Rhenium(IV) cyanate complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReBr4(OCN)(DMF)] and (NBu4)2[ReBr(OCN)2(NCO)3]

Two new rhenium(IV) mononuclear compounds of formula NBu₄[ReBr₄(OCN)(DMF)] (1) and (NBu₄)₂[ReBr(OCN)₂(NCO)₃] (2) (NBu₄ = tetrabutylammonium cation, OCN = O-bonded cyanate anion, NCO = N-bonded cyanate anion and DMF = N,N-dimethylformamide) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 crystallizes in the monoclinic system with the space group P2₁/n, whereas 2 crystallizes in the triclinic one with as space group. In both complexes the rhenium atom is six-coordinated, in 1 by four Br atoms in the equatorial plane, and two trans-oxygen atoms, one of a DMF molecule and another one from a cyanato group, while in 2 by one bromide anion and five cyanate ligands, two of which are O-bonded and three N-bonded, forming a somewhat distorted octahedral surrounding. Magnetic susceptibility measurements on polycrystalline samples of 1 and 2 in the temperature range 1.9-300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field splitting (|2D| is ca. 41.6 and 39.2 cm⁻¹ for 1 and 2, respectively).     

Carboxylate and dicarboxylate derivatives of [Et4N][Re2(CO)6(OR)3] (R = H or Me)

The ligand exchange reaction of the anionic binuclear rhenium complexes (R = H (1) or Me (2)) has been studied with the carboxylic acids; benzoic acid (3, 4, and 5), fumaric acid (6), and terephthalic acid (7). The exchange with benzoic acid can be controlled by stoichiometry to one, two, or three substitutions. The doubly (4) and triply (5) substituted complexes represent new structural motifs for the triply bridged Re₂(CO)₆ unit. The dicarboxylic acids fumaric and terephthalic bridge two dirhenium centers. Crystal structure determinations have been carried out for the new complexes synthesized.     

Synthesis and characterization of new AMTTO-imine-ligands and their silver(I) complexes: crystal structures of TAMTTO, [Ag2(TAMMTO)4](NO3)2 · 4MeOH, [Ag(TAMTTO)(PPh3)2]NO3 · 1.5THF, [Ag(FAMTTO)(PPh3)2]NO3

Reaction of 4-amino-6-methyl-1,2,4-triazin-thione-5-one (AMTTO, 1) with 2-thiophenecarboxaldehyde and 2-furaldehyde led to the corresponding iminic compounds 6-methyl-4-[thiophene-2-yl-methylene-amino]-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (TAMTTO, 2) and 4-[furan-2-yl-methylene-amino]-6-methyl-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (FAMTTO, 3). Treatment of 2 with AgNO₃ gave the complex [Ag₂(TAMMTO)₄](NO₃)₂ · 4MeOH (4) and of 2 and 3 with [Ag(PPh₃)₂]NO₃ gave the complexes [Ag(TAMTTO)(PPh₃)₂]NO₃ · 1.5THF (5) and [Ag(FAMTTO)(PPh₃)₂]NO₃ (6), respectively. All the compounds have been characterized by elemental analyses, IR spectroscopy and mass spectrometry. Compound 2 and all the complexes have been characterized by X-ray diffraction studies, respectively. In addition, 5 and 6 have been characterized by ³¹P NMR spectroscopy. Crystal data for 2 at −80 °C: monoclinic, space group C2/c, a=2319.6(2), b=609.8(1), c=1673.6(2) pm, β=106.14(1)°, Z=8, R₁=0.0523; for 4 at −80 °C: triclinic, space group , a=877.6(1), b=1085.2(1), c=1557.7(2) pm, α=77.14(1)°, β=80.87(1)°, γ=78.18(1)°, Z=1, R₁=0.0407; for 5 at 20 °C: triclinic, space group , a=1151.1(2), b=1225.1(2), c=1887.4(3) pm, α=78.04(1)°, β=86.20(1)°, γ=76.03(1)°, Z=2, R₁=0.0662; for 6 at −80 °C: triclinic, space group , a=1189.7(2), b=1387.8(2), c=1410.9(2) pm, α=94.74(2)°, β=95.12(2)°, γ=112.41(2)°, Z=2, R₁=0.0511.     

