Richard J. Hobson

Reactions of metal dialkyl dithiophosphates part IV. The crystal structure of [Ag{S2P(OEt)2}2]22− a silver anion containing monodentate and tridentate dialkyl dithiophosphate groups

Abstract The reaction between Ag{(S2P(OEt)2} and [Me4N] [S2P(OEt)2] yields [Me4N] [Ag{S2P(OEt)2}2] (1), crystals of which are monoclinic, space group P21/c, with a = 12.966(11), b = 16.159(14), c = 12.898(15) A, β = 106.0(1)°, Z = 2; 2545 significant reflections were measured on a diffractometer and the structure was refined to R = 0.068 (Rw = 0.088). 1 contains the centrosymmetric species [Ag{S2P(OEt)2}2]22− in which two dialkyldithiophosphate ligands bridge the two metal centres while the other two dialkyldithiophosphate residues are monodenrate. The two sulphur atoms of the bridging dialkyldithiophosphate ligands bond very differently; thus while S(1) bridges two silver atoms [2.679(3) and 2.868(3) A], S(2) is only bonded to one metal atom [2.728(3) A]. Thus the ligands in the ring act simultaneously as bridging and chelating ligands. The four coordinate geometry around the metal is completed by S(3) [AgS(3) 2.517(3) A] which is from the monodentate ligand.

Sol–gel-derived vanadium and titanium oxides as cathode materials in high-temperature lithium polymer-electrolyte cells

Binary and ternary vanadium- and titanium-containing xerogels have been prepared by hydrolysis of the metal isopropoxides and subsequent condensation. Powder X-ray diffraction (XRD) has been used to show that pure gel-derived titanium(IV) oxide possesses a struture resembling poorly crystalline anatase, whereas for all the vanadium-containing materials prepared in isopropyl alcohol solution the data are consistent with some two-dimensional (2D) order and a similar short-range arrangement of VO5 moieties to that in crystalline V2O5. In contrast, the vanadium oxide xerogel obtained from an aqueous milieu shows evidence only of one-dimensional order, interlayer distance 14.2 A. Thermal analysis and XRD have been used to show that all the vanadium-containing gels lose water in three stages and that no structural change occurs until the third stage of water loss, which occurs simultaneously with crystallisation.The oxides have been employed as the active component of the cathode in lithium polymer-electrolyte cells operating at 120°C and their cycling performance has been investigated. The binary oxides showed no improvement in performance over similar crystalline materials whereas the ternary materials, whether chemical or physical mixtures, showed good reversibility and gave observed energy densities which compared favourably with that of V6O13 in a similar cell. This improvement in performance has been attributed to the preferential reduction of the TiIV over VIV near the low-voltage limit which prevents a reorganisation of the microstructure of the material.

Preparation, crystal and molecular structure of trichlorosulphido(triphenylphosphine sulphide)niobium(V)

Abstract The reaction between NbSCl3 and triphenylphosphine sulphide leads to the formation of the 1:1 adduct, crystals which are triclinic, space group P 1 , with a = 12.524(5), b = 10.193(4), c = 17.823(6) A, α = 103.80(3), β = 102.60(4), γ = 72.02(4)°, Z = 4. The structure was solved by Patterson and Fourier methods using diffractometer data and refined to R 0.058 for 2880 significant reflections. The unit cell contains two five-coordinate monomers and one centrosymmetric six co-ordinate dimer, the coexistence of which is a most unusual feature in the solid state. The niobium atom is displaced from the plane formed by the three chlorine atoms and the ligand sulphur atom towards the sulphido sulphur atom [0.553(2) A, monomer, 0.397(2) A, dimer]. This displacement is larger than any yet found in adducts of NbOCl3.

Synthesis, single-crystal structure and magnetic properties of orthorhombic CuNb2O6

The conditions necessary for the synthesis of the two reported polymorphs of CuNb2O6 from the binary oxides have been investigated. The black, orthorhombic phase has been prepared in a pure crystalline form and its single-crystal structure determined. It is isomorphous with the MIINb2O6 columbite system (orthorhombic, a= 14.019(11)A, b= 5.623(7)A, c= 5.107(7)A, space group Pbcn) but the CuO6 octahedra display a large tetragonal distortion [Cu–O, 1.976(6)× 2, 1.973(6)× 2, and 2.383(6)× 2 A]. Above 225 K the compound is magnetically dilute and obeys the Curie law (µeff= 1.91µB), whereas Curie–Weiss behaviour was observed between 225 and 50 K (θ=–30 K) with a maximum susceptibility at 20 K. The magnetic data have been analysed in terms of a onedimensional antiferromagnetic chain model.The yellowish-green, monoclinic phase is more difficult to prepare in a pure form than the black, orthorhombic phase. Some provisional details for its preparation are reported.

