(Pyrazolylmethyl)pyridine platinum(II) and gold(III) complexes: Synthesis, structures and evaluation as anticancer agents

Reactions of 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L1), 2-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L2), 2-(3,5-di-tert-butylpyrazol-1-ylmethyl)pyridine (L3) and 2-(3-p-tolylpyrazol-1-ylmethyl)pyridine (L4) with K₂[PtCl₄] in a mixture of ethanol and water formed the dichloro platinum complexes [PtCl₂(L1)] (1), [PtCl₂(L2)] (2), [PtCl₂(L3)] (3) and [PtCl₂(L4)] (4). Complex 1, [PtCl₂(L1)], could also be prepared in a mixture of acetone and water. Performing the reactions of L2 and L3 in a mixture of acetone and water, however, led to C-H activation of acetone under mild conditions to form the neutral acetonyl complexes [Pt(CH₂COCH₃)Cl(L2)] (2a) and [Pt(CH₂COCH₃)Cl(L3)] (3a). The same ligands reacted with HAuCl₄ · 4H₂O in a mixture of ethanol and water to form the gold salts [AuCl₂(L1)][AuCl₄] (5) [AuCl₂(L2)][Cl] (6) [AuCl₂(L3)][Cl] (7) and [AuCl₂(L4)][AuCl₄] (8); however, with the pyrazolyl unit in the para position of the pyridinyl ring in 4-(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L5), 4-(3,5-diphenylpyrazol-1-ylmethyl)pyridine (L6) neutral gold complexes [AuCl₃(L5)] (9) and [AuCl₂(L6)] (10) were formed; signifying the role the position of the pyrazolyl group plays in product formation in the gold reactions. X-ray crystallographic structural determination of L6, 2, 33a, 8 and 10 were very important in confirming the structures of these compounds; particularly for 3a and 8 where the presence of the acetonyl group confirmed C-H activation and for 8 where the counter ion is . Cytotoxicity studies of L2, L4 and complexes 1-10 against HeLa cells showed the Au complexes were much less active than the Pt complexes.     

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.     

Addition of secondary amines to activated alkenes promoted by Pd(II) complexes: Use of ammonium salts as cocatalysts

The complexes [Pd(acac)₂] 1, [Pd(hfa)₂] 2 (hfa = hexafluoroacetylacetonate), [Pd(CF₃CO₂)₂] 3 and [Pd₃(CH₃CO₂)₆] 4 exhibit very different catalytic efficiency in the reaction between secondary amines and activated alkenes. Complexes 1 and 4 generally show an enhanced activity when catalytic amounts of NH₄X salts (X⁻ = low-coordinating anion) are added to the reaction mixtures. On the contrary, the activity of the perfluorurate analogues 2 and 3, which is much higher than that of 1 and 4, is generally scarcely affected by the presence of the NH₄X additive. The cocatalytic effect of NH₄X is comparable with that of strong acids such as CF₃SO₃H. The ammonium salts alone can behave as a catalyst giving an almost quantitative yield of the hydroamination product.     

Synthesis and characterization of amine complexes of the cyclopentadienyliron dicarbonyl complex cation, [Cp(CO)2Fe]

The organometallic Lewis acid, [CpFe(CO)₂]⁺ (Cp = η⁵-C₅H₅) reacts with excess dry diethyl ether at low temperatures to form the labile complex [CpFe(CO)₂(Et₂O)]⁺[BF₄]⁻ (1) which is stable at low temperatures and has been fully characterized. Complex 1 in turn reacts with 1-aminoalkanes and α,ω-diaminoalkanes to form new complexes of the type [CpFe(CO)₂NH₂(CH₂)_nCH₃]BF₄ (n = 2-6) (2) and [{CpFe(CO)₂}₂μ-(NH₂(CH₂)_nNH₂)](BF₄)₂ (n = 2-4) (3), respectively. These complexes have been fully characterized and the mass spectral patterns of complexes 2 are reported. The structures of compounds 2a (n = 2) and 2b (n = 3) have been confirmed by single crystal X-ray crystallography. The single crystal X-ray diffraction data show that complex 2a, [CpFe(CO)₂NH₂(CH₂)₂CH₃]BF₄, crystallizes in a triclinic space group while 2b, [CpFe(CO)₂NH₂(CH₂)₃CH₃]BF₄, crystallizes in an orthorhombic Pca2₁ space group with two crystallographically independent molecular cations in the asymmetric unit. Furthermore, the reaction of 1 with 1-alkenes gives the η²-alkene complexes in high yield.     