Synthesis, characterization and X-ray structure of several aryloxide and alkoxide derivatives of [Et4N][Re2(CO)6(OR)3] (R = H or Me)

The ligand exchange reaction of the anionic binuclear rhenium complexes (R = H (1) or Me (2)) has been studied with the arylalcohols 4-aminophenol (3, 4), 3-dimethylaminophenol (5), 3-cyanophenol (6) and 4-cyanophenol (7, 8) and the diol ethylene glycol (9). Complete exchange of the three hydroxy or methoxy ligands by aryl alcohols can be attained by heating the reaction mixture or allowing the mixture to stir for several days. Incomplete exchange is achieved by stoichiometric control of the incoming ligand and is complete within twelve hours. For the alkyl alcohol ethylene glycol complete exchange can be obtained in 8 h. Crystal structure determinations for several of these derivatives have been carried out.     

Solid state coordination chemistry of molybdenum oxides with 1,2,3-triazole (Htrz): The crystal structures of [Cu(I)Cu(II)2(trz)2Mo4O13(OH)], [MoO3(Htrz)0.5] and [Cu(I)trz]

Hydrothermal chemistry was used to prepare the bimetallic organic-inorganic hybrid oxide [Cu(I)Cu(II)₂(trz)₂Mo₄O₁₃(OH)] · 6H₂O (1 · 6H₂O). The structure consists of chains linked through into a three-dimensional framework. The structures of the simple metal-triazole phases [MoO₃(Htrz)_0.5] (2) and [Cu(trz)] (3) are also reported. Compound 2 is two-dimensional, constructed from corner-sharing {MoO₅N} octahedra. Compound 3 consists of {Cu(trz)}_n chains linked through weak Cu?Cu contacts into a virtual layer.     

A trinuclear copper(II) complex with 2,5-pyridine-dicarboxylato bridges - [Cu3(2,5-pydc)2(Me5dien)2(H2O)2(BF4)2] · H2O: Synthesis, crystal structure and magnetic properties

A trinuclear copper(II) complex, [Cu₃(2,5-pydc)₂(Me₅dien)₂(BF₄)₂(H₂O)₂] · H₂O 1, has been constructed from 2,5-pyridine-dicarboxylato bridges (2,5-pydc²⁻) and N,N,N′,N″,N″-pentamethyl-diethylenetriamine (Me₅dien) acting as a blocking ligand. The copper ions, within the centrosymmetric trinuclear cations, are connected by two 2,5-pydc²⁻ bridges, with an intramolecular Cu···Cu separation of 8.432 Å. The central copper ion exhibits an elongated octahedral geometry, with semicoordinated ions, while the terminal ones are pentacoordinated (distorted square-pyramidal geometry). The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the copper(II) ions (J = −5.9 cm⁻¹, H = −JS_Cu1S_Cu2 − JS_Cu2S_Cu1a).     

Two cyano-bridged heterotrinuclear complexes built from [(Tp)Fe(CN)3] (Tp = hydrotris(pyrazolyl)borate): synthesis, crystal structures and magnetic properties

Using an anionic precursor [(Tp)Fe^III(CN)₃]⁻ (1) as a building block, two cyano-bridged centrosymmetric heterotrinuclear complexes, (2) and (3) (en = ethylenediamine), have been synthesized and structurally characterized. In each complex, [TpFe(CN)₃]⁻ acts as a monodentate ligand toward a central [Mn(C₂H₅OH)₄]²⁺ or [Ni(en)₂]²⁺ core through one of its three cyanide groups, the other two cyanides remaining terminal. The intramolecular Fe-Mn and Fe-Ni distances are 5.2354(4) and 5.0669(11) Å, respectively. The magnetic properties of complexes 2 and 3 have been investigated in the temperature range of 2.0-300 K. A weak antiferromagnetic interaction between the Mn(II) and Fe(III) ions has been found in complex 2. The magnetic data of 2 can be fitted with the isotropic Hamiltonian: where J and J′ are the intramolecular exchange coupling parameters between adjacent and peripheral spin carriers, respectively. This leads to values of J = −1.37 cm⁻¹ and g = 2.05. The same fitting method is applied to complex 3 to give values of J = 1.2 cm⁻¹ and g = 2.25, showing that there is a ferromagnetic interaction between the Fe(III) and Ni(II) ions.     

