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.     

In situ alkylation of 4,4′-bipyridine in hydrothermal synthesis of one-dimensional copper(I) bromide compounds

Hydrothermal reaction of CuBr₂, 4,4′-bipyridine and ethanol/methanol generated two copper (I) bromide complexes with in situ alkylated 4,4′-bipyridium, namely [C₁₄H₁₈N₂][Cu₅Br₇] (1) and [C₁₂H₁₄N₂][Cu₄Br₆] (2). The structure of 1 consists of chains and N,N′-diethyl-4,4′-bipyridinium. The underlying structural motif in of 1 is the Cu₅Br capped square pyramid, which is different from the Cu₅Br₂ pentagonal bipyramidal structural motif in various documented anions. The in 1 contains untypical μ₅-bromide, with which five copper atoms forms a capped square pyramid rather than a pentagonal pyramid as predicted by Subramanian and Hoffmann. Compound 2 is isostructural with [C₁₂H₁₄N₂][Cu₄Cl₆] reported by Willett, and consists of chains and N,N′-dimethyl-4,4′-bipyridinium. The chain is composed of alternating Cu₆Br₆ and Cu₂Br₆ units.     

Structural characterization of several cadmium halides with N-donor ligands

Five cadmium halides with N-donor ligands were synthesized under the hydrothermal conditions and characterized by X-ray single-crystal diffraction. The isostructural [CdX₂(2,2′-bpy)] (X = I 1, Br 2, bpy = bipyridine) (1) possess 3-D supramolecular network structures based on 1-D zigzag-type CdX₂ chains extended by bpy molecules via non-covalent C-H?X hydrogen-bonded interactions. The 3-D porous [CdBr₂(pip)] (pip = piperazine) (3) is formed through a linkage of 1-D zigzag-type CdBr₂ chains by pip bridges. The heteronuclear dimetal-iodo cluster [Cu(phen)₂CdI₄] (phen = phenanthroline) (4) consists of a trigonal bipyramidal Cu(II) center and a tetrahedral Cd(II) center linked by a μ₂-I bridge. The ionic [Co(dien)₂][CdI₄] (dien = diethylenetriamine) (5) comprises an octahedral cation and a tetrahedral anion.     

Square-planar and trigonal prismatic silver(I) in bipyrimidine and oxalate bridged tetranuclear complexes and one-dimensional compounds: Synthesis and crystal structures

The reaction of [Ag₄(hfac)₄(THF)₂] (hfac⁻ = 1,1,1,5,5,5-hexafluoroacetylacetonate, THF = tetrahydrofurrane) with 2,2′-bipyrimidine (bpm) leads to single crystals. They crystallise in the triclinic system, space group . Their structure consists of [Ag₄(hfac)₄(μ₂-bpm)₃] tetranuclear complexes. In this complex, Ag(I) ions adopt distorted square planar and trigonal prismatic geometries. When [Ag₄(hfac)₄(THF)₂] is replaced by monohydrated silver(I) perchlorate, a one-dimensional (1D) compound with a formula of [[Ag(μ₂-bpm)]⁺]_n, is obtained as single crystals. They crystallise in the monoclinic system, space group P2₁/c. Their structure consists of [[Ag(μ₂-bpm)]⁺]_n chains separated by non-coordinated perchlorate ions. In the chains, the Ag(I) centres adopt a square planar geometry. Finally, starting from [[Ag(μ₂-bpm)]⁺]_n, and sodium oxalate , another 1D compound with a formula of [Ag(μ₂-bpm)(μ₂-ox)]_n, 4nH₂O is obtained as single crystals. They crystallise in the triclinic system, space group . In these chains, bipyrimidine and oxalate are alternate. They generate a square planar geometry around the Ag(I) cations.     

3D coordination polymer of copper (II)-potassium (I): Crystal structure and thermal decomposition kinetics

A new heterometallacrown coordination polymer [K₂Cu(NPA)₂(H₂O)₄]_n (where H₂NPA = 3-nitro-phthalic acid) has been synthesized and it’s crystal structure has been elucidated. In the complex, the o-phthalate group coordinates to metal atoms behaving as both tetradentate and heptadentate coordination, the modes of which have been found for the first time. The thermal behaviors of this complex and the thermal decomposition kinetics have been studied. Kinetic analysis shows that the decomposition of title complex in the main range acts as two separate transitions with the first one being a double-step following reaction, , and the second being a three-step following reaction of t:f,f, . The kinetic parameters of these processes were also obtained.     