Synthesis, structure and magnetic properties of monoclinic CuNb2O6 and the electronic spectra of both polymorphs of CuNb2O6

The conditions necessary for the synthesis of the monoclinic polymorph of CuNb2O6 from the binary oxides are reported. The yellow–green monoclinic phase has been prepared in a pure microcrystalline form and its structure determined by means of a Rietveld profile-refinement of powder X-ray data. The structure is a monoclinic distortion of the MIINb2O6 columbite type [a= 4.9991(1)A, b= 14.1566(4)A, c= 5.7540(1)A, β= 91.718(1)°, space group P21/c] with a small tetragonal distortion of the CuO6 octahedra [Cu—O, 2.038(16), 2.079(19), 1.968(16), 2.016(16), 2.150(20) and 2.168(18)A]. Above 90 K the compound is magnetically dilute and obeys the Curie law (µeff= 1.96 µB). Below 90 K there is a fairly abrupt departure from simple Curie law behaviour and a Neel point occurs at 25 K. The magnetic data have been analysed in terms of a dimeric model. The electronic spectrum of the black orthorhombic form of CuNb2O6 is consistent with a band structure whereas that of the yellow–green monoclinic form is characteristic of isolated copper(II) ions. The results of the study suggest a likely explanation for the variability in colour of the CuNb2O6 polymorphs.

Preparation, properties, and crystal and molecular structures of the cyanomethane adducts of niobium(IV) chloride and di-µ-sulphido-bis[dichloroniobium(IV)]

The cyanomethane adduct of NbCl4 analyses for NbCl4·3CH3CN (1). A crystal-structure determination of this species shows that it contains cis octahedral [NbCl4(NCMe)2] and a solvent CH3CN molecule. The unique bond lengths are Nb–N 2.220(13)A and Nb–Cl 2.328(2), 2.343(6), and 2.349(4)A. The crystals of (1) are orthorhombic with unit-cell dimensions a= 10.437(11), b= 13.883(12), c= 9.828(9)A, Z= 4, and space group Pnma. A total of 729 reflections above background have been collected on a diffractometer and refined to R 0.051.When the cyanomethane adducts of NbX4(X = Cl or Br) are treated with Sb2S3 in cyanomethane, adducts of NbX2S (X = Cl or Br) are formed. The products contain [{NbX2S(NCMe)2}2] in which there is a [graphic omitted] ring. The crystal structures of two compounds, (2) and (3), containing the [{NbCl2S(NCMe)2}2] dimeric unit have been determined. In (2) there are two molecules of occluded CH3CN for each dimer while (3) has one. Both (2) and (3) are triclinic with space group P, with (2) having a= 9.031 (7), b= 9.367(6), c= 8.360(8)A, α= 108.72(9), β= 94.93(7), γ= 105.70(8)°, Z= 1 and (3) having a= 14.965(18), b= 8.838(17), c= 9.543(23)A, α= 112.42(18), β= 84.39(28), γ= 103.65(21)°, Z= 2. For (2), 1 434, and for (3), 1 530, independent reflections above background have been collected on a diffractometer and refined to R 0.056 and 0.050 respectively.The dimer configurations in (2) and (3) are identical. The niobium atoms are in a pseudo-octahedral environment consisting of two cis sulphur [Nb–S 2.338(8)–2.349(7)A], two trans chlorine [Nb–Cl 2.383(6)–2.403(5)A], and two cis nitrogen atoms [Nb–N 2.286(26)–2.334(22)A]. In addition, in each dimer there is a Nb–Nb single bond [2.862(2)–2.872(3)A].

Reactions of [Zn{S2P(OR)2}2] with nitrogen bases and the single-crystal X-ray structures of [Zn{S2P(OPri)2}2]·H2NCH2CH2NH2 and [Zn{S2P(OPri)2}2]·NC5H5

The adducts [Zn{S2P(OR)2}2]·L [L = H2NCH2CH2NH2(en), MeHNCH2CH2NHMe (dmen), Me2NCH2CH2NMe2(tmen), 2,2′-bipyridyl,1,10-phenanthroline,2,9-dimethyl-1,10-phenanthroline, or pyridine; R = Et or Pri] and the ionic compounds [Zn(en)3][S2P(OR)2]2 and [Zn(dmen)][S2P(OR)2]2 have been isolated by treating [Zn{S2P(OR)2}2] with L in the appropriate stoicheiometry. The crystal structures of [Zn{S2P(OPri)2}2]·en (1) and [Zn{S2P(OPri)2}2]·py (2) have been determined: (1), monoclinic, space group P21/c, with a= 13.402(8), b= 16.470(9), c= 12.294(7)A, β= 99.0(1)°, and Z= 4; (2), monoclinic, space group P21/n with a= 21.28(1), b= 8.35(1), c= 16.27(1)A, β= 99.5(1)°, and Z= 4. Diffractometer data were collected for both crystals [of which 1 340 (1) and 1 940 (2) were above background] and both structures were refined to R 0.073. In (1) the zinc atom is four-co-ordinate forming two Zn–N bonds [2.077(13) and 1.922(16)A] to the bidentate ethylenediamine molecule and two Zn–S bonds [2.292(5) and 2.331(5)A] to the monodentate dithiophosphate ligands. In (2) the zinc atom is five-co-ordinate being bonded to pyridine [Zn–N 2.015(12)A], and to two bidentate dithiophosphate ligands. One ligand is bonded to the metal more symmetrically [Zn–S 2.502(4) and 2.358(4)A] than the other [Zn–S 2.269(4) and 3.032(4)A]. The 31P n.m.r. spectra of a number of these compounds have been examined. A correlation between the positions of the resonances and the mode of bonding of the [S2P(OR)2]– groups to the metal has been established.

