Effect of outer sphere anions on the structure and color of nitrosylpentaamminechromium complex

Three kinds of crystalline compounds containing the nitrosylpentaamminechromium complexes [Cr(NO)(NH₃)₅]²⁺(A) were obtained: chloride ACl₂ (red-orange), chloride perchlorate ACl(ClO₄) (brown), and perchlorate A(ClO₄)₂ (green). The cause of the color change of the complex A with the change of outer sphere anions was sought using X-ray structural data of ACl₂, ACl(ClO₄), and A(ClO₄)₂. Crystal data: ACl₂, orthorhombic, space group Cmcm, a=10.0236 (9) Å, b=9.098 (3) Å, c=10.357(1) Å, V=944.5 (5) ų, Z=4; ACl(ClO₄), tetragonal, space group P4/nmm, a=7.6986 (8) Å, c=9.9566(8) Å, V=590.1 (1) Å^3,Z=2; A(ClO₄)₂, orthorhombic, space group Pnma, a=15.760 (2) Å, b=11.480(2) Å, c=7.920 (2) Å, V=1432.9 (4) ų, Z=4. The complex cation in ACl₂ has a distorted octahedral structure with a linear CrNO moiety. The short CrN (nitrosyl) distance of 1.692 (7) Å indicates the presence of multiple bonding between the chromium atom and the nitrogen atom in the nitrosyl group. The interatomic distances and angles within the complex cations hardly change with the change of the counter anions, while the distances between the complex cations in each crystal increase in the order ACl₂<ACl(ClO₄)<A(ClO₄)₂. The bulky perchlorate anions seems to separate the complex cations, while smaller chloride anions are not large enough to separate them. The distance (3.213(5) Å) between O(NO) and N(NH₃ in the adjacent complex cation) is rather short in the crystal of ACl₂, and there are six hydrogen bonds, where the NO group is surrounded by four NH₃ ligands. The distance (4.002(5) Å) between O(NO) and N(NH₃) is much longer in the crystal of A(ClO₄)₂, indicating the presence of no hydrogen bonding. In the crystal of ACl(ClO₄) the distance (3.452(4) Å) between O(NO) and N(NH₃) is in between those of ACl₂ and A(ClO₄)₂. The presence of hydrogen bonding between O(NO) and N(NH₃ in the adjacent complex cation) seems to cause the color change with the change of outer sphere anions.     

Hydrogen-bond assisted stabilization of the less favored conformation of a tridentate Schiff base ligand in dinuclear nickel(II) complex: An experimental and theoretical study

The Schiff base ligand, HL (2-[1-(3-methylamino-propylimino)-ethyl]-phenol), the 1:1 condensation product of 2-hydroxy acetophenone and N-methyl-1,3-diaminopropane, has been synthesized and characterized by X-ray crystallography as the perchlorate salt [H₂L]ClO₄ (1). The structure consists of discrete [H₂L]⁺ cations and perchlorate anions. Two dinuclear Ni^II complexes, [Ni₂L₂(NO₂)₂] (2), [Ni₂L₂(NO₃)₂] (3) have been synthesized using this ligand and characterized by single crystal X-ray analyses. Complexes 2 and 3 are centrosymmetric dimers in which the Ni^II ions are in distorted fac- and mer-octahedral environments, respectively, bridged by two μ₂-phenolate ions of deprotonated ligand, L. The plane of the phenyl rings and the Ni₂O₂ basal plane are nearly coplanar in 2 but almost perpendicular in 3. We have studied and explained this different behavior using high level DFT calculations (RI-BP86/def2-TZVP level of theory). The conformation observed in 3, which is energetically less favorable, is stabilized via intermolecular non-covalent interactions. Under the excitation of ultraviolet light, characteristic fluorescence of compound 1 was observed; by comparison fluorescence intensity decreases in case of compound 3 and completely quenched in compound 2.     

