond distances are : Sb–Fb 2.025(21), Sb–O 2.026(23), and Sb–Ft 1.836(24)A. The heavy atoms have been located directly and full-matrix least-squares refinement with anisotropic thermal parameters for the Sb atoms has given R= 0.090 with 1 791 independent observed reflections. Title compound (2), Sb2O(O2CCF3)2F6, crystallizes in the monoclinic space group Cc with a= 12.322(6), b= 13.867(8), c= 9.443(5)A, β= 122.75(5)°, and Z= 4. The two Sb atoms are bridged by an oxygen atom (Ob) and by two trifluoroacetato-groups with the octahedral co-ordination at Sb completed by terminal fluorines (Ft). The binuclear complex has approximate C2v symmetry and exhibits the following mean bond distances: Sb–Ob 1.893(21), Sb–O 2.064(16), and Sb–Ft 1.840(17)A. The analysis is based on 1 760 independent observed reflections and refined by weighted full-matrix least-squares analysis to R= 0.043.

Preparation and X-ray crystal structure of Sn3F8

The oxidation of SnF2 in HF with O2, F2, or SO2 yields insoluble Sn3F8; the crystal structure of this new compound shows trans-fluorine-bridged SnIVF6 units linked to polymeric SnIIF chains.

Aluminum alloy compatibility with gelled inhibited red fuming nitric acid

Michael F. A. Dove* University of Nottingham, Nottingham NG7 2RD, England, United Kingdom Norman Logant University of Alabama in Huntsville, Huntsville, Alabama 35899 Jeremy P. Maugert University of Nottingham, Nottingham NG7 2RD, England, United Kingdom Barry D. Allan§ Redstone Arsenal, Huntsville, Alabama 35898 and Ramona E. ArndtH and Clark W. Hawk** University of Alabama in Huntsville, Huntsville, Alabama 35899

The reaction of ionic nitrites with liquid dinitrogen tetraoxide

Abstract The reaction of nitrites of Na + , Bu 4 n N + and Ni 2+ with liquid dinitrogen tetraoxide and the factors affecting the rate and extent of the reaction have been studied. Oxidation occurs to the corresponding nitrate in a manner consistent only with the heterolytic dissociation of N 2 O 4 into NO + and NO 3 − . The synthesis of anhydrous Ni(NO 2 ) 2 is described in detail.