Transition metal halide salts of 8-methylquinolinium: Synthesis and structures of (8-methylquinolinium)2 MX4·nH2O (M = Cu, Co, Zn; X = Cl, Br; n = 0, 1)

The reactions of metal(II) chlorides and bromides with 8-methylquinoline (8-mequin) in neutral and acidic solutions were investigated. The reaction with ZnCl₂, ZnBr₂, CoCl₂, CoBr₂, CuCl₂ or CuBr₂ with the appropriate HX in water or aqueous ethanol gave complexes of the formula (8-mequin)₂MX₄ (1, M = Cu, X = Cl; 2, M = Cu, X = Br; 3, M = Co, X = Cl; 4, M = Co, X = Br) or (8-mequin)₂ZnX₄·nH₂O (5, X = Cl, n = 0; 6, X = Br, n = 0; 7, X = Cl, n = 1; 8, X = Br, n = 1). Crystals of 1, 2 and 4-8 suitable for single crystal X-ray diffraction were obtained and the structures reported. Compounds 1 and 2 crystallize in the monoclinic space group C2/c, while 4-8 crystallize in the triclinic space group, . Variable temperature magnetic susceptibility data indicate very weak interactions for the copper compounds 1 and 2, while the magnetic behavior of 3 and 4 is dominated by single ion anisotropy, with weaker antiferromagnetic interactions.     

Polymorphism in intercluster salt system: two crystal structures of [Al13O4(OH)24(H2O)12][H2W12O40](OH) · nH2O

In this paper, we report the syntheses and crystal structures of two intercluster salt compounds, [Al₁₃O₄(OH)₂₄(H₂O)₁₂][H₂W₁₂O₄₀](OH) · 20H₂O (1) and [Al₁₃O₄(OH)₂₄(H₂O)₁₂][H₂W₁₂O₄₀](OH) · 24H₂O (2). The crystal structures of these compounds show that they are polymorphs to each other with different modes of packing of the and ions. The structures of 1 and 2 can be described as alternating arrangements of ionic clusters that optimize electrostatic interactions and hydrogen bonds between them. The structure of 1 is analogous to the PtS structure and that of 2 is similar to the β-BeO structure with the clusters forming tetrahedral or square planar coordination geometries to each other.     

Syntheses and crystal structures of cyano-bridged cluster-metal layered coordination polymers [Cu(dien)]3[W4Te4(CN)12] · 9H2O and [Ni(en)(NH3)]3[W4Se4(CN)12] · 7.5H2O

Two new tetrahedral tungsten cyanide cluster compounds, [Cu(dien)]₃[W₄Te₄(CN)₁₂] · 9H₂O (1) (dien=diethylenetriamine) and [Ni(en)(NH₃)]₃[W₄Se₄(CN)₁₂] · 7.5H₂O (2) (en=ethylenediamine), were synthesized by treating aqueous solutions of the saltlike cluster compound K₆[W₄Te₄(CN)₁₂] · 5H₂O/K₆[W₄Se₄(CN)₁₂] · 6H₂O with copper(II)/nickel(II) chloride in aqueous ammonia containing dien/en. The cyano-bridged layered coordination polymeric compounds were characterized by single-crystal X-ray diffraction analysis: monoclinic, space group P2₁ for 1; trigonal, space group for 2. Structures of 1 and 2 consist of infinite neutral layers of cluster components {W₄Te₄(CN)₁₂}/{W₄Se₄(CN)₁₂} connected, one another by {Cu(dien)} or {Ni(en)(NH₃)} fragments, respectively.     

Benzimidazole derivatives as NSO ligands for the fac-[M(CO)3] (M = Re, Tc)

Two rhenium(I) tricarbonyl complexes with the tridentate monoanionic NSO ligands, 4-(benzimidazol-2-yl)-3-thiabutanoic acid (complex 3) and [1-(11-carboxyundecanyl)-4-(benzimidazol-2-yl)]-3-thiabutanoic acid (complex 4) were synthesized and characterized by spectroscopic methods and elemental analysis. X-ray crystallographic analysis of complex 3 revealed a distorted octahedral geometry around rhenium defined by the three facially bound CO groups and the NSO donor atom set of the tridentate ligand. The analogous technetium-99m complexes (complexes 5 and 6) were also prepared quantitatively by reaction of the NSO ligands with the fac-[^99mTc(H₂O)₃(CO)₃]⁺ synthon and their identity was established by chromatographic comparison to their rhenium congeners. Biodistribution in mice of complex 6 bearing the fatty acid chain showed significant heart uptake (6.26 ± 0.79% ID/g p.i.) at 1 min accompanied, however, with a heart:blood ratio below 1.     