Synthesis and structural characterizations of four polyoxometalate compounds consisting of transition metals or alkaline cations as the bridging units

Four new polyoxometalate compounds, namely [Cu₂(pyrazine)₄][Cu(pyrazine)₂][PMo₁₂O₄₀] · 2H₂O (1), {[K(H₂O)₂]₄H₈PW₁₂O₄₄}F · 8H₂O (2), H₉[K₂KMo₃₆O₁₁₂(H₂O)₃₄] · 35H₂O (3), and H₃Na₃[V₁₀O₂₈] · 15H₂O (4), were prepared and characterized by single crystal X-ray diffraction, elemental analysis and IR spectroscopy. Single crystal X-ray diffraction analysis results reveal that, in compound 1, Keggin anion of [PMoO₁₂O₄₀]³⁻ is enchased in the bowl-like Cu(I)-pyrazine intervals via weak interactions between terminal oxygen atoms and cations of Cu(I). For compound 2, a three-dimensional architecture with pores of 7.70 × 7.70 Å is constructed from the anions of [PW₁₂O₄₄]¹¹⁻ cross-linked via corner-sharing alkali cations of K⁺. The [Mo₃₆O₁₁₂(H₂O)₁₆]¹²⁻ units of compound 3 are linked to form one wave-like chain via cations of K⁺. Whereas, in compound 4, anions of [V₁₀O₂₈]³⁻ are linked via NaO₆ octahedra to form two-dimensional layer structure. On the basis of this two-dimensional layer, a three-dimensional architecture is further formed via hydrogen bonds involving edge-shared NaO₆ double octahedron.     

Synthesis, structure and solution chemistry of dioxidovanadium(V) complexes with a family of hydrazone ligands. Evidence of formation of centrosymmetric dimers via H-bonds in the solid state

[V^IVO(acac)₂] reacts with the methanol solution of tridentate ONO donor hydrazone ligands (H₂L^1-4, general abbreviation H₂L; are derived from the condensation of benzoyl hydrazine with 2-hydroxyacetophenone and its 5-substituted derivatives) in presence of neutral monodentate alkyl amine bases having stronger basicity than pyridine e.g., ethylamine, diethylamine, triethylamine and piperidine (general abbreviation B) to produce BH⁺[VO₂L]⁻ (1-16) complexes. Five of these sixteen complexes are structurally characterized revealing that the vanadium is present in the anionic part of the molecule, [VO₂L]⁻ in a distorted square pyramidal environment. The complexes 5, 6, 15 and 16 containing two H-atoms associated with the amine-N atom in their cationic part (e.g., diethylammonium and piperidinium ion) are involved in H-bonding with a neighboring molecule resulting in the formation of centrosymmetric dimers while the complex 12 (containing only one hydrogen atom in the cationic part) exhibits normal H-bonding. The nature of the H-bonds in each of the four centrosymmetric dimeric complexes is different. These complexes have potential catalytic activity in the aerial oxidation of l-ascorbic acid and are converted into the [VO(L)(hq)] complexes containing VO³⁺ motif on reaction with equimolar amount of 8-hydroxyquinoline (Hhq) in methanol.     

New supramolecular complexes generated from Mn, Fe, Co, Zn, Fe with a bent dipyridyl ligand: Metal- and anion-directed assembly

Assemblies of an angular dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) with a series of metal perchlorate afford five new supramolecular complexes with the general formula of [M(4-bpo)₂(H₂O)₄] · (4-bpo)₂ · (anion) · (solvent), in which M = Mn^II for 1, Fe^II for 2, Co^II for 3, Zn^II for 4, and Fe^III for 5. Although similar molecular structures and compositions are found for these mononuclear complexes, they display two types of supramolecular lattices. Complexes 1, 4 and 5 similarly crystallize in space group P2/n or P2/c. The complex cations, free 4-bpo and lattice water are linked to generate 2D layered frameworks with the aid of hydrogen bonding, and the counter anions are located within and between (also methanol in 5) these 2D arrays. However, complexes 2 and 3 are isostructural in space group . Two types of alternate 2D layers consisting of complex cations and free 4-bpo components, respectively, are observed with the anions and lattice water locating between them. These motifs are interlinked by complicated hydrogen-bonding to form a 3D intercalated network. Moreover, when Co(NO₃)₂ is used instead of Co(ClO₄)₂ in the assembly of 3, a 1D polymeric chain complex {[Co(4-bpo)(H₂O)₂(NO₃)₂](H₂O)₃}_n (6) is generated. These results indicate that the choice of metal ion and anion exerts a significant influence on governing the target complexes. A comparison of the structural features for all metal perchlorate complexes with 4-bpo is also briefly discussed.     