Synthesis of amidate-hanging platinum mononuclear complexes by base hydrolysis of nitrile complexes

The “amidate-hanging” Pt mononuclear complexes, which can easily bind a second metal ion with the non-coordinated oxygen atoms in the amidate moieties, have been synthesized and characterized by ¹H NMR, MS, IR spectroscopy, and single crystal X-ray analysis. Five new complexes with various amidate ligands and co-ligands, cis-[Pt(PVM)₂(en)] · 4H₂O (1, PVM = pivaloamidate, en = ethylenediamine), cis-[Pt(PVM)₂(NH₂CH₃)₂] · H₂O (2), cis-[Pt(PVM)₂(NH₂^tBu)₂] (3), cis-[Pt(TCM)₂(NH₃)₂] (4, TCM = trichloroacetamidate), and cis-[Pt(BZM)₂(NH₃)₂] (5, BZM = benzamidate), were successfully synthesized by direct base hydrolysis of the corresponding Pt nitrile complexes, cis-[Pt(NCR)₂(Am)₂]²⁺ (P1, P2, P3, and P5) (NCR = nitrile, Am = amine). These nitrile complexes were obtained by introducing nitriles into the Pt aqua complexes, cis-[Pt(OH₂)₂(Am)₂](ClO₄)₂, whereas introduction of trichloronitrile into [Pt(OH₂)₂(NH₃)₂](ClO₄)₂ induced more facilitated water nucleophilic attack to afford [Pt(TCM)(NH(COH)CCl₃)(NH₃)₂](ClO₄) (P4). The base treatments of the precursor complexes (P1-5) lead to produce “amidate-hanging” Pt mononuclear complexes (1-5) without geometry isomerization. The ¹⁹⁵Pt chemical shifts for 1-5 exhibit subtle differences of the Pt electron densities among them.     

Potential new inorganic antitumour agents from combining the anticancer traditional Chinese medicine (TCM) matrine with Ga(III), Au(III), Sn(IV) ions, and DNA binding studies

Three new compounds of Ga(III), Au(III), Sn(IV) with matrine (MT), [H-MT][GaCl₄] (), [H-MT][AuCl₄] () and [Sn(H-MT)Cl₅] (), have been synthesized and characterized by elemental analysis, IR, ESI-MS and single crystal X-ray diffraction methods. The crystal structural analyses indicate that 1 and 2 are ionic compounds, whereas 3 is a tin(IV) complex formed by the monodentate MT via its carbonyl oxygen atom of MT coordinating to Sn(IV). Their in vitro cytotoxicity towards eight selected tumour cell lines has been evaluated by MTT (3-[4,5-Dimentylthiazole-2-yl]-2,5-diphenpyltetra-zolium bromide) method, and compounds 1 and 2 exhibit enhanced activity, such as 1 to SW480, 2 to HeLa, HepG2 and MCF-7, which exceeds matrine and cisplatin, and display synergistic contribution of their components. The cell cycle analyses show that compounds 1, 3 and MT exhibit cell cycle arrest at the G₂/M phase. Interactions of these compounds with calf thymus DNA (ct-DNA) have been investigated by spectroscopic analyses. The planar extension of the intercalative metal-matrine compounds increases the interaction of the metal-matrine with DNA, indicating that the cationic metal ions and configuration of the intercalated metal-matrine will affect the extent of interaction. Compound 2, [H-MT][AuCl₄], exhibits more intensive binding ability to DNA, which may correlate with intercalation and other action mode. The circular dichroism spectra of the ct-DNA bound with metal-MT compounds also suggest that ct-DNA interacted with 1, 2, 3 does not influence its secondary structure. Furthermore, both compounds 1 and 2 exhibit effective inhibition ability to topoisomerase (TOPO I) at concentration of 50 μM, while matrine and compound 3 do not.     

Substitution reactions of tetrahydrofuran in [Cr(thf)3Cl3] with mono and bidentate N-donor ligands: X-ray crystal structures of [Cr(bipy)(OH2)Cl3] and [HpyNH2][Cr(bipy)Cl4]

Substitution of thf ligands in [Cr(thf)₃Cl₃] and [Cr(thf)₂(OH₂)Cl₃] was investigated. 2,2′-Bipyridine (bipy) was reacted with [Cr(thf)₃Cl₃] to form [Cr(bipy)(thf)Cl₃] (1), which was subsequently reacted with water to give [Cr(bipy)(OH₂)Cl₃] (2). Reaction of 1 with acetonitrile (CH₃CN), pyridine (py) and pyridine derivatives to form [Cr(bipy)(L)Cl₃] (L = CH₃CN 3, py 4 and 4-pyR with R = NH₂5, Bu^t6 and Ph 7). In addition, the substitution of bipy in [Cr(thf)₃Cl₃] was followed by ¹H NMR spectroscopy at room temperature, which showed completion of the reaction in ca. 100 min. Complex 2 was characterised by single crystal X-ray diffraction. The theoretical powder diffraction pattern of 2 was compared to the experimentally obtained powder X-ray diffraction pattern, and shows excellent agreement. The dimer [Cr₂(bipy)₂Cl₄(μ-Cl)₂] was cleaved asymmetrically to give the anionic complex [Cr(bipy)Cl₄]⁻ (8) and [Cr(bipy)₂Cl₂]⁺ (9). Complexes 8 and 9 were characterised by single crystal X-ray diffraction.     

Syntheses and structures of heterobimetallic complexes derived from [Ga(edt)2] as a metalloligand (edt = SC2H4S): Potential precursors for ternary materials MGaS2 (M = Cu or Ag)

Metathesis reaction between equimolar amount of [Et₄N][GaCl₄] and Na₂edt in methanol resulted in the formation of the dichloro complex [Et₄N][Ga(edt)Cl₂] (1), whereas reaction of [Et₄N][GaCl₄] with two equivalents of Na₂edt in methanol gave the complex [Et₄N][Ga(edt)₂] (2) which can act as a metalloligand. Treatment of 2 with M(PPh₃)₂NO₃ in DMF/CH₂Cl₂ afforded the heterobimetallic complexes [Ga(edt)₂M-(PPh₃)₂] (M = Cu 3, Ag 4) in moderate yields. The structures of 1-4 were determined by single-crystal X-ray diffraction analyses. Both [Ga(edt)Cl₂]⁻ and [Ga(edt)₂]⁻ anions have a distorted tetrahedral geometry. The former consists of one five-membered ring formed by chelating dithiolate and two terminal chloride atoms while the latter consists of two five-membered rings formed by two the chelating dithiolates. Complexes 3 and 4 consist of metalloligand [Ga(edt)₂]⁻ anion chelated to [M(PPh₃)₂]⁺via the sulfur atoms. Both tetrahedrally coordinated Ga and Cu(Ag) atoms are bridged by two sulfur atoms, forming a planar “GaS₂M” (M = Cu, Ag) core. Thermogravimetry analysis revealed that heterobimetallic complexes 3 and 4 decomposed to give the corresponding ternary metal sulfide materials.     

Differential effects of Co(III), Ni(II), and Ru(III) amine complexes on Sindbis virus

Transition metal complexes [Co(cyclen)(NH₃)₂](ClO₄)₃⋅H₂O (cyclen = 1,4,7,10-tetraazacyclododecane) (2), [Co(NH₃)₅(OH₂)](CF₃SO₃)₃ (3) [Ni(NH₃)₆]Br₂ (4) and [Ru(NH₃)₆]Cl₃ (5) were tested against Sindbis infected baby hamster kidney (BHK) cells and show differential effects from the previously reported anti-viral complex [Co(NH₃)₆]Cl₃ (1). The macrocyclic complex 2 and labile aqua complex 3 show either no or little effect on the survival on Sindbis virus-infected cells as compared to that for 1, which show a monotonic increase in % BHK cell survival. Nickel and ruthenium ammine complexes 4 and 5 had a moderate influence of cell survival. While the results showed some anti-viral activity for some of the structural variations, it appears that 1, with its potential to be a broad-spectrum anti-viral compound, occupies a unique position in its ability to both significantly enhance cell survival and to decrease viral expression of infected cells. We also show that 1 also shows anti-viral activity against Adenovirus lending support to the broad-spectrum potential of this complex.     

New energetic materials: Synthesis and characterization of copper 5-nitriminotetrazolates

The energetic compounds 5-nitriminotetrazole (H₂AtNO₂, 1), 1-methyl-5-nitriminotetrazole (1MeHAtNO₂, 2) and 2-methyl-5-nitraminotetrazole (2MeHAtNO₂, 3), were reacted with Cu(NO₃)₂ · 3H₂O and CuCl₂ · 2H₂O, respectively, in water as well as in aqueous ammonia solution. The syntheses yielded the complexes [Cu(HAtNO₂)₂(H₂O)₄] (4), [Cu(AtNO₂)(NH₃)₃]₂ (5), (NH₄)₂[Cu(AtNO₂)₂(H₂O)₂] (6), [Cu(1MeAtNO₂)₂(NH₃)₂] (7), [Cu(2-MeAtNO₂)₂(2-MeHAtNO₂)₂] (8), [Cu(2MeAtNO₂)₂]_∞ (9), [Cu(2-MeAtNO₂)₂(NH₃)₂] (10), and [Cu(2MeAtNO₂)₂(NH₃)₄] · H₂O (11). All complexes were characterized using low temperature single crystal X-ray diffraction, IR spectroscopy, elemental analysis, and differential scanning calorimetry. The magnetic properties of six of the complexes were investigated. Due to the energetic characters, the sensitivities towards impact and friction were investigated using the BAM drophammer and friction tester. The values range from “very sensitive”, comparable to primary explosives, to “insensitive” depending on the amount of water or ammonia coordinated. Since Cu(II) salts can be used for colorants in pyrotechnics, the combustions and flame colors were discovered to be intensively green.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Out-of-plane dimeric Mn quadridentate Schiff-base complexes: Synthesis, structure and magnetic properties

Four Mn^III quadridentate Schiff-base compounds have been prepared and structurally characterized: [Mn(salpn)(CH₃OH)₂]BPh₄ (1), [Mn₂(salpn)₂(N₃)₂] (2), [Mn₂(salpn)₂(NCS)₂] (3), [Mn₂(salpn)₂(H₂O)₂](H₂O)(ClO₄)₂ (4) (salpn = N,N′-(1,2-propylene)-bis-(salicylideneiminate)). Among them, 1 is a discrete Mn^III monomeric complex with a square-bipyramidal geometry. Complexes 2, 3 and 4 form the similar phenolate-bridged out-of-plane dimers. Magnetic susceptibility studies reveal that 2, 3 and 4 all exhibit ferromagnetic intra-dimer coupling between Mn^III ions.     

The syntheses, characterizations, X-ray crystal structures and properties of Cu(I) complexes of a bis-bidentate schiff base ligand

Bis-bidentate Schiff base ligand L and its two mononuclear complexes [CuL(CH₃CN)₂]ClO₄ (1) and [CuL(PPh₃)₂]ClO₄ (2) have been prepared and thoroughly characterized by elemental analyses, IR, UV-Vis, NMR spectroscopy and X-ray diffraction analysis. In both the complexes the metal ion auxiliaries adopt tetrahedral coordination environment. Their reactivity, electrochemical and photophysical behavior have been studied. Complex 1 shows reversible Cu^II/I couple with potential 0.74 V versus Ag/AgCl in CH₂Cl₂. At room temperature L is weakly fluorescent in CH₂Cl₂, however in Cu(I) complexes 1 and 2 the emission in quenched.     

Functional phosphines. Part XIV. Cationic (P,N)2-coordinated hydrides of iridium(III): catalysts for CO hydrogenation or transfer hydrogenation?

Treatment of trans-[IrCl(CO)(PPh₃)₂] with Ph₂PCH₂CH₂NH₂ in refluxing para-xylene gave (OC-6-43)-[Ir(H)(Cl)(Ph₂PCH₂CH₂NH₂)₂]Cl (1) which interacted with K[BH(s-Bu₃)] to produce a mixture of (OC-6-22)-[IrH₂(Ph₂PCH₂CH₂NH₂)₂]Cl (2a) and (OC-6-32)-[Ir(H)(Cl)(Ph₂PCH₂CH₂NH₂)₂]Cl (2b). The trans-dihydride 2a was isolated in pure form from the reaction between 1 and KOH/i-PrOH. Different from its isoelectronic (P,N)₂-coordinated Ru^II analogues, the cationic chloro hydrido complex 1 does not act as a catalyst for the direct hydrogenation of acetophenone by molecular H₂, if activated by strong alkoxide base, but rather catalyzes the transfer hydrogenation of the CO bond with methanol or isopropanol as proton/hydride sources. Dihydrido complex 2a is ascribed the role of the actual catalyst as it supports the transfer hydrogenation reaction even in the absence of base. The crystal structure of the addition compound 1 · 2EtOH has been determined.     

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.     

Synthesis and characterisation of dinuclear oxomolybdenum(V) complexes with thienyl carboxylate ligands

The first structurally characterised oxomolybdenum(V) complexes with thienyl carboxylate ligands were prepared by the reaction of [Mo₂O₃(C₅H₇O₂)₄] or (NH₄)₂[MoOCl₅] with the corresponding acid (2-thiophenecarboxylic, 5-methyl-2-thiophenecarboxylic or 3-(3-thienyl)acrylic acid). Complexes [Mo₂O₃(μ-OC₂H₅)(μ-O₂CR)(C₅H₇O₂)₂](R = -C₄H₃S (1), -C₄H₂S(CH₃) (2) or -CHCHC₄H₃S (3)) were obtained upon substitution of two acetylacetonate ligands from [Mo₂O₃(C₅H₇O₂)₄] with RCOO⁻ in dry ethanol. Reactions of (NH₄)₂[MoOCl₅] with the corresponding thienyl carboxylic acid in the presence of γ-picoline (C₆H₇N) yielded complexes (C₆H₇NH)[Mo₂O₄(μ-O₂CR)Cl₂(C₆H₇N)₂] (R = -C₄H₃S (4), -C₄H₂S(CH₃) (5) or -CHCHC₄H₃S (6)). All of the six new complexes were characterised as dinuclear. The molecular structures of 1, 3, 4·0.5CH₃CN and 5 were determined by the single crystal X-ray diffraction method. In the complexes the two molybdenum atoms are doubly bridged either by one oxygen and one ethoxy-oxygen, or alternatively by two oxo-oxygens, and are additionally bridged by the thienyl carboxylate ion in a didentate bridging manner. All complexes were further characterised by means of chemical analysis, IR spectroscopy, TG and in some cases by the one and two-dimensional NMR method.     

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.     

Structural variations and spectroscopic properties of copper(I) complexes with bis(schiff base) ligands

Six copper(I) complexes {[Cu₂(L1)(PPh₃)₂I₂] · 2CH₂Cl₂}_n (1), {[Cu₂(L2)(PPh₃)₂]BF₄}_n (2), [Cu₂(L3)(PPh₃)₄I₂] · 2CH₂Cl₂ (3), [Cu₂(L4)(PPh₃)₄I₂] (4), [Cu₂(L5)(PPh₃)₂I₂] (5) and [Cu₂(L6)(PPh₃)₂I₂] (6) have been prepared by reactions of bis(schiff base) ligands: pyridine-4-carbaldehyde azine (L1), 1,2-bis(4′-pyridylmethyleneamino)ethane (L2), pyridine-3-carbaldehyde azine (L3), 1,2-bis(3′-pyridylmethyleneamino)ethane (L4), pyridine-2-carbaldehyde azine (L5), 1,2-bis(2′-pyridylmethyleneamino)ethane (L6) with PPh₃ and copper(I) salt, respectively. Ligand L1 or L2 links (PPh₃)₂Cu₂(μ-I)₂ units to form an infinite coordination polymer chain. Ligand 3 or 4 acts as a monodentate ligand to coordinate two copper(I) atoms yielding a dimer. Ligand 5 or 6 chelates two copper(I) atoms using pyridyl nitrogen and imine nitrogen to form a dimer. Complexes 1-4 exhibit photoluminescence in the solid state at room temperature. The emission has been attributed to be intraligand π-π* transition mixed with MLCT characters.     

Hydrothermal synthesis of copper complexes of 4′-pyridyl terpyridine: From discrete monomer to zigzag chain polymer

Seven copper complexes [Cu(L1)I₂] (1), [Cu₂(L1)₂I₂]₂[Cu₂(μ-I)₂I₂] (2), [Cu(L2)I₂] (3), [Cu₂(L2)(μ-I)I(PPh₃)] (4), [Cu₄(L2)₂(μ-I)₂I₂] (5), {[Cu(L2)I]₂[Cu₂(μ-I)₂I₂]}_n (6) and [Cu₂(L2)(μ-I)₂]_n (7) have been prepared by reactions of ligands: 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine (L1) and 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine (L2) with CuI in hydrothermal conditions, respectively. By alternating the oxidations states of the metal centers, increasing stoichiometric metal/ligand ratio and introducing a second ligand, the compounds, were successfully developed from mononuclear (1 and 3) to multinuclear (2, 4 and 5) and polymers (6 and 7). The synthesis of these compounds may provide an approach for the construction of coordination compounds of 4′-pyridyl terpyridine with different nuclearity.     

Four new copper(II) complexes with di-substituted s-triazine-based ligands

In this paper, two di-substituted triazine-based ligands, 6-chloro-N,N,N′N′-tetrakis-pyridin-2-ylmethyl-[1,3,5]triazine-2,4-diamine (L1), and 6-chloro-N,N′-bis-pyridin-2-ylmethyl-N,N′-bis-thiophen-2-ylmethyl-[1,3,5]triazine-2,4-diamine (L2), have been prepared. Reaction of CuCl₂·2H₂O and Cu(NO₃)₂·3H₂O with L1 and L2 results in the formation of [Cu₂Cl₄(L1)]·3MeOH (compound 1), [Cu₄(NO₃)₈(L1)₂]·2.07CH₂Cl₂·0.93MeOH (compound 2), [Cu₂Cl₄(L2)₂] (compound 3) and [Cu(NO₃)₂(L2)]·CH₂Cl₂ (compound 4), respectively, which have been fully characterized and determined by single-crystal X-ray crystallography, FT-IR, elemental analysis, thermogravimetric measurement and magnetic susceptibility. The dinuclear compound 1 shows strong π-π interactions between the neighboring pyridine rings. The nitrate-π (1,3,5-triazine ring) interaction with the distance of 2.755 Å in compound 2, is the closest contact reported so far. Compounds 3 and 4 are mononuclear copper(II) compounds, in which none of thiophene rings coordinates with copper(II) ion. In addition, the different orientations of two thiophene rings in compounds 3 and 4 lead to the π-π and CH₂Cl₂-π (thiophene ring) interactions in compound 4, but not in compound 3.