Gas-phase electron diffraction study of the molecular structure of tetrachloro-oxo-rhenium(VI), ReOCl4

Abstract The molecular structure of ReOCl4 has been studied by gas-phase electron diffraction at an average nozzle temperature of 70°C. The experimental data were fitted to a square-pyramidal model of C4v symmetry in which the rhenium atom is above the plane of the four chlorine atoms. The bond distance are re(ReO) = 1.663(9) A, ra(ReCl) = 2.270(5) A, and ∠cOReCl = 105.5(15)°. The estimated uncertaintie; are 2σ including estimates of correlation in the experimental data and uncertainties in the electron wavelength.

Crystal and molecular structure of [{Ag[S2P(OEt)2]·PPh3}2]

The reaction of [Ag{S2P(OEt)2}] with triphenylphosphine yields [{Ag[S2P(OEt)2·PPh3}2](1). The crystal structure of compound (1) has been determined. The crystals are monoclinic, space group P21/c, a= 14.965(13), b= 9.753(8), c= 18.438(12)A, β= 119.0(1)°, and Z= 2. 2 401 Independent reflections above background were measured on a diffractometer and the structure was refined to R= 0.056. The structure contains the centrosymmetric species [{Ag[S2P(OEt)2]·PPh3}2], in which the two dithiophosphate ligands bridge the two metal centres in a unique fashion. The bonding mode of the two sulphur atoms of the dithiophosphate ligand is very different; while S(1) bridges two silver atoms [2.502(2) and 2.821(2)A], S(2) is only bonded to one [2.810(2)A]. The silver atoms are also bonded to triphenylphosphine [Ag–P 2.404(2)A] to complete a distorted four-co-ordinate geometry.

Dimeric tungsten(V) compounds containing [(S)W(µ-S)2W(S)]2+. Syntheses and structures of di-µ-sulphido-bis[(diethyl dithiophosphato-SS′)sulphido-tungsten(V)] and di-µ-sulphido-bis[(N,N-diethyldithiocarbamato-SS′)-sulphidotungsten(V)]

The compound [W2S4{S2P(OEt)2}2] has been isolated by two alternative routes: (a) treatment of [WS4]2– with HS2P(OEt)2 and (b) reaction of WS2Cl2 with [NH4][S2P(OEt)2]. The oxidation product of both reactions is [(EtO)2P(S)S–]2. The two routes led to two different crystal forms, (1a) and (1 b), of the product [W2S4{S2P(OEt)2}2]. Treating [W2S4{S2P(OEt)2}2], either form, with Na(S2CNEt2) gave [W2S4(S2CNEt2)2](2). The crystal structures of (1a), (1b), and (2) have been determined. (1a) is monoclinic, space group P21/n, with a= 18.230(11), b= 12.905(11), c= 10.153(12)A, β= 90.5(1)° and Z= 4; (1b) is monoclinic, space group P21/a, with a= 13.844(12), b= 10.280(9), c= 17.907(13)A, β= 113.2(1)°, and Z= 4; (2) is orthorhombic, space group P212121, with a= 13.80(1), b= 10.49(1), c= 14.59(1)A, and Z= 4. Diffractometer data were collected for all three compounds [independent reflections above background, 5 787 (1a), 3 658 (1b), and 2 134 (2)], the structures determined by the heavy-atom method and refined to give R= 0.061, 0.084, and 0.066 for (1a), (1b), and (2) respectively. All three compounds contain the syn form of [(S)W(µ-S)2W(S)]2+{bond length ranges 2.054(12)–2.116(5)[W–S(terminal)], 2.279(8)–2.325(9)[W–S(bridging)], and 2.795(2)–2.819(1)A(W–W)}. In addition to the bonds in the [W2S4]2+ moiety, each tungsten atom is co-ordinated to a bidentate ligand with W–S bond lengths in the range 2.429(9)–2.498(6)A. Apart from the W–W bond each metal atom is five-co-ordinate and has a distorted square-pyramidal structure.