Syntheses, structures and bioactivities of silver(I) complexes with dithioether ligands that contain a di- or triethylene glycol chain and different terminal groups

A series of flexible dithioethyl ligands that contain ethyleneoxy segments were designed and synthesized, including bis(2-(pyridin-2-ylthio)ethyl)ether (L¹), 1,2-bis(2-(pyridin-2-ylthio)ethoxy)ethane (L²), bis(2-(benzothiazol-2-ylthio)ethyl)ether (L³) and 1,2-bis(2-(benzothiazol-2-ylthio)ethoxy)ethane (L⁴). Reactions of these ligands with AgNO₃ led to the formation of four new supramolecular coordination complexes, [Ag₂L¹(NO₃)₂]₂ (1), [Ag₂L²(NO₃)₂] (2), [AgL³(NO₃)]_∞ (3) and [AgL⁴(NO₃)] (4) in which the length of the (CH₂CH₂O)_n spacers and the terminal groups of ligands cause subtle geometrical differences. Studies of the inhibitory effect to the growth of Phaeodactylum tricornutum show that all four complexes are active and the compound 4 has the highest inhibitory activity.     

Synthesis, structures and conductivity properties of silver 3-sulfobenzoate coordination polymers

Four coordination polymers based on Ag^I/3-sulfobenzoate/N-donor ligands, [Ag₂Na₂(3-sb)₂(H₂O)₇]_n (1), {[Ag₂(3-sb)(apy)]·(H₂O)}_n (2), {[Ag₂(4,4′-bipy)₂(H₂O)₃]·[Ag₂(4,4′-bipy)₂(H₂O)₂]·2(3-sb)·4(H₂O)}_n (3) and {[Ag(3-sb)(bpe)(H₂O)][Ag(bpe)(H₂O)]·3(H₂O)}_n (4) where 3-sb is 3-sulfobenzoate, apy is 2-aminopyridine, bipy is 4,4′-bipyridine and bpe is 1,2-bis(4-pyridyl)ethylene, were prepared and characterized, and their fluorescence and electric conductivity properties were studied. Complex 1 is a 3D architecture in which 3-sb ligands exhibit μ₄-κ¹(O1,O2-Ag): κ¹(O3,O5-Na) trans-trans coordination mode. The molecular structure of 2 is a 2D layer. Complexes 3 and 4 are cation-anion species and 1D polymers. In these complexes hydrogen bonds provide additional assembly forces, giving 3D hydrogen bonding networks for 1 and 3, and 2D layers for 2 and 4. Abundant weak interactions, such as Ag-Ag interactions in 1-3, Ag-π interactions in 1-4, π-π interactions in 1, 3-4, and C-H···π interactions in 3-4, also can be found. The weak interactions are strongly related to the fluorescence and electric conductivity properties, providing the way for understanding the relationship between structures and properties.     

One-step synthesis and reduction of triphenylphosphine carbonyl palladium clusters of variable nuclearities

Heteroleptic triphenylphosphine carbonyl palladium clusters of different nuclearities were prepared under mild conditions by only varying the amount of ligand (PPh₃) used in the synthesis: three different clusters were successfully isolated after CO bubbling in a solution of [Pd₂(dba)₃] (dba = dibenzylideneacetone) with 3, 1 or 0.5 equiv of PPh₃, which led, respectively, to [Pd₄(CO)₅(PPh₃)₄] (1), [Pd₁₀(CO)₁₂(PPh₃)₆] (2) and [Pd_n(CO)_x(PPh₃)_y] (3) (n ≈ 24). The molecular structures of compounds 1 and 2 were determined by X-ray crystallography. The metal cores in these compounds were shown to consist in a butterfly for 1 and a bridged octahedron for 2. Compound 3 was shown to be at the boundary between molecular clusters and colloidal particles with tentative formulation arising from characterization data. These three clusters and the known [Pd₁₀(CO)₁₂(PBu₃)₆] and [Pd₁₂(CO)₁₅(PBu₃)₇] were submitted to NaBH₄ reduction. The Pd₄ cluster 1 did not react. The colloidal Pd_n species led to no isolable product. By contrast, the two Pd₁₀ and the Pd₁₂ clusters led to reduction products, isolated as salts. In the case of the reduced Pd₁₂ cluster, its structure was resolved by X-ray crystallography: the metal core consists of a face-capped octahedron. The reduced species reacted readily with Au(PPh₃)⁺, confirming their anionic nature.     