Double salts of copper(I) chloride incorporated hydroxylpyrimidine and tetrazole ligands

Hydrothermal reaction of copper(II) chloride with 2-hydroxypyrimidine generated double salt of [Cu₂Cl(μ₄-pymo)] (1) (Hpymo = hydroxylpyrimidine) while hydrothermal treatment of CuCl₂, NaN₃ and acetonitrile resulted in double salt of [Cu₂(mtta)Cl] (2) (Hmtta = 5-methyltetrazole) in which in situ [2 + 3] cycloaddition reactions of acetonitrile with azide formed mtta ligand. X-ray single crystal structural analyses revealed that 1 shows a two-dimensional layer formed by fusion of one-dimensional structural motifs. The two-dimensional layers in 1 are held together by C-H?Cl hydrogen bonds to form three-dimensional supramolecular array. Compound 2 has a three-dimensional framework constructed from ribbons and [Cu₈Cl₄]⁴⁺ units. Uncommon coordination modes of μ₄-1,2κO:3κN:4κN′ pymo and μ₄-Cl (Cl at the apex of a Cu₄Cl square pyramid) in 1 and μ₄-η¹:η¹:η¹:η¹ mtta in 2 were also observed. The short Cu(I)?Cu(I) distances were found in 1 and 2, indicating the existence of Cu(I)?Cu(I) interactions.     

Argentophilic interaction and anionic control of supramolecular structures in simple silver pyridine complexes

The synthesis and characterization of three simple 1:2 silver(I) pyridine adducts of different counter-anions, [Ag(py)₂]⁺ · X⁻ (X = ClO₄, 1; BF₄, 2; PF₆, 3), are reported. The structural studies for 1-3 reveal the presence of strong ligand-unsupported argentophilic interactions between [Ag(py)₂]⁺ ions, forming pairs of . The Ag?Ag contact distances are 2.96-3.00 Å. In 1 and 2, pairs of are further linked into 1-D infinite chains by a combined set of multiple Ag?Ag close contacts (3.34-3.37 Å), offset ‘head to head’ π-π stacking, and anion bridging interactions. Such combined set of interactions is anion-dependant with 1 and 2 containing anions of tetrahedral geometry and , affording essentially the same supramolecular architecture. Metal-anion interactions are crucial in organizing the 1-D chains into 3-D networks. The ES-MS studies of 1 and 2 provide positive evidence for the aggregation of silver(I) ions in solution. In contrast, for 3 with the counter-anion of octahedral , pairs of are organized into a 3-D network via a combined set of Ag?F contacts, C(H)?F hydrogen bonds, and ‘head to tail’ π-π stacking interactions. No extended 1-D polymeric chains of silver ions are present in 3.     

Platinum(II) and copper(I) 1-(2-diphenylphosphino-1-naphthyl) isoquinoline complexes: Synthesis and phosphorescence at ambient conditions

The compounds Pt(quinap)(CN)₂, and [Cu(quinap)I]₂ with quinap = 1-(2-diphenylphosphino-1-naphthyl)isoquinoline were synthesized. Quinap is a bidentate ligand which contains a isoquinoline and an arylphosphine group with CT acceptor properties. Accordingly, the Pt(II) and Cu(I) quinap complexes are characterized by a phosphorescence originating from the lowest-energy MLCT triplets with some IL admixture.     

Synthesis and single crystal structural investigations on quaternary salts of tellurated alkylamine derivatives

Tellurated alkylamine derivatives , , and have been synthesized by reacting appropriate organic halides with the nucleophile 4-CH₃OC₆H₄Te⁻ or Te²⁻ generated in situ by borohydride reduction of (4-CH₃OC₆H₄Te)₂ or Te powder followed by reaction with HCl of appropriate concentration. The zwitterionic species was generated when single crystals of 2 were grown in methanol at 0 °C. Complexes 1-4 exhibit characteristic ¹H NMR spectra. The single crystal structures of 1-4 and 2a have been determined. In the crystals of 1, C-H?π distances have been found to be 3.31(7)-3.59(5) Å. In both 2 and 2a, weak Te?Cl interactions (3.54(2) -3.62(2) Å) are observed. The C-H?π distance in the crystal of 2 is 3.19(0) Å. In 2a and 3, water hydrogen bonds connect the water molecules with the end groups from different molecules. In the case of 3, Te?Cl weak interactions involving the Cl⁻ ions connect together two such chains. The geometry of Te in 1 is V shaped. In 2 and 3 it is pseudo trigonal bipyramidal, and in 2a, it is square pyramidal. However, in the latter case it becomes distorted octahedral due to weak Te?Cl secondary interactions. The geometry about Te in 4 is distorted octahedral due to weak Te?Cl interactions involving Cl⁻ ions. However, there are no intermolecular Te?Cl interactions.     

