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[Mo3S7(dtc)3]dtc (dtc = S2CNEt2) reacts with one or more equivalents of TCNQ (7,7,8,8-tetracyanoquinodimethane) in CH3CN to form radical-anion salts [Mo3S7(dtc)3]2(TCNQ)2 (1) and [Mo3S7(dtc)3](TCNQ)2 (2), respectively. By an analogous method from [Mo3Se7(dtc)3]dtc the seleno complex [Mo3Se7(dtc)3](TCNQ)2 (3) was obtained. The structure of 1 was established by X-ray structural analysis. The crystals are orthorhombic, space group Pbca, a=24.388(4), b=14.043(2), c=25.224(6) A. The structure has been solved to RF 0.049. The geometry of the [Mo3S7(dtc)3]+ cation is normal; the most interesting feature of the structure is the presence of rather short contacts between N atoms of TCNQ and S atoms of S2 ligands of the cation (the S…N distances are 2.91-2.95 A). The TCNQ anions form centrosymmetrical dimers (the separation between the corresponding planes is 3.16 A), so the formula of I can be written as [MO3S7(dtc)3]2(TCNQ)2.

Chromium hexacarbonyl reacts with (Et2NCS2)2Y (Y  Se, Te) in the presence of Me3NO·2H2O to form Cr(S2CNEt2)3. Tungsten hexacarbonyl, under the same conditions, gives rise to WSe2(S2CNEt2)3·0.5H2O (1) and [W(S2CNEt2)4]2W6O19 (2). The structures of 1 and 2 were established by X-ray structural analysis. The tungsten in complex 1 has a distorted dodecahedron coordination. The structure of 2 is ionic, and contains the well known W6O192− anion and the W(S2CNEt2)4+ cation containing dodecahedral tungsten.

New methods for the synthesis of triangular M3Se74+ and M3Se44+ complexes soluble in organic solvents have been developed which proceed from polymeric M3Se7X4 (M = Mo, W; X = Cl, Br). Heating of Mo3Se7Cl4in a PPh4Cl melt has produced the (PPh4)2Mo3Se7Cl6 salt. Selenobromide complexes of molybdenum and tungsten are less stable and have been converted to M3Se7(dtc)4 complexes by reacting them with NaS2NCEt2·3H2O (Nadtc·3H2O) in CH3CN. The structure of M3Se7(dtc)4 (M = Mo, W) has been determined by X-ray structural analysis: a = 16.728(5), b=18.604(7), c=13.324(3) A, β=99.12(3)°, Z=4, P21/c, RF=0.1344 for W3Se7(dtc)4; a=16.652(5), b=18.614(8), c=13.337(3) A, β=99.11(2)°, Z=4, P21/c, RF=0.0628 for Mo3Se7(dtc)4. Heating of M3Se7X4 in a melt of 1,10- phenanthroline (phen) produces salts containing M3Se7(phen)34+ with different anions (Cl−, Br−, ZnCl42−, ZnBr42−). The action of phosphines on M3Se74+ complexes gave M3Se74+ complexes Mo3Se4(dtc)4(PPh3) and Mo3Se4(dppe)3Cl4 (dppe is Ph2PCH2CH2PPh2).

Alkylammonium salts, W 2 34 S 4 X 4 2− (X = Cl, Br), M 2 34 S 4 Br 8 2− (M = Mo, W) and Mo 2 34 S 6 O 2 2− , have been obtained from 34 S 8 . IR and Raman spectra of these compounds have been studied and the normal vibrations calculated. A number of vibrations involving sulphur atoms [for example v (MS), v (SS)] are characteristic, which allows vibrational spectroscopy to be used to study the changes occurring in the metal-sulphur containing fragments. The interaction of W 2 (μ 2 -S)(μ 2 -S 2 )Br 8 2− with 34 S 8 was shown to produce W 2 (μ 2 -S 2 ) 2 Br 8 2− . The reaction of Mo 2 (μ 2 - 34 S 2 ) 2 Cl 4 C 4/2 with S x 2− results in the replacement of 34 S by 32 S to produce the Mo 2 (μ 2 -S 2 ) 2 (S 2 ) 4 2− complex.