Two new supermolecular structures of organic-inorganic hybrid compounds: [Zn(phen)(SO4)(H2O)2]n and [Cu(phen)(H2O)2] · SO4 (phen = 1,10-phenanthroline)

Two new organic-inorganic hybrid compounds [Zn(phen)(SO₄)(H₂O)₂]_n (1) and [Cu(phen)(H₂O)₂] · SO₄ (2) have been prepared by conventional aqueous solution synthesis and characterized by single-crystal X-ray diffraction, IR spectroscopy, thermal gravimetric analysis (TGA) and fluorescent spectroscopy. In compound 1, the sulfate group adopts bidentate mode to coordinate with two Zn(II) ions to form one-dimensional polymer. The one-dimensional polymers are further linked together via the intermolecular hydrogen-bonding and π-π stacking interactions to form a 3D supramolecular framework. Compound 2 is build up of discrete [Cu(phen)(H₂O]²⁺ cations and SO₄²⁻ anions to form a three-dimensional framework via hydrogen-bonding and π-π stacking interactions. Furthermore, the luminescent properties of both 1 and 2 were studied. The complexes 1 and 2 excited at 280 nm wavelength produced characteristic luminescence features, arising maybe due to the π-π transitions.     

Effect of flexibility of organic dicarboxylates anions on the four 3D metal-organic frameworks constructed from flexible benzimidazolyl-based ligand

Four new polymeric frameworks, [Co(bbbi)(L1)] (1), [Cu(bbbi)(L1)] (2), [Co(bbbi)(L2)] (3) and [Ni(bbbi)(L2)] (4), (bbbi = 1,1-(1,4-butanediyl)bis-1H-benzimidazole, H₂L1 = 5-nitroisophthalic acid and H₂L2 = itaconic acid) have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Complexes 1 and 2 are isomorphous, and they can be described as CsCl-type net utilizing bimetal cores as eight-connected nodes, the bridging bbbi ligands and L1 serve as spacers to yield a unique eight-connected net with 4²⁴6⁴ topology. Complexes 3 and 4 are isomorphous. It is interesting that 3D frameworks containing meso-helical chains (left- and right helical chains) have been observed in 3 and 4, in which meso-helical chains are alternately linked by bbbi ligands coordinating to Co1(Ni1) cations with the zigzag shaped conformation to generate a 3D binodal (4,4)-connected net with {5³·6·8²}{5²·6⁴} topology structure. The bbbi ligands adopt three conformations, namely, the completely “M” shaped conformation in 1 and 2, the zigzag shaped conformation and “Ω” shaped conformation in 3 and 4. The influence of carboxylate anions with different flexibility on the construction of different network topology in the self-assembly process has been discussed. Moreover, the thermal stabilities and the voltammetric behavior of complexes 1-4 have been reported.     

The role of non-classical supramolecular interactions in the structures of 2-amino-4,6-dimethylpyridinium tetrahalocuprate (II) salts

The compounds [2-amino-4,6-dimethylpyridinium]₂CuCl₄ (1) and [2-amino-4,6-dimethylpyridinium]₂CuBr₄ (2) were prepared from acidic ethanolic media containing CuX₂ and [2-amino-4,6-dimethylpyridine] in the molar ratio 1:1. The compounds were characterized by IR and single-crystal X-ray diffraction and found to be isomorphous in the space group with V = 991.2(10) Å³ for (1) and 1059.26(12) Å³ for (2) . There is no significant difference in the non-classical N-H?X hydrogen bonding between (1) and (2). The anions show essentially the same extent of distortion from tetrahedral geometry with max./min. values for the X-Cu-X bond angles of 139.72(6)°/96.78(6)° for (1) and 139.43(4)°/96.64(3)° for (2). Each [CuX₄]²⁻ anion is hydrogen bonded nonsymmetrically to four cations. In this manner, ladder chains are formed that run along the b-axis, with planar cations falling parallel to the (2, 0, 1) plane. Weaker π-π interactions exist between cations from different chains with centroid to centroid distance of 4.07 Å in (1) and a long 4.594 Å in (2). The X-π electrostatic interactions are surprisingly stronger in (2) than in (1) with a Br to centroid of pyridinic ring distance of 3.890 Å compared with 3.996 Å for the chloride analogue.     