Novel long bipyridine-type linking ligands containing an intervening naphthalene fragment: [Zn(L)(NO3)2], [Zn(L)(NO3)2], and [Cd(L)1.5(NO3)2] (L = (4-py)-CHN-C10H6-NCH-(4-py); L = (3-py)-CHN-C10H6-NCH-(3-py))

Novel bipyridine-type linking ligands L¹ ((4-py)-CHN-C₁₀H₆-NCH-(4-py)) and L² ((3-py)-CHN-C₁₀H₆-NCH-(3-py)), a pair of isomers due to possessing different pairs of terminal pyridyl groups, were prepared by the Schiff-base condensation. In ligand L¹, the N?N separation between the terminal pyridyl groups is 16.0 Å, with their nitrogen donor atoms at the para positions (4,4′). The corresponding N?N separation in ligand L² is 14.2 Å, with the nitrogen donor atoms at the meta positions (3,3′). 1-D zigzag-chain coordination polymers [Zn(L¹)(NO₃)₂] (1) and [Zn(L²)(NO₃)₂] (2) were prepared by reactions of Zn(NO₃)₂ · 6H₂O with ligands L¹ and L², respectively, by solution diffusion. Polymer 3, [Cd(L¹)_1.5(NO₃)₂], prepared from Cd(NO₃)₂ · 4H₂O and L¹, exhibits a 1-D ladder structure, whose repeating ladder unit consists of four Cd metals and four L¹ ligands to create a large 76-membered ring with dimensions of 20.8 × 20.8 Å. All products were structurally characterized by X-ray diffraction.     

Synthesis and structures of bimetallic silicon-containing imido alkylidene complexes of molybdenum Me2Si[CHMo(NAr)(ORF3)2]2 and PhVinSi[CHMo(NAr)(ORF3)2]2

Bimetallic alkylidene complexes of molybdenum (R_F3O)₂(ArN)MoCH-SiMe₂-CHMo(NAr)(OR_F3)₂ (1) and (R_F3O)₂(ArN)MoCH-SiPhVin-CHMo(NAr)(OR_F3)₂ (2) (Ar = 2,6-C₆H₃; R_F3 = CMe₂CF₃) have been prepared by the reactions of vinyl silicon reagents Me₂Si(CHCH₂)₂ and PhSi(CHCH₂)₃ with known alkylidene compound PhMe₂C-CHMo(NAr)(OR_F3)₂. Complexes 1 and 2 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1 and 2 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and predominant cis-units content in the case of 2.     

Lanthanide iodides as promoters of acetonitrile amination. Molecular structure of MeC(NH)NHPr, MeC(NH)NHBu and {Dy[MeC(NH)NEt2]6}I3

Amination of acetonitrile by the amines MeNH₂, PrⁿNH₂, PrⁱNH₂, Bu^tNH₂, and Et₂NH is efficiently promoted by the lanthanide iodides LnI₂ (Ln = Nd, Dy, Tm), LnI₃ (Ln = Pr, Nd, Dy) and LnI₃(THF)₃ (Ln = Pr, Nd, Dy). The formed mono- and N,N′-disubstituted amidines MeC(NH)NHR (R = Prⁱ, Bu^t), MeC(NH)NEt₂, MeC(NR)NHR (R = Me, Prⁿ) were isolated mainly as the complexes with starting iodide of general composition LnI₂(amidine)_x (1) or LnI₃(amidine)_x (2) (x = 3-8). In the products 1, which evidently are the mixtures of LnI²⁺, and LnI₃ derivatives, the metal exists in trivalent state but one of the ligands actually is amidinate anion. A part of the generated amidines remains in the reaction solutions in free form. Heating of the 1 and 2 in vacuum at 150-200 °C affords corresponding amidine and the complexes with reduced amount of the amidine ligands LnI₂(amidine)_y (3) or LnI₃(amidine)_y (4) (y = 2-3). The products 3 and 4 displayed the same catalytic activity in the acetonitrile-amine cross-coupling as the initial iodides. SmI₂ and especially YbI₂ revealed lower activity. The structure of isopropylacetamidine (5), tert-butylacetamidine (6) and {Dy[MeC(NH)NEt₂]₆}I₃(MeCN) (7) were determined by X-ray diffraction analysis.     