The Mo3S7X62− salts (X=Cl, Br, NCS) interact with KSeCN at room temperature in CH3CN to form KSCN and Mo3S4Se3(NCS)62−. The stereochemistry of this reaction has been studied and it was shown that substitution only occurs at the equatorial sulfur atoms of the μ2-S2 ligand. By treating (Et4N)2Mo3S4Se3(NCS)6 with conc. HCl (Et4N)2Mo3S4Se3Cl6 was prepared from which (PPN)2Mo3S4Se3Cl6 (IIIb) was obtained by the exchange of the cation. The structure of the latter was established by X- ray structural analysis. The crystals of lIIb are triclinic, space group P1, a = 13.650 (2), b = 18.159(3), c = 19.009(3) A; α = 99.48(1), β = 109.23(1), γ = 109.32(1)° Z = 2. With a total number of independent reflections of 7937, the structure has been solved to R = 0.054 (Rw = 0.077). The selenium atoms lie essentially in the plane of the isosceles Mo3 triangle. The SSe distances are 2.156(5)–2.166(3) A; MoMo distances are 2.765(2)–2.787(2) A. The equatorial sulfur of the μ2-S2 group was found to undergo isotopic exchange with the thiocyanate sulfur. The interaction of (Et4N)2Mo334S7Cl6 with KSCN afforded, according to the vibrational spectroscopy data, (Et4N)2Mo3(μ3-34S)(μ2-32S34S)3(NCS)6.

The results of studies of halogen-containing yttrium-barium cuprates are reviewed. Different methods for the synthesis of YBa 2 Cu 3 O 7− x Hal y phases are discussed and the structural features and physical properties of the phases are analysed. Attention is given mainly to the low-temperature methods which allow preparation of single-phase samples. Mechanisms of halogen insertion into the YBa 2 Cu 3 O 7− x lattice are discussed, as well as the role of different structural fragments in the high-temperature superconductivity phenomenon.

The interaction of solid W3S7Br4 or W3Se7Br4 with Et4NBr under vibrational mill conditions followed by extraction with acetonitrile resulted in the isolation of (Et4N)2W3S7Br6 (1) and (Et4N)2W3Se7Br6 (2) salts. Treatment of the product of the analogous reaction of Mo3Se7Br4 and Et4NBr with sodium diethyldithiocarbamate (Nadtc) resulted in [Mo3Se7(dtc)3]dtc (4). The M3Y74+ (Y = S, Se) cluster fragments are retained in all of these reactions. By dissolving 1 in conc. hydrochloric acid and adding PPNCl, the (PPN)2W3S7Cl6 salt (5) was obtained, for which an X-ray study has been performed. Selected distances for the cluster anion W3(μ3-S)(μ2-S2)3Cl62− are 2.7270(7)-2.7445(6) A for WW, 2.360(3)-2.361(3) A for W—(μ3,-S), 2.032(4)–2.052(4) A for SS, 2.429(3)- 2.459(2) and 2.493(4)–2.519(3) A for WCl (for cis and trans positions with respect to μ3-S, respectively). Rather short distances (3.17–3.21 A) between the chlorine atoms and sulphur atoms of the μ2-S2 ligands of the adjacent anions were noted. The interaction of 2 with 1,2-bisdiphenylphosphine ethane (dppe) is accompanied by elimination of selenium to produce W3Se4Br3(dppe)3]Br (6).

Methods for the synthesis of triangular thiohalogenide complexes of tungsten W3S7X4 (XCl, Br) proceeding from metallic tungsten or WS3 have been developed. Ways have been found for converting these polymeric complexes to triangular W3S7X62− complexes which preserve the architecture of the W3(μ3-S)(μ2-S2)34+ cluster fragment. Heating W3S7X4 in a PPh4X melt or in concentrated acids HX in the presence of Et4NX afforded PPh4+ and Et4N+ salts of W3S7X62− (XCl, Br). The structure of (Ph4P)2W3S7Br6 (III) was established by X-ray diffraction analysis. The crystals of III are orthorhombic, a=18.082(2), b=25.834(3), c=27.370(2) A, Z=8, Pbca, R (Rw)=0.049 (0.055). The Et4N+ salt of W334S7Br62− has been obtained and a calculation of the normal vibrations has been performed for W3S7Br62−. Interaction of W3S7Br4, with a KNCS melt or an aqueous solution of (NH4)2Sx involves transformation of the cluster fragment W3S74+ to a W3S44+ fragment to produce W3S4(NCS)95− and W3S4(S4)3(NH3)32− complexes. The structure of (NH4)(H)(H2O)3W3S16(NH3)3 (VI) was established by X-ray diffraction analysis. The crystals of VI are trigonal, a=12.508(1), c=10.112(1) A, Z=2, P31c, R (Rw)=0.029 (0.033).

