A new inorganic–organic hybrid: tetra­imid­azolium octa­molyb­date(VI) containing the β‐form of the [Mo8O26]4− anion

The title compound, (C₃H₅N₂)₄[β‐Mo₈O₂₆], has been prepared from imidazole octamolybdate, (C₃H₅N₂)₄[(C₃H₄N₂)₂(γ‐Mo₈O₂₆)], which was described previously. The γ→β conversion is produced in the presence of Cu(NO₃)₂·3H₂O and is reported for the first time in this work. The X‐ray structure analysis confirmed the presence of the [Mo₈O₂₆]^4? anion. The structure consists of β‐Mo₈O₂₆ polyanions and imidazolium cations. These cations are linked to the terminal and bridging O atoms of the anion by hydrogen bonds.     

Bis[diaquabis(2,2‐bipyridine N,N′‐dioxide‐κ2O,O′)cobalt(II)] ξ‐octamolybdate dihydrate

The title organic–inorganic hybrid compound, [Co(C₁₀H₈N₂O₂)₂(H₂O)₂]₂[Mo₈O₂₆]·2H₂O, consists of [Co(bpdo)₂(H₂O)₂]²⁺ (bpdo is 2,2‐bipyridine N,N′‐dioxide) and ξ‐[Mo₈O₂₆]⁴⁻ groups in a 2:1 ratio, plus two water solvent molecules. The independent Co atom in the cation is coordinated by four O atoms from two bpdo ligands and two water molecules, in a distorted octahedral geometry. The counter‐anions, built up around a symmetry center, are linked by solvent water molecules through O—H...O hydrogen bonds to generate two‐dimensional layers, which are in turn linked by coordinated water molecules from the cationic units through further O—H...O hydrogen bonds, forming a three‐dimensional supramolecular structure.     

[Cu(mim)4]2[α-Mo8O26] – A layer-type octamolybdate framework

By reaction of (NH₄)₆Mo₇O₂₄·4H₂O, Cu(NO₃)₂·2.5H₂O and 1-methylimidazole (mim) under hydrothermal conditions the novel copper molybdate [Cu(mim)₄]₂[α-Mo₈O₂₆] is obtained in the form of blue, rectangular-shaped crystals. The title compound crystallizes with monoclinic lattice symmetry in the space group P2₁/n. The predominant structural feature of the title compound is a two-dimensional framework that is constituted by [α-Mo₈O₂₆]^4?octamolybdate units as framework nods and the copper complex [Cu(mim)₄]²⁺ as a linker. In addition to single-crystal structure analysis [Cu(mim)₄]₂[α-Mo₈O₂₆] is characterized by powder diffraction as well as by FT-IR and UV–vis spectroscopy.     

1D Polyoxometalate‐based Inorganic‐Organic Hybrid Derived from ß‐Octamolybdate — Synthesis and Crystal Structure of [CoII(2, 2′‐bipy)2]2[Mo8O26]

A polyoxometalate‐based inorganic–organic hybrid compound [Co^II(2, 2′‐bpy)₂]₂[Mo₈O₂₆] ( 1 ) was synthesized by hydrothermal methods and structurally characterized by IR spectrum, TG analysis and X‐ray diffraction. The compound crystallizes in the monoclinic system, space group P2₁/n, a = 10.0681(2), b = 16.4467(2), c = 15.7838(3) Å, β = 100.046(1)°, V = 2573.52(8) ų, Z = 2. The structure of 1 is built up from β‐[Mo₈O₂₆]^4? subunits covalently linked via [Co^II(2, 2′‐bpy)₂]²⁺ fragments into a infinite 1D {[Co^II(2, 2′‐bpy)₂]₂[Mo₈O₂₆]}_∞ polymer.     

A New Organic‐Inorganic Charge‐transfer Salt [C15H17N4]4[Mo8O26] — Synthesis,Properties and Crystal Structure

A new organic donor 3‐amino‐6‐dimethylamino‐2‐methyl‐phenazine was introduced to charge‐transfer complex with polyoxometalate. The complex [C₁₅H₁₇N₄]₄[Mo₈O₂₆] ( 1 ) was synthesized by hydrothermal reaction of neutral red chloride (3‐amino‐6‐dimethylamino‐2‐methyl‐phenazine hydrochloride) and (NH₄)₆[Mo₇O₂₄] · 4H₂O and was characterized by EPR, element analysis and single crystal x‐ray diffraction.     

NC12H8(NH)2[Gd(N3C12H8)4] und [Gd(N3C12H8)3(N3C12H9)]·PhCN: Ein Beitrag zur Reaktivität und Kristallchemie homoleptischer Selten‐Erd‐Pyridylbenzimidazolate

NC₁₂H₈(NH)₂[Gd(N₃C₁₂H₈)₄] and [Gd(N₃C₁₂H₈)₃(N₃C₁₂H₉)]·PhCN: A Contribution to the Reactivity and Crystal Chemistry of Homoleptic Pyridylbenzimidazolates of the Rare Earth Elements Transparent colourless crystals of the compound NC₁₂H₈(NH)₂[Gd(N₃C₁₂H₈)₄] were obtained by solvent‐free reaction of gadolinium metal with molten 2‐(2‐Pyridyl)‐benzimidazole. Transparent yellow crystals of the compound [Gd(N₃C₁₂H₈)₃(N₃C₁₂H₉)]·PhCN were obtained by further reacting NC₁₂H₈(NH)₂[Gd(N₃C₁₂H₈)₄] with benzonitrile thermally. Both compounds exhibit homoleptic pure nitrogen coordinations of gadolinium, the PhCN ligand is not coordinating. Whilst NC₁₂H₈(NH)₂[Gd(N₃C₁₂H₈)₄] is salt like and consists of (NC₁₂H₈(NH)₂)⁺ and [Gd(N₃C₁₂H₈)₄]^— ions, [Gd(N₃C₁₂H₈)₃(N₃C₁₂H₉)]·PhCN has a molecular structure of uncharged [Gd(N₃C₁₂H₈)₃(N₃C₁₂H₉)] units.     

Two oxo complexes with tetra­nuclear [Fe4(μ3‐O)2]8+ and trinuclear [Fe3(μ3‐O)]7+ units

Two new oxo complexes, namely hexa‐μ₂‐acetato‐acetato­aquabis­(di‐3‐pyridylamine)di‐μ₃‐oxo‐tetra­iron(III) chloride mono­hydrate ethanol 1.25‐solvate, [Fe₄(C₂H₃O₂)₇O₂(C₁₀H₉N₃)₂(H₂O)]Cl·1.25C₂H₆O·H₂O, (I), containing a tetra­nuclear [Fe₄(μ₃‐O)₂]⁸⁺ unit, and 2‐methyl­imidazolium hexa‐μ₂‐acetato‐acetatodiaqua‐μ₃‐oxo‐triiron(III) chloride dihydrate, (C₄H₇N₂)[Fe₃(C₂H₃O₂)₇O(H₂O)₂]Cl·2H₂O, (II), with a trinuclear [Fe₃(μ₃‐O)]⁷⁺ unit, are presented. Both structures are formed by two well differentiated entities, viz. a compact isolated cluster composed of Fe^III ions coordinated to O²⁻ and CH₃CO₂⁻ anions, and an external group formed by a central Cl⁻ ion surrounded by different solvent groups to which the anion is bound through hydrogen bonding. In the case of (I), charge balance cannot be achieved within the groups, so the structure is macroscopically ionic; in the case of (II), in contrast, each group is locally neutral owing to the inter­nal compensation of charges. The trinuclear complex crystallizes with the metal cluster, chloride anion and 2‐methyl­imidazolium cation bisected by a crystallographic mirror plane.     

Polymeric diaqua(μ2‐2,2′‐bipyrimidinyl‐κ4N1,N1′:N3,N3′)‐di‐μ3‐hydroxy‐bis(μ5‐benzene‐1,3,5‐tricarboxylato‐κ5O1:O2:O3:O3:O5)tetracobalt(II) dihydrate

The structure of the title compound, [Co₄(C₉H₃O₆)₂(OH)₂(C₈H₆N₄)(H₂O)₂]·2H₂O, contains three separate species, namely the μ₅‐bridging C₉H₃O₆^3? anion, the doubly chelating and therefore μ₂‐bridging C₈H₆N₄ ligand (bi­pyrimidine, BPM), and the dihydrated di­aqua­di­hydroxy tetranuclear cationic cluster, [Co₄(OH^?)₂(H₂O)₂]⁶⁺·2H₂O, which lies on a crystallographic centre of symmetry, as does the BPM ligand with, in this case, the centre of symmetry coincident with the midpoint of the C—C bond joining the six‐membered rings. Within the cation cluster, the Co atoms of one pair are five‐coordinate and those of the other six‐coordinate.     

Molybdänhalogenidcluster mit sechs terminalen Alkoholatliganden: (C18H36N2O6Na)2[Mo6Cl8(OCH3)6] · 6CH3OH und (C18H36N2O6Na2)2[Mo6Cl8(OC6H5)6]

Molybdenum(II) Halide Clusters with six Alcoholate Ligands: (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OCH₃)₆] · 6CH₃OH and (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OC₆H₅)₆] . The reaction of Na₂[Mo₆Cl₈(OCH₃)₆] and 2,2,2-crypt yields (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OCH₃)₆] · 6 CH₃OH ( 1 ), which is converted to (C₁₈H₃₆N₂O₆Na)₂[Mo₆Cl₈(OC₆H₅)₆] ( 2 ) by metathesis with phenol. According to single crystal structure determinations ( 1 : P3 1c, a=14.613(3) Å, c=21.036(8) Å; 2 : P3 1c, a=15.624(1) Å, c=19.671(2) Å) the compounds contain anionic clusters [Mo₆Cl₈ⁱ(OR^a)₆]^2? ( 1 : d(Mo—Mo) 2.608(1) Å to 2.611(1) Å, d(Mo—Cl) 2.489(1) Å to 2.503(1) Å, d(Mo—O) 2.046(4) Å; 2 : d(Mo—Mo) 2.602(3) Å to 2.608(3) Å, d(Mo—Cl) 2.471(5) Å to 2.4992(5) Å, d(Mo—O) 2.091(14) Å). Electronic interactions of the halide cluster and the phenolate ligands in [Mo₆Cl₈(OC₆H₅)₆]^2? is investigated by means of UV/VIS spectroscopy and EHMO calculations.     

catena‐Poly[bis[tetraaquacobalt(II)‐μ‐4,4′‐bipyridine‐κ2N:N′] benzene‐1,2,4,5‐tetracarboxylate(4−) dihydrate]

The title compound, [Co(C₁₀H₈N₂)(H₂O)₄]₂(C₁₀H₂O₈)·2H₂O, consists of two crystallographically independent Co^II atoms linked by 4,4′‐bi­pyridine ligands into one‐dimensional chains, which are further connected into a three‐dimensional framework linked by [C₆H₂(COO)₄]^4? anions and water mol­ecules, achieved through complex hydrogen bonding.     

Two new soluble iron–oxo complexes: [Fe2(μ‐O)(μ‐O2CCF3)2(O2CCF3)2(C10H8N2)2] and [Fe4(μ3‐O)2(μ‐O2CCF3)6(O2CCF3)2(C10H8N2)2]·CF3CO2H

Two new iron–oxo clusters, viz. di‐μ‐tri­fluoro­acetato‐μ‐oxo‐bis­[(2,2′‐bi­pyridine‐κ²N,N′)(tri­fluoro­acetato‐κO)­iron(III)], [Fe₂O(CF₃CO₂)₄(C₁₀H₈N₂)₂], and bis(2,2′‐bi­pyridine)­di‐μ₃‐oxo‐hexa‐μ‐tri­fluoro­acetato‐bis­(tri­fluoro­acetato)­tetrairon(III) tri­fluoro­acetic acid solvate, [Fe₄O₂(CF₃CO₂)₈(C₁₀H₈N₂)₂]·CF₃CO₂H, contain dinuclear and tetranuclear Fe^III cores, respectively. The Fe^III atoms are in distorted octahedral environments in both compounds and are linked by oxide and tri­fluoro­acetate ions. The tri­fluoro­acetate ions are either bridging (bidentate) or coordinated to the Fe^III atoms via one O atom only. The fluorinated peripheries enhance the solubility of these compounds. Formal charges for all the Fe centers were assigned by summing valences of the chemical bonds to the Fe^III atom.     

Luminescent properties of three structures built from 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate and cadmium

Yellow–orange tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) dihydrate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·2H₂O, (I), and yellow tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) 1,4‐dioxane solvate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·C₄H₈O₂, (II), contain centrosymmetric mononuclear Cd²⁺ coordination complex molecules in different conformations. Dark‐red poly[[decaaquabis(μ₂‐3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κ²N:N′)bis(μ₂‐3‐cyano‐4‐dicyanomethylene‐1H‐pyrrole‐2,5‐diolato‐κ²N:N′)tricadmium] hemihydrate], [Cd₃(C₈HN₄O₂)₂(C₈N₄O₂)₂(H₂O)₁₀]·0.5H₂O, (III), has a polymeric two‐dimensional structure, the building block of which includes two cadmium cations (one of them located on an inversion centre), and both singly and doubly charged anions. The cathodoluminescence spectra of the crystals are different and cover the wavelength range from UV to red, with emission peaks at 377 and 620 nm for (III), and at 583 and 580 nm for (I) and (II), respectively.     

Koordinationspolymere 1, 2‐Dithiooxalato‐ und 1, 2‐Dithioquadratato‐Komplexe. Synthese und Strukturen von [BaCr2(bipy)2(1, 2‐dtox)4(H2O)2], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)2(H2O)2]·2H2O und [H3O][H5O2][Cu(cyclam)]3[Cu2(1, 2‐dtsq)3]2

Coordination Polymeric 1, 2‐Dithiooxalato and 1, 2‐Dithiosquarato Complexes. Syntheses and Structures of [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H2₂, and [H₃O][H₅O₂][Cu(cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ 1, 2‐Dithioxalate and 1, 2‐dithiosquarate ions have a pair of soft and hard donor centers and thus are suited for the formation of coordination polymeric complexes containing soft and hard metal ions. The structures of four compounds with building blocks containing these ligands are reported: In [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂] Barium ions and pairs of Cr(bipy)(1, 2‐dtox)₂ complexes form linear chains by the bisbidentate coordination of the dithiooxalate ligands towards Ba²⁺ and Cr³⁺. In [Ni(cyclam)(1, 2‐dtsq)]·2DMF short NÖH···O hydrogen bonds link the NiS₂N₄‐octahedra with C_2v‐symmetry to an infinite chain. In [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H₂O the 1, 2‐dithiosquarato ligand shows a rare example of S‐coordination towards manganese(II). The sulfur atoms of cis‐MnO₂S₄‐polyedra are weakly coordinated towards the axial sites of square‐planar NiN₄‐centers, thus forming a zig‐zag‐chain of Mn···Ni···Mn···Ni polyhedra. [H₃O][H₅O₂][Cu (cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ contains square planar [Cu^II(cyclam)]²⁺ ions and dinuclear [Cu^I₂(1, 2‐dtsq)₃]^4— ions. Here each copper atom is trigonally planar coordinated by S‐donor atoms of the ligands. The Cu…Cu distance is 2.861(4)Å.     

Two tetranuclear zinc clusters, [Zn4(μ3‐OEt)2(μ2‐MalO)4Et2] and [Zn4(μ3‐GueO)2(μ2‐GueO)2(μ2‐MalO)2(MalO)2]·2C7H8, containing defective dicubane core geometries (MalOH is maltol and GueOH is guethol)

The zinc alkoxide molecules in di‐μ₃‐ethanolato‐diethyltetrakis(μ₂‐2‐methyl‐4‐oxo‐4H‐pyran‐3‐olato‐κ³O³,O⁴:O³)tetrazinc(II), [Zn₄(C₂H₅)₂(C₂H₅O)₂(C₆H₅O₃)₄], (I), and bis(μ₃‐2‐ethoxyphenolato‐κ⁴O¹,O²:O¹:O¹)bis(μ₂‐2‐ethoxyphenolato‐κ³O¹,O²:O¹)bis(μ₂‐2‐methyl‐4‐oxo‐4H‐pyran‐3‐olato‐κ³O³,O⁴:O³)bis(2‐methyl‐4‐oxo‐4H‐pyran‐3‐olato‐κ²O³,O⁴)tetrazinc(II) toluene disolvate, [Zn₄(C₆H₅O₃)₄(C₈H₉O₂)₄]·2C₇H₈, (II), lie on crystallographic centres of inversion. The asymmetric units of (I) and (II) contain half of the tetrameric unit and additionally one molecule of toluene for (II). The Zn^II atoms are four‐ and six‐coordinated in distorted tetrahedral and octahedral geometries for (I), and six‐coordinated in a distorted octahedral environment for (II). The Zn^II atoms in both compounds are arranged in a defect dicubane Zn₄O₆ core structure composed of two EtZnO₃ tetrahedra and ZnO₆ octahedra for (I), and of four ZnO₆ octahedra for (II), sharing common corners. The maltolate ligands exist mostly in a μ₂‐bridging mode, while the guetholate ligands prefer a higher coordination mode and act as μ₃‐ and μ₂‐bridges.     

IV Dodekaedrische [Mo(CN)8]‐Koordination in den cyanoverbrückten Cobalt‐ und Nickel‐Amminkomplexen MII2(NH3)8[Mo(CN)8] · 1,5 H2O (MII = Co,Ni) und Ni2(NH3)9[Mo(CN)8] · 2 H2O

Crystal Structures of Octacyanomolybdates(IV). IV Dodecahedral [Mo(CN)₈] Coordination of the Cyano‐Bridged Cobalt and Nickel Ammin Complexes M^II₂(NH₃)₈[Mo(CN)₈] · 1.5 H₂O (M^II = Co, Ni) and Ni₂(NH₃)₉[Mo(CN)₈] · 2 H₂O At single crystals of the hydrated cyano complexes Co₂(NH₃)₈[Mo(CN)₈] · 1.5 H₂O (a = 910.0(4), b = 1671(2), c = 1501(1) pm, β = 93.76(6)°) and Ni₂(NH₃)₈[Mo(CN)₈] · 1.5 H₂O (a = 899.9(9), b = 1654.7(4), c = 1488(1) pm, β = 94.01°), isostructurally crystallizing in space group P2₁/c, Z = 4, and of trigonal Ni₂(NH₃)₉[Mo(CN)₈] · 2 H₂O (a = 955.1(1), c = 2326.7(7) pm, P3₁, Z = 3), X‐ray structure determinations were performed at 168 resp. 153 K. The [Mo(CN)₈]^4– groups of the three compounds, prepared at about 275 K and easily decomposing, show but slightly distorted dodecahedral coordination (mean distances Mo–C: 216.3, 215.4 and 216.1 pm). Within the monoclinic complexes the anions twodimensionally form cyano bridges to the ammin cations [M(NH₃)₄]²⁺ and are connected with the resulting [MN₆] octahedra (Co–N: 215.1 pm, Ni–N: 209.8 pm) into strongly puckered layers. The trigonal complex exhibits a chain structure, as one [Ni(NH₃)₅]²⁺ cation is only bound as terminal octahedron (Ni–N: 212.0 pm). Details and the influence of hydrogen bridges are discussed.     

Di­aqua­bis(1,10‐phenanthroline‐κ2N,N′)­manganese(II) thiodiglycolate bis(1,10‐phenanthroline‐κ2N,N′)(thiodiglycolato‐κ2O,O′)­manganese(II) tridecahydrate

The title compound, [Mn(C₁₂H₈N₂)₂(H₂O)₂](C₄H₄O₄S)·[Mn(C₄H₄O₄S)(C₁₂H₈N₂)₂]·13H₂O, contains one dianion of thio­diglycolic acid (tdga²⁻) and two independent man­ganese(II) moieties, viz. [Mn(phen)₂(H₂O)₂]²⁺ and [Mn(tdga)(phen)₂], where phen is 1,10‐phenanthroline. The Mn^II atoms are octahedrally coordinated by four N atoms of two bidentate phen ligands [Mn—N = 2.240 (2)–2.3222 (19) Å] and either two water O atoms or two tdga carboxyl O atoms [Mn—O = 2.1214 (17)–2.1512 (17) Å]. The tdga ligand chelates as an O,O′‐bidentate ligand, forming an eight‐membered ring with one Mn atom. The free tdga²⁻ dianion is hydrogen bonded to an [Mn(phen)₂(H₂O)₂]²⁺ ion, with O⋯O distances of 2.606 (2) and 2.649 (2) Å. The crystal structure is further stabilized by an extensive network of hydrogen bonds involving 13 water mol­ecules.     

[μ‐1κ2O,O′:2(η5)‐Cyclopentadienylcarboxylato][2(η5)‐diphenylphosphinocyclopentadienyl]bis[1,1(η5)‐tetramethylcyclopentadienyl]iron(II)titanium(III)

Reacting stoichiometric amounts of 1‐(diphenylphosphino)ferrocene­carboxylic acid and [Ti(η⁵‐C₅HMe₄)₂(η²‐Me₃SiC[triple‐bond]CSiMe₃)] produced the title carboxyl­atotitanocene complex, [{μ‐1κ²O,O′:2(η⁵)‐C₅H₄CO₂}{2(η⁵)‐C₅H₄P(C₆H₅)₂}{1(η⁵)‐C₅H(CH₃)₄}₂Fe^IITi^III] or [FeTi(C₉H₁₃)₂(C₆H₄O₂)(C₁₇H₁₄P)]. The angle subtended by the Ti/O/O′ plane, where O and O′ are the donor atoms of the κ²‐carboxy­late group, and the plane of the carboxyl‐substituted ferrocene cyclo­penta­dienyl is 24.93 (6)°.     

Bis(acesulfamato‐κ2N3,O4)bis­(2‐amino­pyrimidine‐κN1)copper(II)

In the crystal structure of the title compound, bis­(2‐amino­pyrimidine‐κN¹)bis­[6‐meth­yl‐1,2,3‐oxathia­zin‐4(3H)‐one 2,2‐dioxide(1−)‐κ²N³,O⁴]copper(II), [Cu(C₄H₄NO₄S)₂(C₄H₅N₃)₂], the first mixed‐ligand complex of acesulfame, the Cu^II centre resides on a centre of symmetry and has an octa­hedral geometry that is distorted both by the presence of four‐membered chelate rings and by the Jahn–Teller effect. The equatorial plane is formed by the N atoms of two amino­pyrimidine (ampym) ligands and by the weakly basic carbonyl O atoms of the acesulfamate ligands, while the more basic deprotonated N atoms of these ligands are in the elongated axial positions with a strong misdirected valence. The crystal is stabilized by pyrimidine ring stacking and by inter­molecular hydrogen bonding involving the NH₂ moiety of the ampym ligand and the carbon­yl O atom of the acesulfamate moiety.     

Coordination Chemistry of [Nb2(S2)2]4+ Clusters: Preparation and Crystal Structures of K4[Nb2(S2)2(C2O4)4] · 6 H2O and (NH4)6[Nb2(S2)2(C2O4)4](C2O4)

Bis(disulfido)bridged Nb^IV cluster oxalate complexes [Nb₂(S₂)₂(C₂O₄)₄]^4– were prepared by ligand substitution reaction from the aqua ion [Nb₂(μ‐S₂)₂(H₂O)₈]⁴⁺ and isolated as K₄[Nb₂(S₂)₂(C₂O₄)₄] · 6 H₂O ( 1 ), (NH₄)₆[Nb₂(S₂)₂(C₂O₄)₄](C₂O₄) ( 2 ) and Cs₄[Nb₂(S₂)₂(C₂O₄)₄] · 4 H₂O ( 3 ). The crystal structures of 1 and 2 were determined. The crystals of 1 belong to the space group P1, a = 720.94(7) pm, b = 983.64(10) pm, c = 1071.45(10) pm, α = 109.812(1)°, β = 91.586(2)°, γ = 105.257(2)°. The crystals of 2 are monoclinic, space group C2/c, a = 1567.9(2) pm, b = 1906.6(3) pm, c = 3000.9(4) pm, β = 95.502(2)°. The packing in 2 shows alternating layers of cluster anions and of ammonium/uncoordinated oxalates perpendicular to the [1 0 1] direction. Vibration spectra, electrochemistry and thermogravimetric properties of the complexes are also discussed.     

The regioisomeric 1H(2H)‐pyrazolo[3,4‐d]pyrimidine N1‐ and N2‐(2′‐deoxy‐β‐D‐ribofuranosides)

In the title regioisomeric nucleosides, alternatively called 1‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₁₀H₁₂N₄O₃, (II), and 2‐(2‐deoxy‐β‐d ‐erythro‐furan­osyl)‐2H‐pyrazolo­[3,4‐d]pyrimidine, C₁₀H₁₂N₄O₃, (III), the conformations of the gly­cosyl­ic bonds are anti [?100.4 (2)° for (II) and 15.0 (2)° for (III)]. Both nucleosides adopt an S‐type sugar pucker, which is C2′‐endo‐C3′‐exo (²T₃) for (II) and 3′‐exo (between ₃E and ⁴T₃) for (III).