Crystal structures and catalytic activities of Zn(II) compounds containing btp ligands

The structures of new compounds containing Zn(II) ions and btp (2,6-bis(N′-1,2,4-triazolyl)pyridine) ligands have been determined. With coordinating chloride and bromide anions, Zn(II) produces chains 2 and 3 containing C-H?X(Cl or Br) weak interactions to build crystal structures and they are face-to-face aligned. With non-coordinating anions, Zn(II) produces monomeric compounds 4 and 5 containing H-bonds between anions and water ligands and face-to-face π-π interactions to build crystal structures. The previously reported polymeric compound 1 containing [Zn(NO₃)(H₂O)₂(btp)₂]⁺ units bridged by btp ligands was found to carry out the catalytic transesterification of a range of esters with methanol at room temperature under mild conditions, whereas it did not catalyze the ring opening of epoxide (easier reaction) with methanol. These results indicate that the polymeric compound 1 shows selective reactivity. In addition, the catalyst 1 has shown even better catalytic activity than the corresponding Zn(NO₃)₂ salt.     

Solvatothermal chemistry of organically-templated vanadium fluorides and oxyfluorides

The solvatothermal reactions of V₂O₅, the appropriate organoamine and HF in the temperature range 100-180 °C yielded a series of vanadium fluorides and oxyfluorides. The compounds [NH₄][H₃N(CH₂)₂NH₃][VF₆] (1) and [H₃N(CH₂)₂NH₃][VF₅(H₂O)] (2) contain mononuclear V(III) anions, while [H₃N(CH₂)₂NH₂(CH₂)₂NH₃]₂ [VF₅(H₂O)]₂[VOF₄(H₂O)] (3) exhibits both V(IV) and V(III) mononuclear anions. Both compound 4, [H₃NCH₂(C₆H₄)CH₂NH₃][VOF₄]·H₂O (4·H₂O) and compound 5, [HN(C₂H₄)₃NH][V₂O₂F₆ (H₂O)₂] (5) contain binuclear anions constructed from edge-sharing V(IV) octahedra. In contrast, [H₃N(CH₂)₂NH₂(CH₂)₂NH₃]₂[V₄O₄F₁₄(H₂O)₂], (6) exhibits a tetranuclear unit of edge- and corner-sharing V(IV) octahedra. Compound 7, [H₃N(CH₂)₂NH₂][VF₅], contains chains of corner-sharing {V^IVF₆} octahedra, while [H₂N(C₂H₄)₂NH₂]₃[V₄F₁₇O]·1.5H₂O (8·1.5H₂O) is two-dimensional with a layer of V(III) and V(IV) octahedra in an edge- and corner-sharing arrangement. In the case of [H₃N(CH₂)₂NH₃][V₂O₆] (9), there was no fluoride incorporation, and the anion is a one-dimensional chain of corner-sharing V(V) tetrahedra.     