Oligomerization of the Cu(II) and Ni(II) tetraazaannulene complexes: A pulse radiolysis study of the associated reaction mechanism

The oligomerization of [Cu^II(H_x(tmdnTAA))]^x+ (x = 0, 1, 2 and (tmdnTAA))²⁻ is 2,4,9,11-tetramethyl-dinaphto[14]-2,4,6,9,11,13-hexaeneN₄) was initiated in homogeneous solution via the reaction of this Cu(II) complex with pulse radiolytically generated radicals. The reaction produces Cu(III) intermediates which are rapidly converted to Cu(II) ligand-radical species. In contrast to the mechanism proposed for the electrochemical oligomerization, where the local concentration of radicals is probably high, the reaction kinetics in homogeneous solution is propagated by a process where the Cu(II) ligand-radical precursors react with [Cu^II(H_x(tmdnTAA))]^x+.     

Influence of coanions on construction of copper(II)/4,4′-dipyridyl sulfide(dps) coordination polymers

The influence of coanion on self-assembly of CuSO₄ and 4,4′-dipyridyl sulfide (dps) was studied in this paper. During the formation of Cu(II)/dps coordination polymers, coanions Cl⁻, SCN⁻ and were added in the solution respectively. Three novel coordination polymers were obtained, {[Cu(dps)₂ · (SO₄)₂][Cu(dps) · Cl · (H₂O)₂]₂ · 12H₂O}_n (1 · 12H₂O, a 3D network), {[Cu(SCN)₂(dps)(CH₃OH)₂][Cu(dps)₂ · SO₄][Cu(dps)(CH₃CH₂OH)₂ · SO₄] · 5H₂O}_n (2 · 5H₂O, a 3D network), and {[Cu(dps)₂(H₂O)₂] · (PF₆)₂ · 3H₂O}_n (3 · 3H₂O, a 2D lattice network). Different coanion shows different influence on framework construction. In 1 and 2, Cl⁻ and SCN⁻ act as terminal ligands and similar 3D frameworks were composed of [Cu(dps)] layer with larger cavity (ca. 400 Å) and sulfate bridge; in 3, replaces entirely and the 3D framework was broken due to the removal of bridging anions. However, a 2D [Cu(dps)]₄ undulating grid was preserved in 3.     

Layered iron(II) spin crossover complex constructed by NH?Br hydrogen bonds with 2 K wide thermal hysteresis, [FeH3L]Br·CF3SO3 (H3L = tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine)

A series of compounds [Fe^IIH₃L^Me]Br·Y·nMeOH ( (1), (2), (3), (4); n = 0 or 1) were synthesized, where H₃L^Me is a hexadentate N₆ tripodal ligand of the neutral form, tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine, and their structures and magnetic properties were investigated. The compounds 1−3 with counter anions , , and contain methanol as a crystal solvent, and show no SCO behaviors, while the corresponding Cl⁻ compounds have no crystal solvent and show a variety of SCO behaviors. The compound [Fe^IIH₃L^Me]Br·CF₃SO₃ (4) has no crystal solvent and has isomorphous structure to the Cl⁻ compounds, and shows an abrupt spin transition between the HS (S = 2) and LS (S = 0) states with a hysteresis about 2 K and large frozen-in effect below 72 K. The T_1/2↑ and T_1/2↓ values are 98 and 96 K, whose values are higher than those of corresponding Cl⁻ compound about 15 K and the width of hysteresis is narrower than that of corresponding Cl⁻ compound about 2 K. The crystal structures of 4 were determined at 296 and 93 K, where the crystal system and space group showed no change between these temperatures. The structures at both temperatures have a same 2D layered structure, which is composed of NH?Br⁻ hydrogen bonds between the Br⁻ ion and the imidazole NH groups of three neighboring cations [Fe^IIH₃L^Me]²⁺. This network structure is the same as that of corresponding Cl⁻ compound. The 600 nm light irradiation at 5 K induced the LIESST effect.     

Anionic effects on the formation of tridentate 4′-chloro-2,2′:6′,2″-terpyridine copper(II) complexes having 1:1 or 1:2 ratio of metal and ligand and their crystal symmetry

A facile synthetic procedure has been used to prepare one five-coordinate and four six-coordinate copper(II) complexes of 4′-chloro-2,2′:6′,2″-terpyridine (tpyCl) ligand with different counterions (, , , , and ) in high yields. They are formulated as [Cu(tpyCl-κ³N,N′,N′′)(SO₄-κO)(H₂O-κO)] · 2H₂O (1), trans-[Cu(tpyCl-κ³N,N′,N″)(NO₃-κO)₂(H₂O-κO)] (2), [Cu(tpyCl-κ³N,N′,N″)₂](BF₄)₂ (3), [Cu(tpyCl-κ³N,N′,N″)₂](PF₆)₂ (4) and [Cu(tpyCl-κ³N,N′,N″)₂](ClO₄)₂ (5) and versatile interactions in supramolecular level including coordinative bonding, O-H?O, O-H?Cl, C-H?F, and C-H?Cl hydrogen bonding, π-π stacking play essential roles in forming different frameworks of 1-5. It is concluded that the difference of coordination abilities of the counterions used and the experimental conditions codominate the resulting complexes with 1:1 or 1:2 ratio of metal and ligand.     

Ruthenium(II) complexes possessing the η-p-cymene ligand

Complexes possessing a soft donor η⁶-arene and hard donor acetylacetonate ligand, [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1) (OTf = trifluoromethanesulfonate; acac = acetylacetonate) and {Ar′ = 3,5-(CF₃)-C₆H₃}, were prepared and fully characterized. The lability of the μ-CH linkage for complex 1 and the THF ligand of 2 allow access to the unsaturated cation [(η⁶-p-cymene)Ru(κ²-O,O-acac)]⁺. The reaction of with KTp {Tp = hydridotris(pyrazolyl)borate} produces . The azide complex forms upon reaction of with N₃Ar (Ar = p-tolyl), and reaction of with CHCl₃ at 100 °C yields the chloride-bridged binuclear complex . The details of solid-state structures of [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1), and are disclosed.     

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.     

Kinetics and mechanism of the oxidation of oxalic acid by tetrachloroaurate(III) ion

The oxidation of oxalic acid by tetrachloroaurate(III) ion in 0.005 ? [HClO₄] ? 0.5 mol dm⁻³ is first order in and a fractional order in [oxalic acid], the reactive entities being AuCl₃(OH)⁻ and ions. The pseudo first-order rate, k_obs, with respect to [Au(III)], is retarded by increasing [H⁺] and [Cl⁻]. The retardation by H⁺ ion is caused by the dissociation equilibrium . A mechanism in which a substitution complex, is formed from AuCl₃(OH)⁻ and ions prior to its rate limiting disproportionation into products is suggested. The rate limiting constant, k, has been evaluated and its activation parameters are reported. The equilibrium constant K₁ for the formation of the substitution complex and its thermodynamic parameters are also reported.     

Interaction of gold(I) with thiosulfate-sulfite mixed ligand systems

The system was studied at 25 °C and at I = 0.1 M NaClO₄ using hydrodynamic voltammetry, gold potentiometry, UV-Vis spectrophotometry and Raman spectroscopy. The presence of two mixed-ligand species, Au(S₂O₃)(SO₃)³⁻ and , was detected from the Raman experiments and supported by the gold potentiometric experiments. The stepwise formation constant, log K_11r, for the reaction was found to be 1.1 (r = 1) and 4.8 (r = 2) from the hydrodynamic voltammetric experiments.     

Redox chemistry of copper complexes of 6,7-dicyanodipyridoquinoxaline: A pulse radiolysis study

A series of copper (II) complexes having the general formula Cu(phen)_n(dicnq)_2−nCl₂ (n = 0,1,2) (1,10-phenanthroline (phen) and/or 6,7-dicyanodipyridoquinoxaline (dicnq) were synthesized and characterized by optical, elemental analysis and IR. The reactions of oxidizing (OH) and reducing () radicals with these complexes were studied by pulse radiolysis. Their absorption spectra have bands in the UV region (?350 nm) consisting of an intense π → π∗ transition due to the ligands (ε ∼ 10⁵ dm³ mol⁻¹ cm⁻¹) and weak MLCT (dπ → π∗) band in the visible region and are non-luminescent. The OH radical reacts with all complexes at diffusion controlled rates and reacts by addition to the ligands and in the case OH adduct of Cu(dicnq)₂Cl₂, an intramolecular charge transfer followed deprotonation resulting in Cu(I) complex was noticed. The rates of reaction of with Cu(II) complexes are high (k ≈ 10¹⁰ dm³ mol⁻¹ s⁻¹) and the transient spectra show absorption maximum at 440 nm indicating reduction of Cu(II) to Cu(I).     

Trichloroacetic acid dehalogenation by reductive radicals

Advanced oxidation processes, using either UVC/H₂O₂ or UVC/K₂S₂O₈, both in the presence of H₂CO₂ or CH₃OH are very efficient in mineralizing aqueous solutions of trichloroacetic acid (TCAA) leaving no toxic residues. The main reaction initiating TCAA depletion is its reduction by the radicals or CH₂OH to yield radicals and Cl⁻ anions. Further thermal reactions of lead to the formation of CO₂ and HCl. Molecular oxygen competes with TCAA for and CH₂OH radicals. However, in experiments under continuous irradiation of initially air-saturated solutions in closed reactors, the dissolved molecular oxygen concentration was depleted to low enough levels to favor the reaction of the reducing radicals with TCAA. A general reaction mechanism is proposed and discussed. The reaction between superoxide radical anions and TCAA was found to be of low efficiency.