Synthesis and characterization of cis-[(PPh3)2Pt{9-MeAd(-H),NN}]X (X = NO3, PF6): The first example of a platinum(II) complex containing the N,N-chelated 9-methyladenine anion

Reaction between the binuclear hydroxo complex cis-[(PPh₃)₂Pt(μ-OH)]₂X₂ (X⁻ = NO₃, 1a; , 1b) and the model DNA base 9-methyladenine (9-MeAd) leads to the formation of the mononuclear species cis-[(PPh₃)₂Pt{9-MeAd(-H),N⁶N⁷}]X (X⁻ = NO₃, 2a; PF₆, 2b), in which the nucleobase chelates the Pt(II) ion with the N6 and N7 atoms. The coordination mode of the nucleobase has been determinated through a multinuclear (¹H, ³¹P, ¹³C, ¹⁵N and ¹⁹⁵Pt) NMR analysis and the nuclearity of the complex has been obtained by E.S.I. mass spectrometry. 2 represents the first example of an isolated platinum complex in which the NH₂-deprotonated adenine exhibits this binding mode.     

Formation and stabilization of five-coordinate iron(II) verdoheme analogues by axial weakly coordinating anion ligation. X-ray crystal structures of [(OEOPFe)2O](X)2 (X = AsF6, SbF6)

The effect of weakly coordinating anions, , as axial ligands on the formation and coordination chemistry of verdoheme analogues have been examined. Two new five-coordinate and stable iron(II) verdoheme analogues, [OEOPFe^IIX], where OEOP is the monoanion of octaethyloxoporphyrin and X = AsF₆ and SbF₆, have been isolated. The compounds have been characterized by different spectroscopic methods as well as elemental analysis. ¹H NMR spectroscopy and magnetic moment measurements show that the [OEOPFe^IIX] are paramagnetic and iron is five-coordinate. Exposure of dichloromethane solutions of [OEOPFe^IIX] (X = AsF₆ (2), SbF₆ (3)) to dioxygen result in their transformation into the μ-oxo bridged compounds, [(OEOPFe)₂O](X)₂ (X = AsF₆ (4), SbF₆ (5)). The structures of 4 and 5 have been determined by X-ray diffraction analysis, both are structurally similar with a P2₁/c space group in the monoclinic crystal system.     

Synthesis and characterization of isopropylamine complexes of lanthanide(II) diiodides: Molecular structure of TmI2(PrNH2)4 and EuI2(PrNH2)4

It was found that the lanthanide diiodides LnI₂ (1) (Ln = Nd, Sm, Eu, Dy, Tm, Yb) are dissolved in isopropylamine (IPA) without redox transformations. Stability of the formed solutions decreases in a row Eu ≈ Yb > Sm > Tm > Dy > Nd. Removing of a solvent in vacuum leaves complexes LnI₂(IPA)_x (2) (Nd, x = 5; Sm, Eu, Dy, Tm, Yb, x = 4) as crystalline colored solids. Stability of 2-Nd,Dy,Tm is higher than that of known THF or DME coordinated salts. Divalent state of metal in the products is confirmed by data of UV-Vis spectroscopy, magnetic measurements and their chemical behavior. Structure of 2-Eu and 2-Tm was established by X-ray diffraction analysis. Oxidation of 2-Nd,Dy in IPA affords amine-amides (PrⁱNH)Ln(IPA)_y (3) (Nd, y = 4; Dy, x = 3). n-Propylamine also dissolves the iodides 1-Sm,Eu,Dy,Tm,Yb but stability of the solutions is significantly lower. 1-Nd vigorously reacts with PrⁿNH₂ even at −30 °C which hampers the formation of the solution.     

Metallocycle and ring-opening polymerization of silver(I) complexes with 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene ligand

The reaction of 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag₂(bib)₂](NO₃)₂ · 2H₂O, in which bib ligand displayed in cis configuration. When the additional competing ligands/counterions, such as oxlate salt, 1,2-diaminoethene (en), 1,3-diaminopropane (pn), and were introduced, respectively, to the above-mentioned reaction solution, ring-open polymerization of sliver(I) complexes {[Ag(bib)]NO₃ · H₂O}_n (1), {[Ag(bib)₂]X}_n ( (2), (3)), {[Ag₂(bib)₂(NO₂)](NO₂) · 19/8H₂O}_n (4) and {[Ag₂(bib)₂](V₄O₁₂)_0.5 · 3H₂O · 2MeCN}_n (5) were generated. In compounds 1, 4 and 5, bib ligand adopts trans configuration and twists around the Ag-Ag axis, giving rise to single-stranded helical structure with short adjacent Ag?Ag distances of 3.56, 3.56, 3.50 and 3.63 Å, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag₂(bib)₂]²⁺, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag?Ag distances of 8.52 Å in 2 and 8.61 Å in 3 along with the strong intracyclicπ-π interactions between phenyl groups. Cis and trans configurations of bib coexist in solution and crystallize in complexes 1 and 2 in the solid state in the presence of en or pn. The solution of 1 and 2 can be converted into 3 via the addition of the bulky counter anion or into 4 through introduction of the competing ligand/conuterion .     

Structural analysis and magnetic properties of the copper(II) dicyanamide complexes [Cu2(dmphen)2(dca)4], [Cu(dmphen)(dca)(NO3)]n and [Cu(4,4-dmbpy)(H2O)(dca)2] (dca=dicyanamide; dmphen=2,9-dimethyl-1,10-phenanthroline; 4,4-dmbpy=4,4-dimethyl-2,2-bipyridine)

The preparation, crystal structures and magnetic properties of three copper(II) compounds of formulae [Cu₂(dmphen)₂(dca)₄] (1), [Cu(dmphen)(dca)(NO₃)]_n (2) and [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] (3) (dmphen=2,9-dimethyl-1,10-phenanthroline, dca=dicyanamide and 4,4^′-dmbpy=4,4^′-dimethyl-2,2^′-bipyridine) are reported. The structure of 1 consists of discrete copper(II) dinuclear units with double end-to-end dca bridges whereas that of 2 is made up of neutral uniform copper(II) chains with a single symmetrical end-to-end dca bridge. Each copper atom in 1 and 2 is in a distorted square pyramidal environment: two (1) or one (2) nitrile-nitrogen atoms from bridging dca groups, one of the nitrogen atoms of the dmphen molecule (1 and 2) and either one nitrile-nitrogen from a terminal dca ligand (1) or a nitrate-oxygen atom (2) build the equatorial plane whereas the second nitrogen atom of the heterocyclic dmphen fills the axial position (1 and 2). The copper-copper separations through double (1) and single (2) end-to-end dca bridges are 7.1337(7) (1) and 7.6617(7) (2). Compound 3 is a mononuclear copper(II) complex whose structure contains two neutral and crystallographically independent [Cu(4,4^′-dmbpy)(H₂O)(dca)₂] molecules which are packed in two different layer arrangements running parallel to the bc-plane and alternating along the a-axis. The copper atoms in both molecules have slightly distorted square pyramidal surroundings with the two nitrogen atoms of the 4,4^′-dmbpy ligand and two dca nitrile-nitrogen atoms in the basal plane and a water oxygen in the apical position. A semi co-ordinated dca nitrile-nitrogen from a neighbour unit [2.952(6) Å for Cu(2)-N] is in trans position to the apical water molecule in one of the two molecules, this feature representing part of the difference in supramolecular connections in the alternating layers referred to above. Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K reveal the occurrence of weak antiferromagnetic interactions through double [J=−3.3 cm⁻¹ (1), ] and single [J=−0.57 cm⁻¹ (2), ] dca bridges and across intermolecular contacts [θ=−0.07 K (3)].     

Two-dimensional oxides constructed from octamolybdate clusters and M/tetrapyridylpyrazine subunits (M = Co, Ni: n = 2; M = Cu: n = 1)

The hydrothermal reactions of MoO₃, tetra-2-pyridylpyrazine (tpyprz) and M(CH₃CO₂)₂ · 2H₂O (M = Co, Ni) yielded the two-dimensional oxides [M₂(tpyprz)(H₂O)₂Mo₈O₂₆] · xH₂O [M = Co, x = 1.8 (1); M = Ni, x = 0.6 (2)]. However, the reaction of (NH₄)₆Mo₇O₂₄ · 4H₂O, tpyprz and Cu(CH₃CO₂)₂ · H₂O produced [{Cu₂(tpyprz)}₂Mo₈O₂₆] · 2H₂O (3 · 2H₂O). The isomorphous structures of 1 and 2 are constructed from clusters linked through {M₂(tpyprz)(H₂O)₂}⁴⁺ subunits into two-dimensional networks. While the structure of 3 is also two-dimensional, the molybdate building block is present as the δ-isomer and the secondary-metal/ligand component consists of a one-dimensional chain. The structure of 3 is compared to that of the previously reported three-dimensional material [{Cu₂(tpyprz)}₂Mo₈O₂₆] · 7H₂O which contains clusters and structurally distinct chains.