Mn(II) coordination architectures with mixed ligands of 3-(2-pyridyl)pyrazole and carboxylic acids bearing different secondary coordination donors and pendant skeletons

In our efforts to investigate the factors that affect the formation of coordination architectures, such as secondary coordination donors and pendant skeletons of the carboxylic acid ligands, as well as H-bonding and other weak interactions, two kinds of ligands: (a) 3-(2-pyridyl)pyrazole (L¹) with a non-coordinated N atom as a H-bonding donor, a 2,2′-bipyridyl-like chelating ligand, and (b) four carboxylic ligands with different secondary coordination donors and/or pendant skeletons, 1,4-benzenedicarboxylic acid (H₂L²), 4-sulfobenzoic acid (H₂L³), quinoline-4-carboxylic acid (HL⁴) and fumaric acid (H₂L⁵), have been selected to react with Mn(II) salts, and five new complexes, [Mn(L¹)₂(SO₄)]₂ (1), [Mn(L¹)₂(L²)]_∞ (2), [Mn(L¹)(HL³)₂]_∞ (3), Mn(L¹)₂(L⁴)₂ (4), and [Mn(L¹)₂(L⁵)]_∞ (5), have been obtained and structurally characterized. The structural differences of 1-5 can be attributed to the introduction of the different carboxylic acid ligands (H₂L², H₂L³, HL⁴, and H₂L⁵) with different secondary coordination donors and pendant skeletons, respectively. This result also reveals that the typical H-bonding (i.e. N-H?O and O-H?O) and some other intra- or inter-molecular weak interactions, such as C-H?O weak H-bonding and π?π interactions, often play important roles in the formation of supramolecular aggregates, especially in the aspect of linking the multi-nuclear discrete subunits or low-dimensional entities into high-dimensional supramolecular networks.     

Synthesis and structures of three d metal coordination polymers constructed from flexible polycarboxylate and 1,10-phenanthroline ligands

Three novel d¹⁰ metal coordination polymers, {[Cd(H₂odpa)(phen)₂]·H₂O}_n (1), [Cd₂(odpa)(phen)(H₂O)₂]_n (2), {[Zn₄(odpa)₂(phen)₂(H₂O)₂]·H₂O}_n (3), (H₄odpa = 4,4′-oxydiphthalic acid, phen = 1,10-phenanthroline) were obtained with different metal/ligand ratios through hydrothermal method and characterized. Compound 1 forms a one dimensional zigzag chain, in which two phen ligands chelate to one cadmium atom. Compound 2 shows a three dimensional network structure comprised of new tetranuclear cadmium clusters as the nodes and (odpa)⁴⁻ anions as the linkers, exhibits an unusual topological structure. Compound 3 is an unprecedented three dimensional polymer based on octanuclear zinc clusters cross-linked by (odpa)⁴⁻ anions. In 1-3, central Cd^II/Zn^II ions and (odpa)⁴⁻ ligand display completely different coordination modes and conformations. In addition, the thermal stabilities and photoluminescence properties of 1-3 were also studied.     

Reduction of structural dimensionality through incorporation of auxiliary ligands in lanthanide tetracyanoplatinates

The synthesis of a series of lanthanide tetracyanoplatinates containing the auxiliary ligands 1,10′-phenanthroline (phen) or 2,2′-bipyridine (bpy) have been carried out by reaction of Ln³⁺ nitrate salts with phen or bpy and potassium tetracyanoplatinate in solvent systems containing dimethylsulfoxide and dimethylformamide. The use of these solvents has lead to the isolation of [{Ln(DMSO)₂(C₁₂H₈N₂)(H₂O)₃}₂Pt(CN)₄](Pt(CN)₄)₂·2C₁₂H₈N₂·4H₂O (Ln = Eu (Eu-1), Tb (Tb-1), Yb(Yb-1)), [Ln(DMF)₃(C₁₂H₈N₂)(H₂O)₂NO₃]Pt(CN)₄ (Ln = La (La-2), Eu (Eu-2), Tb (Tb-2)), and [Ln(DMF)₃(C₁₀H₈N₂)(H₂O)₂NO₃]Pt(CN)₄ (Ln = La (La-3), Sm (Sm-3), Eu (Eu-3), Tb (Tb-3)) in the form of single crystals. Single-crystal X-ray diffraction has been used to investigate their structural features. The use of DMSO versus DMF as the solvent results in markedly different structural features. Eu-1 contains [{Eu(DMSO)₂(C₁₂H₈N₂)(H₂O)₃}₂Pt(CN)₄]²⁺ complex cations where the two Eu³⁺ centers are linked by a trans-bridging Pt(CN)₄²⁻ anion to form a dimeric lanthanide complex cation. An additional uncoordinated Pt(CN)₄²⁻ anion balances charge. Eu-2 and Eu-3 consist of zero-dimensional salts with [Eu(DMF)₃(C₁₂H₈N₂)(H₂O)₂(NO₃)]²⁺ or [Eu(DMF)₃(C₁₀H₈N₂)(H₂O)₂(NO₃)]²⁺ complex cations, respectively, and only non-coordinated Pt(CN)₄²⁻ anions. Photoluminescence measurements illustrate that the Eu³⁺ and Tb³⁺ compounds for all three structure types display enhanced emission due to intramolecular energy transfer from the coordinated cyclic amines.     