The thiohalide complex of tungsten (Et4N)2W2S4Br4 interacts with PPh3 to produce the W2S4Br2(PPh3)2·C6H6 complex (I). The crystals of I are triclinic, space group P 1 (a = 10.573(2), b = 14.054(3), c = 16.751(4) A, α = 111.10(2), β = 90.24(1), γ = 110.01(1)°, Z = 2). A total of 1623 independent observed reflections have been obtained on an automated diffractometer and the structure was refined to R = 0.0734. Complex I has a syn-[(S)W(μ2S)2W(S)]2+ fragment. The bromine atoms are in a trans position. The WW distance is 2.813(3) A and the WSt distance is 2.10(1) and 2.115(9) A.

The triangular (NH4)2Mo3S13·2H2O complex interacts with Cl2 and Br2 in CH3CN and with concentrated hydrohalogen acids HX (X = Cl, Br and I) retaining its Mo3(μ3-S)(μ-S2)34+ cluster fragment to produce the Mo3(μ3-S)(μ2-S2)3X62− complexes in high yields. IR and Raman spectra of the Mo3S7X62− complexes have been studied. Salts of Mo3S7X62− (X = Cl, Br) containing 92Mo, 100Mo and 34S isotopes and compounds with μ2-(32S-34S) ligands have been also synthesized. For Mo3S7Cl62−, an analysis of the normal vibrations has been performed. The Mo3S7X62− complexes (X = Cl, Br) interact with phosphines (PPh3 and dppe). The reactions proceed with elimination of the μ2-S2 sulfurs to form sulfides of the phosphines and the phosphine complexes Mo3S4X4·3PPh3 and Mo3S4X4·3dppe containing a Mo3S44+ cluster fragment. It has been shown, for the reaction of Mo3(μ3-34S)(μ2-32Se-34Sa)3Cl62− with PPh3, that it is the equatorial μ2-S2 sulfurs that are predominantly eliminated.

The triangular anionic thio-complex [Mo3S13]2− has been obtained by the reaction of the triangular molybdenum thiobromide Mo3S7Br4 with an aqueous solution of Sx2−. Starting from compounds containing 92Mo, 100Mo and 34S isotopes, the following thio-complexes have been obtained: [92Mo3S13]2−, [100Mo3S13]2−, [Mo334S13]2-, [Mo3(μ3-S)(μ2-S34S)3(34S2)3]2− and [Mo3(μ3-34S)(μ2-34SS)3(S2)3]2−. Along with the nucleophilic substitution of the Br ligands by the terminal S2 ligands, elimination—addition of sulphur in μ2-S2 ligands also takes place. This allows preparation of thio-complexes containing μ2-34S32S ligands. IR and Raman spectra of the thio-complexes have been studied, normal vibrations have been calculated and the bond force constants determined.

In this paper, the authors present the results of magnetic, resistive and gamma-resonance studies on polycrystalline samples of a rhombic and tetragonal modification of the YBa/sub 2/ (Cu/sub 1-x/Fe/sub x/)/sub 3/O/sub 7-/delta// compound and on samples containing both phases. By varying the synthesis and thermal treatment conditions it was possible to prepare samples with different /delta/,/delta/ /approx/ 0.1 - 0.2 giving rise to a superconducting rhombic phase and /delta/ /ge/ 0.5 resulting in crystallization of a semiconductor-like tetragonal phase. Copper ions in the YBa/sub 2/(Cu/sub 1-x/Fe/sub x/)/sub 3/O/sub 7-/delta//phases are known to occupy two non-equivalent sites, Cu(1) and Cu(2), having different coordination numbers. The polycrystalline YBa/sub 2/(Cu/sub 1-x/Fe/sub x/)/sub 5/O/sub 7-/delta// (x = 0.015) samples have been prepared by the known two-stage ceramic method from Y/sub 2/O/sub 3/, CuO, BaCO/sub 3/ and /alpha/-Fe/sub 2/O/sub 3/ (about 05% of /sup 57/Fe).