Tunable polymerization of silver complexes with organosulfur ligand: counterions effect, solvent- and temperature-dependence in the formation of silver(I)-thiolate(and/or thione) complexes

The reaction of pyridine-2-thiol with AgBF₄ and AgClO₄ in MeCN gave rise to polymeric compounds [{Ag(HPyS)₂}₂(BF₄)₂]_n (1) and [{Ag(HPyS)₂}₂(ClO₄)₂]_n (2) (HPyS=pyridine-2-thione), respectively, while the similar reaction of pyridine-2-thiol with AgNO₃ resulted in a polymeric compound [{Ag₄(HPyS)₆}(NO₃)₄]_n (3). X-ray single-crystal diffraction analyses showed that the cations of both 1 and 2 possess a single-metal-atom chain structure but that of 3 is a double-metal-atom chain structure. The difference between 1 (or 2) and 3 showed counterion effect in polymerization of silver-thione compounds. In the presence of water, the treatment of pyridine-2-thiol with AgBF₄ in DMF at 0 °C generated a polymeric compound [Ag(SPy)]_n (4) (Spy=pyridine-2-thiolate) with graphite-like layered array of silver ions. Compound 4 can convert into its isomer [Ag₆(SPy)₆]_n (5) through soaking in DMF for 1 month. However, the similar reaction of pyridine-2-thiol with AgBF₄ in MeCN-H₂O (v:v=40:1) at room temperature gave another layered polymeric compound [{Ag₅(Spy)₄(HPyS)}BF₄]_n (6). The preparation of 4, 5, and 6 showed that temperature and solvent exert influence on formation of silver-thiolate polymers. The reaction of AgNO₃ with K₂i-mnt (i-mnt=2,2-dicyanoethene-1,1,-dithiolate) and pyridine-2-thiol gave a polymer [Ag₄(μ₄-i-mnt)₂(μ-HPyS)₂(μ-HPyS)_4/2]_n (7) with one-dimensional (1-D) chain structure consisting of Ag₄ square planar cluster units linked by 1H-pyridine-2-thione ligand. The treatment of AgNO₃ with NaS₂CNEt₂ and pyridine-2-thiol in DMF resulted in another polymeric compound [Ag₄(μ₃-S₂CNEt₂)₂(μ₂-SPy)_4/2]_n (8). The preparation and characterization of these polymeric compounds demonstrated that polymerization of silver(I)-thione and silver(I)-thiolate complexes is tunable through controlling reaction conditions. Semiconducting property studies of 1-8 demonstrated that the electrical conductivity of 4 is 2.04×10⁻⁵ S cm⁻¹ at 25 °C and increases as temperature rises, and those of 1-3 and 5-8 are in the range of 1×10⁻¹²-1×10⁻¹⁵ S cm⁻¹ at room temperature and independent on the temperature, indicating that 1 is a semiconductor and the others are insulators.     

Conformation-sensitive molecular pendulums: variable temperature NMR study of dimeric palladium(I) bisphosphine complexes

Solution and solid state ³¹P NMR studies were carried out on a series of [Pd₂X₂(dppm)₂] (X = Cl (1a), Br (1b), I (1c)), or [Pd₂XY(dppm)₂] (X = Cl, (1d)) complexes and on methyl substituted derivatives such as [Pd₂Cl₂(dppm)(dppmMe)] (2), syn-[Pd₂Cl₂(dppmMe)₂] (3), and anti-[Pd₂Cl₂(dppmMe)₂] (4) (dppmMe = 1,1-bis(diphenylphosphino)ethane) in order to study and understand the conformational behaviour of the eight-membered Pd₂P₄C₂ rings depending on the substituents and their stereochemistry. These complexes with metal-metal bonds and mutually trans-dppm ligands act as molecular pendulums. On the basis of temperature dependent spectra qualitative correlations have been found between the molecular conformations and the rate of a specific intramolecular motion called “swinging”. While for the extended-boat conformers (2 and 3) this exchange process is of intermediate energy (41-45 kJ mol⁻¹), the barrier is definitely higher (∼54 kJ mol⁻¹) for the extended-chair conformer 4. Changes of symmetry relations are reflected very vividly in the ³¹P NMR spectra.The observed different chemical shifts, “swinging” rates and activation free energies obtained for the boat and chair conformers are explained by the steric effects and low-temperature conformations of the axial phenyl groups.     

Assembly of 1D, 2D and 3D silver(I) coordination polymers with nitrilotriacetate and 2-aminopyrimidyl mixed ligands

Three mixed ligands coordination polymers (CPs) [Ag_1.5(apym)(nta)_0.5]_n (1), [(NH₄)Ag₂(mapym)(nta)·(H₂O)₃]_n (2), [Ag₂(dmapym)₃(Hnta)]_n (3) (apym = 2-aminopyrimidine, mapym = 4-methyl-2-aminopyrimidine, dmapym = 4, 6-dimethyl-2-aminopyrimidine, H₃nta = nitrilotriacetate) were synthesized and characterized. For 1-3, as the substituents change from H to one methyl and two methyl groups, the dimensionalities of 1-3 decrease from three-dimension (3D) to one-dimension (1D) due to the steric effect of methyl groups. For 1, the μ₂-apym ligands link the Ag(I) ions to form a 1D double-chain incorporating ligand unsupported Ag···Ag interaction. The nta³⁻ ligands extend the 1D double-chain into a 3D framework. In 2, one heptadentate nta³⁻ ligand binds four Ag(I) ions and incorporates μ₂-mapym ligand to link metal centers to form a 2D sheet which can be simplified to be a 10³ net. Complex 3 features a 1D chain structure incorporating Hnta²⁻ and monodentate dmapym ligands. The substituents on the pyrimidyl ring intensively influence the coordination environments of metal ion and the coordination modes of the carboxyl group, and thus determine the structures of the CPs. The photoluminescent properties of 1-3 were also investigated.     

Assembly of luminescent Ag(I) coordination architectures adjusted by modification of pyrimidine-based thioether ligands

Two new structurally related pyrimidine-based thioether ligands, angular ditopic ligand 1,3-bis(2-pyrimidinylthiomethyl)benzene (L²) and linear ditopic ligand 1,4-bis(2-pyrimidinylthiomethyl)benzene (L³), have been designed and prepared. Reaction of two shaped-specific ligands with different silver(I) salts affords three novel luminescent coordination architectures: discrete metallomacrocycle [Ag₄(L²)₂(NO₃)₄] · 2MeOH (3), 1D chain {[Ag₂L³(NO₃)₂] · 2CCl₃}_n (4) and 2D wire netlike structure {[AgL³(DMF)]ClO₄ · 0.25H₂O}_n (5). The results show that the nature of organic ligands, geometric requirement of metal atoms and counter anions have great influence on the structures of metal-organic frameworks.     

Silver decoration of a palladacycle through “spacer-guest” interaction

[Pd(dppf)(MeCN)₂](OTf)₂ [dppf = 1,1′-bis(diphenylphosphino)ferrocene, OTf = triflate] reacts with pyridyl acetic acid (PyAcOH) to yield a dipalladium ring structure, [Pd₂(dppf)₂(μ-PyOAc)₂](OTf)₂ (1). The doubly-bridging ligands exhibit basicity at the pendant carboxyl oxygen to attract AgX (X = OTf or CF₃CO₂) to form [Pd₂Ag₂(dppf)₂(PyOAc)₂(OTf)₄] (2) and [Pd₂Ag₂(dppf)₂(PyOAc)₂(OTf)₂(CF₃CO₂)₂] (3), respectively. Complexes 1 and 2 have been crystallographically characterized. Similar spacer-guest affinity is not found in the Pt(II) or isonicotinate analogues.     

Palladium(II) and platinum(II) complexes with polypyridylbenzene ligands

The ligands 1,3-bis(3-pyridyl)benzene (1), 1,3-bis(4-pyridyl)benzene (2) and 1,3,5-tris(4-pyridyl)benzene (3) have been prepared by Stille coupling of 3- or 4-trimethylstannylpyridine with the appropriate bromoarene. Ligands 1 and 2 react with [M(OTf)₂(dppp)] (M=Pd, Pt) to produce the dipalladium- or diplatinum-containing macrocycles [M₂(μ-1)₂(dppp)₂](OTf)₄ or [M₂(μ-2)₂(dppp)₂](OTf)₄. These have been characterized by NMR spectroscopy and mass spectrometry and, in the case of [Pd₂(μ-1)₂(dppp)₂](OTf)₄, by X-ray crystallography. The molecular structure of the [Pd₂(μ-1)₂(dppp)₂]⁴⁺ cation reveals a shallow arrangement of the aromatic rings, with the palladium atoms lying above and below. The tridentate ligand 3 reacts with [Pd(OTf)₂(dppp)] to produce a trimetallic species of the form [Pd₃(μ₃-3)₂(dppp)₃](OTf)₆.     

Synthesis and structural characterisation of new mono and dinuclear pyrazolatopalladium (II) complexes self-assembled through robust hydrogen-bonds

This work describes the reactivity of compounds [Pd(dmpz)₂(Hdmpz)₂] (A) (dmpz = 3,5-dimethylpyrazolate, Hdmpz = 3,5-dimethylpyrazol) and [Pd₂(μ-dmpz)₂(dmpz)₂(Hdmpz)₂] (B) towards several dicarboxylic acids and also towards perchloric acid. The compounds [Pd(Hdmpz)₄](O₂C-(CH₂)_n-CO₂H)₂ [n = 1 (1), 3 (2)] have been obtained by treatment of [Pd(dmpz)₂(Hdmpz)₂] (A) with two equivalents of malonic (HO₂C-CH₂-CO₂H) and glutaric (HO₂C-(CH₂)₃-CO₂H) acids. The X-ray study on a crystal of [Pd(Hdmpz)₄](O₂C-(CH₂)₃-CO₂H)₂ (2) revealed that the glutarate anions link to the cationic complex [Pd(Hdmpz)₄]²⁺ through the carboxylate group by charge-assisted N-H⁽⁺⁾?O⁽⁻⁾ hydrogen bonds. Additionally, the carboxylate anions form uncommon dimeric rings on both sides of the metal complex via a pair of O-H?O hydrogen bonds, yielding a hydrogen bonded polymeric chain with alternating inorganic [Pd(Hdmpz)₄]²⁺ and organic fragments. The dinuclear complexes [Pd₂(μ-dmpz)₂(O₂C-(CH₂)_n-CO₂)(Hdmpz)₂] [n = 0 (5), 1 (6)] were obtained from equimolar amounts of [Pd₂(μ-dmpz)₂(dmpz)₂(Hdmpz)₂] (B) and the corresponding dicarboxylic acid, HO₂C-(CH₂)_n-CO₂H (n = 0, 1). However, the synthesis of 5 and 6 requires two steps, the protonation of both terminal dmpz groups in B with HClO₄ to give [Pd₂(μ-dmpz)₂(Hdmpz)₄](ClO₄)₂ (4) and the subsequent treatment of this cationic palladium complex with salts of the corresponding dicarboxylic acids. The X-ray structures of compounds 5 and 6 are reported. Both in 5 and 6, the Pd₂N₄ ring shows a typical boat-like conformation and the metal atoms are separated in about 3.3 Å. Both 5 and 6 are asymmetric and contain two Hdmpz groups - H-bond donors - at one end, and two CO groups from the dicarboxylate anion - H-bond acceptors - at the other, in such a way that the donor end of one molecule links with the acceptor end of its neighbour forming a hydrogen-bonded polymeric chain. The synthesis and X-ray study of compounds [Pd(Hdmpz)₄](ClO₄)₂ (3) and [Pd₂(μ-dmpz)₂(Hdmpz)₄](ClO₄)₂ (4), obtained by reaction of [Pd(dmpz)₂(Hdmpz)₂] (A) and [Pd₂(μ-dmpz)₂(dmpz)₂(Hdmpz)₂] (B) with two equivalents of perchloric acid, are also reported.     

Coordination behavior of phosphino-phosphaferrocenes: monodentate versus bidentate coordination to divalent palladium

Two novel phosphino-phosphaferrocenes [η⁵-C₅H₄(CH₂)_nPPh₂]Fe(η⁵-PC₄H₂-2,5-Cy₂) (PP1: n=1; PP2: n=2) have been designed and prepared in order to clarify weak chelate effect in the previously reported (η⁵-C₅H₄CH₂PPh₂)Fe[η⁵-PC₄H₂-2,5-((-)-menthyl)₂] (1). ³¹P NMR studies of reactions of PP1 with PdCl₂(cod) (6) revealed that PP1 showed stronger tendency to coordinate to the Pd^II center in bidentate fashion compared to 1. On the other hand, chelate effect in PP2 was negligibly weak and a reaction of PP2 with 6 in a PP2/6 = 2/1 molar ratio gave a complex PdCl₂(PP2)₂ (10) cleanly in which PP2 coordinated to the palladium center at the PPh₂ moiety as a monodentate ligand. X-ray crystal structure studies of chelate complexes PdCl₂(PP1) (7) and PdCl₂(PP2) (9) showed that 9 had deviations from an idealized geometry in the square planar complex which could be attributed to a larger chelate ring of PP2, while PP1 in 7 constructed nearly ideal geometry for the square planar complex.From comparison of the coordination behavior between 1, PP1, and PP2, it is concluded that steric bulk of (-)-menthyl groups in 1 is the main factor of the weak chelate coordination of 1.     

Anion-controlled four silver coordination polymers with flexible bis(1,2,4-triazol-4-yl)ethane

The self-assembly reaction of the flexible ligand 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) and Ag salts with BF₄⁻, SO₄²⁻, NO₃⁻ and ClO₄⁻ gives novel coordination polymers {[Ag(btre)₂](BF₄)}_n (1), {[Ag₂(btre)_1.5(H₂O)](SO₄)·5H₂O}_n (2), {[Ag(btre)](NO₃)·H₂O}_n (3) and {[Ag(btre)](ClO₄)}_n (4). The structure of 1 is a one-dimensional double chain through double bis-monodentate btre bridges. Compound 2 is a novel two-dimensional network containing the Ag₄ unit node and μ₄-btre building block. In 3 and 4, adjacent two silver(I) atoms are linked through four nitrogen atoms of two N1/N2 atoms of two btre ligands and form Ag₂N₄ 6-membered rings and construct a one-dimensional chain. The chains extends through btre bridges in four different directions alternatively to construct a novel three-dimensional network. The luminescences of 1-4 were observed in the solid state at room temperature. Compounds 3 and 4 are inversely transfered by the anion exchange procedure.     

Preparation and characterization of dinuclear palladium tetraamin-thiophenolate complexes coligated by bridging acetate and acetamidate units

The aromatic thioether (2,6-bis((2-(dimethylamino)ethylamino)methyl)phenyl)(tert-butyl)sulfane (6) reacts with [Pd(NCCH₃)₂Cl₂] under S-C bond cleavage to give the dinuclear palladium(II) complex [L³Pd₂(μ-Cl)]²⁺ (7), where (L³)⁻ = 2,6-bis((2-(dimethylamino)ethylamino)methyl)-thiophenolate. Complex 7 reacts readily with sodium acetate and sodium acetamide by the displacement of the bridging chloride group forming [L³Pd₂(μ-OAc)]²⁺ (8) and [L³Pd₂(μ-ONHCCH₃)]²⁺ (9), respectively. Complex 8 can also be prepared by the reaction of 6 with [Pd(OAc)₂]. All complexes were isolated as perchlorate salts and fully characterized by ESI-MS, IR, ¹H, and ¹³C NMR spectroscopy. The structures of 7[ClO₄] and 9[ClO₄]₂ have been determined by X-ray crystallography. The latter structure reveals a μ_1,3-bridging acetamidate unit showing that (L³)⁻ can alter its conformation sufficiently to accommodate a multi-atom bridging species between the two Pd atoms.     

Syntheses, crystal structures and luminescent properties of two silver complexes of N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine

Treatment of a suspension of AgNO₃ and AgCl in MeOH with a solution of N,N,N′,N′-tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda) in CHCl₃ afforded a binuclear complex [Ag₂(dppeda)Cl](NO₃)·2MeOH (1). The analogous reactions using AgSCN and dppeda in EtOH/CH₂Cl₂ gave rise to a polymeric complex [Ag₂(dppeda)(SCN)₂]_n (2). Both compounds were fully characterized by elemental analyses, IR spectra, ¹H(³¹P) NMR, and single-crystal X-ray crystallography. The cation of 1 shows an interesting molecular basket framework in which dppeda adopts a side-by-side coordination mode. Compound 2 possesses an unique 2D (6,3) layer network with 34-membered metallomacrocycles in which dppeda takes a end-to-end coordination mode. The 2D topological framework of 2 is rare in the chemistry of tetraphosphines. The photoluminescent properties of 1 and 2 in solid state at ambient temperature were investigated.     

Structures, fluorescent properties of the Ag(I) compounds based on molecular clips with biphenyl core

Three silver complexes Ag₂(L)₂(NO₃)₂ (1), Ag₂(L)₂(SO₃CF₃)₂(H₂O)_0.5 (2), and [Ag₂(L)₂(NO₃)₂]_n (3) were prepared from molecular clips, 2,2′-Bis(imidazol-1-ylmethyl)-biphenyl (L) and structurally characterized to investigate the structural-luminescent relation. Compound 1 is a bimetallic supramolecular rectangle in which two L ligands are connected by two linearly coordinated Ag(I) ions. Compound 2 is described as a double helicate due to the nature of the twist of the imidazole groups after coordination to Ag(I) centers. In compound 3, the Ag(I) centers are connected by L ligands into a one-dimensional zigzag chain. Solid state and solution fluorescent measurements exhibit the presence of ligand-based emission at 415 and 435 nm of compounds 1 and 2, respectively. It is said that the dihedral angles between the two imidazole rings coordinated to one Ag(I) center affect the emission properties.     

Nanopowders of 3D Ag coordination polymer: A new precursor for preparation of silver nanoparticles

Nanopowders of novel three-dimensional Ag^I coordination polymer, [Ag₂(μ₈-SB)]_n (1) [H₂SB = 4-[(4-hydroxyphenyl)sulfonyl]-1-benzenol] has been synthesized by the reaction of SB²⁻ and AgNO₃ by a sonochemical method. Reaction conditions, such as the concentration of the initial reagents and power of the ultrasonic device played important roles in the size, morphology and growth process of the final products. For the first time silver nanoparticles were synthesized from [Ag₂(μ₈-SB)]_n (1) coordination polymer by calcinations and hydrothermal methods. These nanopowders and nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM); transmission electron microscopy (TEM) and energy-dispersive X-ray spectra (EDS). Thermal stability and emission properties of nano and crystal samples of compound 1 were studied and compared with each other.     

New pyridyl modified phosphines: Synthesis and late transition-metal coordination studies

Using a phosphorus based Mannich condensation reaction the new pyridylphosphines {5-Ph₂PCH₂N(H)}C₅H₃(2-Cl)N (1-Cl) and {2-Ph₂PCH₂N(H)}C₅H₃(5-Br)N (1-Br) have been synthesised in good yields (60% and 88%, respectively) from Ph₂PCH₂OH and the appropriate aminopyridine. The ligands 1-Cl and 1-Br display variable coordination modes depending on the choice of late transition-metal complex used. Hence P-monodentate coordination has been observed for the mononuclear complexes AuCl(1-Cl) (2), AuCl(1-Br) (3), RuCl₂(p-cymene)(1-Cl) (4), RuCl₂(p-cymene)(1-Br) (5), RhCl₂(Cp^∗)(1-Cl) (6), RhCl₂(Cp^∗)(1-Br) (7), IrCl₂(Cp^∗)(1-Cl) (8), IrCl₂(Cp^∗)(1′-Cl) (8′), IrCl₂(Cp^∗)(1-Br) (9), cis-/trans-PdCl₂(1-Cl)₂ (10), cis-/trans-PdCl₂(1-Br)₂ (11), cis-PtCl₂(1-Cl)₂ (12) and cis-PtCl₂(1-Br)₂ (13). Reaction of Pd(Me)Cl(cod) (cod = cycloocta-1,5-diene) with either 1 equiv. of 1-Br or the known pyridylphosphines 1′-Cl, 1-OH or 1-H gave the P/N-chelate complexes Pd(Me)Cl(1-Br-1-H) (14)-(17). All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 4, 5, 10 and 16 · (CH₃)₂SO have been elucidated by single crystal X-ray crystallography. A crystal structure of the dinuclear metallocycle trans,trans-[PdCl₂{μ-P/N-{Ph₂PCH₂N(H)}C₅H₄N}]₂ · CHCl₃, 18 · CHCl₃, has also been determined. Here 1-H bridges, using both P and pyridyl N donors, two dichloropalladium centres affording a 12-membered ring with the PdCl₂ units adopting a head-to-tail arrangement.     

Synthesis and characterisation of pyrazolic palladium compounds containing alcohol functionality:: rotation around the Pd-N bond

The ligands 1-hydroxymethylpyrazole (hl¹), 1-(2-hydroxyethyl)pyrazole (hl²) and 1-(3-hydroxypropyl)pyrazole (hl³) react with [PdCl₂(CH₃CN)₂] to give trans-[PdCl₂(hl)₂] compounds. Due to a hindered rotation around the Pd-bond, these compounds present two different conformations in solution: anti and syn. The conformation presented depends on the relative disposition of the hydroxyalkylic chains of the two pyrazolic ligands. The present study was carried out on the basis of NMR experiments. The present paper reports the crystal structure of trans-[PdCl₂(hl²)₂]. The synthesis and characterisation of compounds [Pd(hl)₄](BF₄)₂ (hl = hl¹, hl² and hl³) starting from [Pd(CH₃CN)₄](BF₄)₂ and the corresponding chlorocomplexes trans-[PdCl₂(hl)₂] are also described.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Two new polyoxometalate-based hybrids: Structural transformation played by a secondary bridging ligand

Two new Keggin polyoxometalate-based compounds, [Ag₄(phnz)₆(SiW₁₂O₄₀)] (phnz = phenazine) (1) and [Ag(phnz)_1.5][Ag(phnz)(pz)][{Ag₂(phnz)(pz)(H₂O)}(SiW₁₂O₄₀)] (2) (pz = pyrazine), have been hydrothermally synthesized. Compound 1 is a discrete cluster in which the [SiW₁₂O₄₀]⁴⁻ (SiW₁₂) anion symmetrically connects two dinuclear Ag₂(phnz)₃ fragments. All Ag^I in 1 adopt a trigonal geometry. By introducing the secondary bridging ligand “pz” into the above system, compound 2 was obtained. Compound 2 contains three kinds of silver complex subunits: [Ag₂(phnz)(pz)(H₂O)]²⁺, [Ag₂(phnz)₃]²⁺ and [Ag(phnz)(pz)]⁺. The first one extends to a wave-like chain with SiW₁₂ anions as bi-dentate suspenders, and the last two are counter cations. Furthermore, Ag^I ions in 2 exhibit three kinds of coordination modes. Their electrochemistry properties have also been studied.