Different coordination modes of Hdipic and dipic ligands to nickel(II) ions in a same environment (dipic = 2,6-pyridinedicarboxylate, dipicolinate)

Two new nickel(II) complexes of the composition [Ni(cyclam)(Hdipic)₂] · 2H₂O (1) and [Ni(cyclam)(H₂O)₂][Ni(dipic)₂] · 2.5H₂O (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) have been prepared and structurally characterized by a combination of analytical, spectroscopic, thermogravimetric, and crystallographic methods. The structure of 1 shows that the central nickel(II) ion is coordinated axially by two monodentate Hdipic ligands. The discrete neutral complex 1 further extends its structure by hydrogen bonding interactions to form a one-dimensional supramolecule. The structure of 2 consists of two independent nickel(II) centers. Water molecules instead of dipic ligands prefer to coordinate to the Ni1 ion forming a divalent cation [Ni(cyclam)(H₂O)₂]²⁺. Two dipic ligands coordinate to the second Ni2 ion forming a divalent anion [Ni(dipic)₂]²⁻. The divalent cations and anions are charge-balanced, resulting in a molecular salt. The divalent cations and anions are interconnected by multiple types of hydrogen bonding interactions.     

Crystal structures and catalytic activities of Zn(II) compounds containing 1,3-bis(4-pyridyl)propane

The structures of new compounds containing Zn(II) ions and bpp (1,3-bis(4-pyridyl)propane) ligands have been determined. The coordinating halides (Br⁻ or Cl⁻) produce one-dimensional compounds 6 and 7, and intra- and inter-chain CH?X (X = Br or I) interactions play roles for building crystal structures with the flexible bpp ligands. The non-coordinating anions do not produce hydroxyl bridged zinc cations or polymeric compounds, and produce only a monomeric complex 4 containing four bpp ligands and two water ligands. Previously reported polymeric compounds 1 and 2 containing hydroxyl-bridged zinc cations [Zn₂OH] were found to carry out the catalytic transesterification of a range of esters with methanol at room temperature under the mild conditions, whereas the rest of compounds did not catalyze the transesterification reactions at all. In addition, the catalysts 1 and 2 have shown even better catalytic activity than zinc salts Zn(NO₃)₂ and Zn(OTf)₂.     

Syntheses, crystal structures, and magnetic properties of Ni(mnt)2-based molecular solids containing substituted isoquinolinium

Two novel ion-pair complexes, [RBzIQl]⁺[Ni(mnt)₂]⁻ (mnt²⁻ = maleonitriledithiolate, [RBzIQl]⁺ = 4-R-benzylisoquinolinium; R = H (1), Cl (2)) have been characterized structurally and magnetically. The anions and [BzIQl]⁺ cations of 1 form 1D column of alternating between cations and anions via π?π stacking interaction between Ni(mnt)₂ plane and isoquinoline ring, and the Ni(mnt)₂ anions between adjacent columns exist C?N, C?N, and N?N interaction. The anions and cations of 2 stack into well-segregated columns in the solid state; and the Ni(III) ions form a 1D zigzag chain in a Ni(mnt)₂ column through intermolecular Ni?S, S?S, Ni?Ni or π?π interactions. The chain is uniform in 2 with the Ni?Ni distances of 3.784 Å. Magnetic susceptibility measurements for these complexes in the temperature range 1.8-300 K show that 1 exhibits antiferromagnetic coupling behavior, and 2 exhibits unusual magnetic phase transitions around 45 K. The overall magnetic behavior for 2 indicates the presence of antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT).     

Anion-directed assembly of metal-organic coordination complexes from 1,3-imidazolidine-2-thione ligand and silver salts

Five novel silver (Ι) complexes with 1,3-imidazolidine-2-thione ligand formulated as [Ag₂(η¹-SC₃H₆N₂)₆]SO₄ (1), [Ag₂(μ₂-SC₃H₆N₂)₂(η¹-SC₃H₆N₂)₄](NO₃)₂ (2), [Ag(μ₂-SC₃H₆N₂)Br]_n (3), [Ag₂(μ₂-SC₃H₆N₂)₃(CH₃COO)₂]_n (4), [Ag(μ₂-SC₃H₆N₂)Cl]_n (5) have been synthesized under similar conditions except for different anions and solvents. They are structurally characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. Complex 1 is a binuclear complex, with SO₄²⁻ anions as the counteranions. Complex 2 is a molecular binuclear silver cluster, with NO₃⁻ anions as the counteranions. Complex 3 shows a novel 2D lamella structure constructed by the S atom of 1,3-imidazolidine-2-thione ligand and Br⁻ anions, and exhibits 12-membered metallacyclic rings in its structure. Complex 4 is a novel 2D layered polymer with a graphite-like array of silver (I) ions, with CH₃COO⁻ anion coordinated to silver(I) ions by O atom. Complex 5 shows a 3D diamond-like network structure constructed by the sulfur atom of 1,3-imidazolidine-2-thione ligand and Cl⁻ anions.     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

Synthesis and molecular structure of trinuclear mixed-metal cluster cations containing arene and hydrido ligands

The mixed-metal trinuclear cluster cations [H₃Ru₂(C₆Me₆)₂Os(C₆H₆)(O)]⁺ (1), [H₃Ru₂(1,2,4,5-C₆H₂Me₄)₂Os(p-MeC₆H₄ⁱPr)(O)]⁺ (2) and [H₃Ru₂(1,2,4,5-C₆H₂Me₄)₂Os(C₆H₆)(O)]⁺ (3) have been synthesised from the corresponding dinuclear precursors [H₃Ru₂(arene)₂]⁺ and the corresponding mononuclear complexes [Os(arene)(H₂O)₃]²⁺, isolated and characterised as the tetrafluoroborate and hexafluorophosphate salts. The cations 1, 2 and 3 are heteronuclear analogues of the cluster cation [H₃Ru₃(C₆H₆)(C₆Me₆)₂(O)]⁺ that possesses a homonuclear metallic core. The single-crystal X-ray structure analyses of [1][BF₄], [2][PF₆] and [3][PF₆] reveal an equiangular metal triangle despite the presence of an osmium atom in the metallic core.     

Oxime-functionalized diazamesocyclic derivates and their metal complexes: Effect of the ligand backbones and anions on the generation of novel monomeric and mono-μ-Cl dimeric Cu complexes

Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H₂L¹) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H₂L²), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with Cu^II and Ni^II salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H₂L¹ with Cu(ClO₄)₂ and Ni(ClO₄)₂ afford a penta-coordinated mononuclear complex [Cu(H₂L¹)Cl] · ClO₄ (1) and a four-coordinated monomeric [Ni(HL¹)] · ClO₄ (2), in which the ligand is monodeprotonated. The ligand H₂L² also forms a quite similar mononuclear [Ni(HL²)] · ClO₄ complex with Ni(ClO₄)₂, according to our previous work. However, reactions of different Cu^II salts [Cu(ClO₄)₂, CuCl₂ and Cu(NO₃)₂ for 3, and CuSO₄ for 4] with H₂L² in the presence of NaClO₄ yield two unusual mono-μ-Cl dinuclear Cu^II complexes [Cu₂(HL²)₂Cl] · (ClO₄) (3), and [Cu₂(H₂L²)(HL²)Cl] · (ClO₄)₂ · (H₂O)(4). These results indicate that the resultant Cu^II complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions.