Cationic Dinuclear Complexes Research Articles

Antifungal and antibacterial activity of two new Ni(II) complexes of a pyrazole-appended thiophene containing bidentate schiff-base ligand: Synthesis, spectroscopy and crystal structures

A new pyrazole-appended thiophene containing Schiff-base ligand, N-(thiophene-2-ylmethyl)-1-(5-methyl-1H-pyrazol-3-yl)methanimine, (MPATA) (1) and its two new di- and mononuclear Ni(II) complexes, [Ni2(MPATA)4 (µ-Cl)2]Cl2 (2) and [Ni(MPATA)3](ClO4)2 (3), respectively, are reported. All the synthesized compounds have been thoroughly characterized by several physico-chemical and spectroscopic studies. Single crystal X-ray diffraction studies have identified 2 as a chloro‑bridged di-nuclear cationic complex, while 3 as a mononuclear distorted octahedral one. In 2, coordination to each metal centre has been occurred by two molecules of ‘NN’ bidentate MPATA and each Ni(II) centre assumes a distorted octahedral geometry. On the other hand, in 3, three molecules of the ‘NN’ bidentate MPATA coordinate to the Ni(II) centre. Both the complexes 2 and 3 exhibit significant hydrogen bonding and intramolecular π···π stacking interactions. All the three compounds have been found to display significant antifungal activity against plant pathogen funguses Colletotrichum siamense (CS) and Fusarium equisetum (F.E) and antibacterial activity against gram-positive and gram-negative bacteria, but no such effects have been found against human pathogen fungus Candida albicans sc5314.

Syntheses, characterizations and crystal structures of two Ni(II) complexes [Ni2(neoc)4(H2O)(CO3)](NO3)2·3H2O and [Ni(bapa)2](NO3)2·H2O and magnetic properties of the carbonato complex

By the reaction of nickel(II) nitrate hexahydrate with 2,9-dimethyl-1,10-phenanthroline (neoc) and bis(3-aminopropyl)amine (bapa) two novel complexes were isolated, namely [Ni2(neoc)4(H2O)(CO3)](NO3)2·3H2O (1) and [Ni(bapa)2](NO3)2·H2O (2). Both structures are ionic and comprise hexacoordinated Ni(II) central atoms. Complex 1 is built up of dinuclear [Ni2(neoc)4(H2O)(CO3)]2+ complex cation, nitrate anions and water solvate molecules. The dinuclear complex cation is centrosymmetric and the two Ni(II) atoms are linked by a μ3-bridging-chelating carbonato ligand which, due to the presence of an inversion centre, exhibits two orientations with equal probability. The coordination sphere of Ni(II) atom is heteroleptic with an N4O2 donor set formed by two chelating neoc ligands and two O-donor atoms from bridging carbonato and aqua ligands. The carbonato ligand was formed by transformation of absorbed carbon dioxide from air (single crystals) or from dry ice (bulk sample). The crystal structure of 2 is formed by [Ni(bapa)2]2+ complex cation, nitrate anions and water solvate molecule. The coordination sphere of Ni(II) atom in 2 is homoleptic with N6 donor set. Both bapa ligands act as double chelating 3 N-donor ligands and are coordinated in mer-fashion. The study of the magnetic response of 1 in the temperature range 1.8–300 K revealed that the system can be considered as a system of antiferromagnetic S = 1 spin dimers with exchange interaction J/hc = -13.86 cm−1 (J/kB = -19.96 K) and axial single-ion anisotropy D/hc = -4.94 cm−1 (D/kB = -7.12 K). The experimental magnetic results were corroborated by ab initio and DFT calculations.

Cationic dinuclear complexes [M2(PCP)2μ-Cl][GaCl4] of the group 10 elements. metallophilic interactions and catalytic dehydrogenation of Me2NHBH3.

The facile synthesis of the cationic dinuclear group 10 complexes [M2(PCP)2μ-Cl]+ (M = Ni, Pd, Pt) by transmetallation from a simple Ga precursor is reported (PCP = 2,6-(Ph2P)C6H3). Their use for the catalysed dehydrogenation of Me2NHBH3 shows that Ni has a higher reactivity than Pt, whereas Pd is inactive.

Piano‐stool dinuclear ruthenium (II) complexes of pyrazine‐carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

Reactions of ligand pyrazine‐2‐carboxylic acid (HL1) with [Ru(η6‐p‐cymene)Cl2]2precursor gave the dinuclear piano‐stool ruthenium (II) complex [{Ru(η6‐p‐cymene)Cl2}‐μ‐(L1)‐{Ru(p‐cymene)Cl}] (Ru1). Separately, reactions ofN‐(quinolin‐8‐yl) pyrazine‐2‐carboxamide (HL2), 5‐methyl‐N‐(−(quinolin‐8‐yl) pyridine‐2‐carboxamide (HL3) and 5‐chloro‐N‐(quinolin‐8‐yl) pyridine‐2‐carboxamide (HL4) with [Ru(η6‐p‐cymene)Cl2]2dimer in the presence of KPF6afforded the cationic dinuclear complexes [{Ru(η6‐p‐cymene)Cl}2‐μ‐(L2)][PF6] (Ru2), [{Ru(η6‐p‐cymene)Cl}2‐μ‐(L3)][Ru(L3)Cl3] (Ru3) and [{Ru(η6‐p‐cymene)Cl}2‐μ‐(L4)][PF6] (Ru4). The Ru (II) complexes were analysed using FT‐IR,1H,13C{1H},31P{1H} (Ru2andRu4) and19F (Ru2andRu4) NMR spectroscopic techniques, micro‐analyses and mass spectrometry. Molecular structures of complexesRu1andRu3were confirmed to display piano‐stool coordination nature using single‐crystal X‐ray crystallography analyses. All the complexes (Ru1–Ru4) mediated the transfer hydrogenation (TH) of a broad spectrum of ketones in isopropanol in the presence of a base and demonstrated high catalytic activities (TON of 24,000) at catalyst concentrations of 0.002 mol%. In general, the catalytic performance of these Ru (II) complexes depended on the identity of the ligands, coordination chemistry and ketone substrates.

Oxidation of thymol catalysed by a water-soluble Cu(II)-adipate-diphenylamine complex in a biphasic medium

A metal–organic framework involving a dicarboxylate (adipic acid) and dipyridylamine (dpya), [Cu2(dpya)(µ-adipate)].2ClO4·2H2O, has been synthesized by one-pot reaction and structurally characterized by X-ray diffraction. Pentacoordinated Cu(II) dimer complex links the adjacent Cu(dpya) units through chelating carboxylate oxygens of adipate dianion in a coordination pattern with the metal center. The centrosymmetric adipate-bridged dinuclear complex cations [Cu2(dpya)(µ-adipate)]2+ are assembled into pseudo-2D supramolecular networks through aromatic stacking interactions (4.108 Å) and also hydrogen bondings with counter ion with the coordinated water molecule. The catalytic performance of the compound was investigated for thymol (T) oxidation in organic solvents and water/hexane biphasic systems. Its selectivity was measured as 100 % for T to thymoquinone (TQ). A novel, simple, and efficient catalyst system (TOF = 400 h−1) was developed for the oxidation of T into a valuable derivate, TQ, using TBHP with subs./cat.(100) in a water/hexane biphasic system at 70 οC.

Dinuclear silver(I) and gold(I) complexes with chiral oxazoline‐NHC ligands

The coordination chemistry of chiral NHC-oxazoline bidentate ligands was investigated with silver(I) and gold(I), yielding stable dinuclear cationic complexes in good yields via N-coordination of the oxazoline heterocycle. After full characterization of these complexes, the reactivity in homogeneous catalysis and under oxidative conditions was studied.

Ferro- vs. antiferromagnetic exchange between two Ni(II) ions in a series of Schiff base heterometallic complexes: what makes the difference?

Three new NiII/ZnII heterometallics, [NiZnL'2(OMe)Cl]2 (1), [NiZnL''(Dea)Cl]2·2DMF (2) and [Ni2(H3L''')2(o-Van)(MeOH)2]Cl·[ZnCl2(H4L''')(MeOH)]·2MeOH (3), containing three-dentate Schiff bases as well as methanol or diethanolamine (H2Dea) or o-vanillin (o-VanH), all deprotonated, as bridging ligands were synthesized and structurally characterized. The Schiff base ligands were produced in situ from o-VanH and CH3NH2 (HL'), or NH2OH (HL"), or 2-amino-2-hydroxymethyl-propane-1,3-diol (H4L'''); a zerovalent metal (Ni and Zn in 1, Zn only in 2 and 3) was employed as a source of metal ions. The first two complexes are dimers with a Ni2Zn2O6 central core, while the third compound is a novel heterometallic cocrystal salt solvate built of a neutral zwitterionic ZnII Schiff base complex and of ionic salt containing dinuclear NiII complex cations. The crystal structures contain either centrosymmetric (1 and 2) or non-symmetric di-nickel fragment (3) with NiNi distances in the range 3.146-3.33 Å. The exchange coupling is antiferromagnetic for 1, J = 7.7 cm-1, and ferromagnetic for 2, J = -6.5 cm-1 (using the exchange Hamiltonian in a form Ĥ = Jŝ1ŝ2). The exchange interactions in 1 and 2 are comparable to the zero-field splitting (ZFS). High-field EPR revealed moderate magnetic anisotropy of opposite signs: D = 2.27 cm-1, E = 0.243 cm-1 (1) and D = -4.491 cm-1, E = -0.684 cm-1 (2). Compound 3 stands alone with very weak ferromagnetism (J = -0.6 cm-1) and much stronger magnetic anisotropy with D = -11.398 cm-1 and E = -1.151 cm-1. Attempts to calculate theoretically the exchange coupling (using the DFT "broken symmetry" method) and ZFS parameters (with the ab initio CASSCF method) were successful in predicting the trends of J and D among the three complexes, while the quantitative results were less good for 1 and 3.

Iron(III) and cyano-bridged dinuclear copper(II) complexes: synthesis, structures and magnetic property of the copper(II) complex

This report describes the synthesis and structural characterizations of three new complexes; [Na3Fe2(bbp)(Hbbp)(CN)6(H2O)9]·4H2O (1), (Bu4N)[Fe(bbp)2]·3CH3OH·2H2O (2), and a cyano-bridged dinuclear copper(II) complex, [Cu2(tren)2(CN)][Fe(bbp)2]3· 6CH3OH·4H2O (3), where H2bbp = bis(2-benzimidazolyl)pyridine and tren = tris(2-aminoethyl)amine. X-ray crystallography reveals that the geometry of iron(III) centers in the complex anions of 1–3 is an octahedral, while it is a trigonal bipyramidal around copper(II) center in the complex cation of 3. Both bbp ligands meridionally coordinate iron(III) centers in the complex cations of 2 and 3, while three cyanide ions and bbp (or Hbbp) ligand occupied either of the meridional positions around the metal center in 1. In the dinuclear complex cation of 3, the Cu(II)-CN-Cu(II) bridging region is strictly linear as dictated by the symmetry with Cu···Cu separation of 5.084 (7) A. Variable temperature magnetic susceptibility study shows that the cyano-bridge mediates the antiferromagnetic coupling between copper(II) centers with J value of −110 K in 3. Two Fe(III) complexes and one heterobimetallic Fe(III)–Cu(II) complex have been synthesized and X-ray crystallographically characterized. Variable temperature magnetic susceptibility study revealed the antiferromagnetic coupling between the Cu(II) centers in Fe(III)–Cu(II) complex. The magneto-structural correlation has been further established.

BODIPY-based Ru(II) and Ir(III) organometallic complexes of avobenzone, a sunscreen material: Potent anticancer agents

The use of organic compounds with known medicinal properties in the synthesis of metal-based complexes is an important alternative to improve the biological activity of metal-based drugs. The reaction of [M(arene)Cl2]2 (M = Ru, arene = p-cymene and M = Ir, arene = pentamethylcyclopentadienyl, cp*) with avobenzone (1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione, AVBH) and KOH in methanol leads to the formation of the neutral complexes [Ru(p-cymene)(AVB)Cl] 1 and [Ir(cp*)(AVB)Cl] 2 (cp* = pentamethylcyclopentadienyl). Subsequent reaction of 1 and 2 with pyridyl derivative-BODIPY ligands, BDP and BDPCC (BODIPY = boron dipyrromethene, BDP = 4-dipyridine boron dipyrromethene, BDPCC = 4-ethynylpyridine boron dipyrromethene) in methanol gives a series of four new dicationic supramolecules: [Ru2(p-cymene)2(AVB)2BDP][2CF3SO3] 3, [Ir2(cp*)2(AVB)2BDP][2CF3SO3] 4, [Ru2(p-cymene)2(AVB)2BDPCC][2CF3SO3] 5 and [Ir2(cp*)2(AVB)2BDPCC][2CF3SO3] 6. The synthesized complexes are fully characterized using multiple analytical techniques, including elemental analysis, 1H NMR, 13C NMR, 19F NMR (NMR = Nuclear Magnetic Resonance), Infrared Radiation (IR), Electrospray Ionization-Mass Spectrometry (ESI-MS), Ultraviolet-visible (UV–Vis) and fluorescence spectroscopy. The structures of these complexes are further rationalized using density functional theory (DFT) calculations. The antiproliferative activity of the neutral and dinuclear cationic complexes is evaluated in vitro in different human cancer cell lines. These complexes are found to be active against different cancer cell lines with half maximal inhibitory concentration (IC50) values between 1 and 5 μM. Complexes 5 and 6 displayed the lowest IC50 values in all the cell lines studied. The activity of 5 and 6 is comparable to that of the well-known chemotherapy drug doxorubicin. Detailed biophysical studies indicate that complexes 5 and 6 exhibit very good Deoxyribonucleic acid (DNA) binding properties, causing the unwinding of the double helix, which is a probable reason for their high cytotoxicity.

Syntheses, characterization and reactivity of dinuclear ruthenium-nickel complexes with hexane-2,5-dione bis(thiosemicarbazonato) ligands

Treatment of hexane-2,5-dione bis(thiosemicarbazones) ([CH3‒C{= N‒NH‒C(=S)‒NHR}‒CH2]2, R = H, L1H2; CH3, L2H2‒Me; CH2CH3, L3H2‒Et; C6H5, L4H2‒Ph) with nickel(II) acetate hydrate in refluxing ethanol gave a series of NiIIN2S2 metalloligands [Ni(L-R)] for the generation of hetero-bimetallic complexes. The reaction of equal mole each of [Ni(L1)], [Ni(L2‒Me)], [Ni(L3‒Et)], or [Ni(L4‒Ph)] with [RuCl2(dmso)4] (dmso = dimethyl sulfoxide) at reflux resulted in isolation of neutral dinuclear ruthenium-nickel complexes [RuCl2{(Ni(L1)}(dmso)2] (1), [RuCl2{(Ni(L2‒Me)}(dmso)2] (2), [RuCl2{(Ni(L3‒Et)}(dmso)2] (3), and [RuCl2{(Ni(L4‒Ph)}(dmso)2] (4). Interaction of [Ni(L-R)] with [CpRu(PPh3)2Cl] (Cp‒ = cyclopentadienyl) at room temperature led to formation of cationic dinuclear organoruthenium-nickel complexes [CpRu{(Ni(L1)}(PPh3)]Cl (5), [CpRu{(Ni(L2‒Me)}(PPh3)]Cl (6), [CpRu{(Ni(L3‒Et}(PPh3)]Cl (7), and [CpRu{(Ni(L4‒Ph}(PPh3)]Cl (8). New bimetallic ruthenium-nickel complexes 1–8 have been characterized spectroscopically, of which molecular structures of three complexes [RuCl2{(Ni(L2‒Me)}(dmso)2]·CH2Cl2 (2·CH2Cl2), [CpRu{(Ni(L2‒Me)}(PPh3)]Cl⋅EtOH (6⋅EtOH), and [CpRu{(Ni(L3‒Et}(PPh3)]Cl (7⋅H2O) have been established by single-crystal X-ray crystallography. Their catalytic activities for the acetalation of benzaldehyde in the presence of molecular H2 have been also investigated in this paper.

Atom Transfer Radical Addition Catalyzed by Ruthenium–Arene Complexes Bearing a Hybrid Phosphine–Diene Ligand

The synthesis and characterization of a series of arene ruthenium complexes bearing either (3,5-cycloheptadienyl)diphenylphosphine or (cycloheptyl)diphenylphosphine are reported. Upon irradiation or heating, all these complexes lose their arene ligand but then exhibit a different behavior depending on the nature of the phosphine ligand. (Cycloheptadienyl)phosphine complexes 1 and 3 give a cationic dinuclear Ru complex 5 for which the two Ru atoms are bridged by three chlorido ligands and flanked by two tridendate (cycloheptadienyl)phosphines. (Cycloheptyl)diphenylphosphine complexes 2 and 4 undergo arene exchange when toluene is used as solvent or degrade in dichloromethane. ATRA catalytic trials conducted in parallel with these complexes using CCl4 and styrene as standard substrates, highlighted the deep impact of the dienyl moiety on the results. Under smooth conditions (UV irradiation or moderate heating), only (cycloheptyl)phosphine derivatives give Karasch adduct in satisfactory yields. Their perform...

Assembly, structures, electrocatalytic and photocatalytic properties of a series of Anderson-type polyoxometalate-based metal–organic complexes based on flexible pyridyl-amide ligands

Five new Anderson-type polyoxometalate-based metal–organic complexes, [Cu4(μ3-OH)2(H2O)6(4-dpye)2(TeMo6O24)]·2H2O (1), [Cu(4-dpyb)(CrMo6(OH)6O18)2(H2O)2][Cu(4-dpyb)(H2O)4](4-H2dpyb)·6H2O (2), H[Cu2(3-dpyb)2(C2O4)(CrMo6(OH)6O18)]·8H2O (3), [Cu2(4-dpyh)(CrMo6(OH)5O19)(H2O)8]·10H2O (4) and [Cu4(μ2-OH)(μ3-OH)(H2O)6(4-dpyh)(TeMo6O24)]·H2O (5) (4-dpye=N,N′-bis(4-pyridinecarboxamide)-1,2-ethane, 4-dpyb=N,N′-bis(4-pyridinecarboxamide)-1,4-butane, 3-dpyb=N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyh=N,N′-bis(4-pyridinecarboxamide)-1,6-hexane), were hydrothermally prepared and structurally characterized by single crystal X-ray diffraction analyses and characterized by single-crystal X-ray diffraction, elemental analysis, IR, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA). Complex 1 is a 2D network, which is constructed from Cu4–TeMo6 inorganic chains and 4-dpye ligands. Complex 2 contains two types of 1D chains. Complex 3 shows a 1D ring-like chain structure, in which the CrMo6 anions act as fourfold monodentate ligands consolidating the [Cu2(3-dpyb)2(C2O4)] rings. Complex 4 is a 0D structure containing a dinuclear complex cation [Cu2(4-dpyh)]4+ and discrete CrMo6 anion. Complex 5 exhibits a 3D framework constructed from 2D Cu4–TeMo6 inorganic layer and 4-dpyh ligands. The spacer lengths and N-donor sites of the bis-pyridyl-bis-amide ligands, as well as different polyoxometalates play important roles in tuning the structures of the title complexes. The electrochemical behavior and electrocatalytic properties, as well as the photocatalytic activities of the title complexes have been studied.

Synthesis and Crystal Structure of a 4,4’-bipyridine Linked Dinuclear Copper(II) Complex Derived from 2-{[2-(2-hydroxyethylamino)ethylimino] methyl}-6-methylphenol

A novel 4,4'-bipyridine linked dinuclear copper(II) complex, [Cu2L2(bipy)](NO3)2·bipy (L = 2-[2-(2-hydroxyethylamino) ethylimino]methyl-6-methylphenol; bipy = 4,4'-bipyridine), was prepared and characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction. The Cu···Cu distance is 11.129(2) Å. The CuII atom is coordinated by one phenolate O, one imine N, and one amine N atoms of a Schiff base ligand, and one N atom of the bridging 4,4'-bipyridine ligand, forming a square planar geometry. In the crystal structure of the complex, the dinuclear copper complex cations are linked by 4,4'-bipyridine molecules through intermolecular O-H···N hydrogen bonds, to form 1D chains running in the [2 0 -1] direction.

Crystal structure of μ-4-oxidobenzoato-κ2O1:O4-bis-[bis-(1,10-phenanthroline-κ2N,N')copper(II)] bis-(4-hy-droxy-benzoate) 7.5-hydrate.

The title hydrated complex, [Cu2(C7H4O3)(C12H8N2)4](C7H5O3)2·7.5H2O, is composed of dinuclear CuII complex cations, noncoordinating 4-hy-droxy-benzoate anions and water mol-ecules of crystallization. In the dinuclear complex cation, the CuII ions are bridged by a 4-oxidobenzoate ligand and thus each metal ion is five-coordinated by two chelating 1,10-phenanthroline (phen) mol-ecules and one anionic O atom in a distorted trigonal-bipyramid geometry. In the crystal, aromatic π-π stacking occurs between phen rings of neighbouring dinuclear CuII complex cations, forming two-dimensional supra-molecular systems parallel to (100).

Novel cationic dinuclear η3-methallylpalladium complexes containing N,N′-donor bridging ligands: Synthesis, characterization and crystal structure

A series of bifunctional ligands of the type, 1,4-{(2-C5H4N)RC = N}2-C6H4 [R = H (L1), Me (L2)], 1,4-{(2-C5H4N)HCN}2-(C6H4)2 [L3] and 1,4-{(2-C5H4N)HCN}2-C2H4 [L4] were synthesized and fully characterized by IR, 1H NMR and 13C NMR spectroscopy. These ligands react with Pd(dba)2 in the presence of the salt methallyloxytris(dimethylamino)phosphonium hexafluorophosphate [C4H7OP(NMe2)3]+PF6− to give the novel cationic dinuclear η3-methallylpalladium complexes C1C4 in high yields. All new complexes C1C4 have been characterized by CHN analyses, 1H, 13C, 31P NMR and IR spectroscopy. The X-ray crystal structure of complex C1 has been determined.

Synthesis, crystal structure, and antimicrobial activity of a novel chlorido-bridged dinuclear manganese(III) complex derived from N,N′-bis(5-methylsalicylidene)diethylenetriamine

ABSTRACTA novel chlorido-bridged dinuclear manganese(III) complex, [Mn2L2(μ-Cl)Cl2)]·Cl·0.5CH3OH, where L is the zwitterionic form of N,N’-bis(5-methylsalicylidene)diethylenetriamine, has been prepared and characterized by elemental analyses, IR, and single-crystal X-ray crystallographic determination. The crystal of the complex is monoclinic: space group C2/c, a = 20.0300(9), b = 22.8494(8), c = 22.127(1) Å, β = 112.882(3)°, V = 9330.0(7) Å3, Z = 8. The asymmetric unit of the compound contains two dinuclear manganese complex cations, two chloride anions, and one methanol solvate. The Schiff base ligand coordinates to two Mn atoms through the phenolate O and imine N atoms, with the amine N atom protonated. The effect of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans was studied.

Mono- and dinuclear vanadium complexes with the pentadentate schiff base 2,6-diacetylpyridine bis(nicotinylhydrazone): Synthesis and structures

A reaction between VOSO4, 2,6-diacetylpyridine, and nicotinohydrazide in a molar ratio of 1: 1: 2 afforded two complexes differing in both color and crystal shape as well as in chemical composition and molecular structure. The compositions and structures of the vanadium complexes were determined by IR spectroscopy and X-ray diffraction (CIF files CCDCnos. 1411235 (I) and 1411236 (II)). These complexes can be formulated as [V2II(H2L)2](NO3)4 ∙ H2O (I) and [VIV(=O)(H2L)(SO4)] ∙ 5H2O (II), where H2L is 2,6-diacetylpyridine bis(nicotinylhydrazone). Complex I consists of centrosymmetric dinuclear complex cations [V2(H2L)2]4+, NO3- anions, and crystal water molecules in a ratio of 1: 4: 1; complex II is built from molecular V(IV) complexes and crystal water molecules in a ratio of 1: 5. The coordination polyhedron of the metal atom in I is a tetragonal pyramid made up of the electron-donating atoms N3O2 of two ligands H2L. The coordination polyhedron of the metal atom in II is a pentagonal bipyramid made up of the electron-donating atoms N3O2 of one neutral five-coordinate ligand H2L and two O atoms coming from the oxo ligand and the SO42- anion coordinated in a monodentate fashion.

Interesting copper(ii)-assisted transformations of 2-acetylpyridine and 2-benzoylpyridine.

The reactions of various copper(ii) sources with 2-acetylpyridine, (py)(me)CO, and 2-benzoylpyridine, (py)(ph)CO, under strongly basic conditions have been studied and novel ligand transformations have been discovered. Reaction of Cu(ClO4)2·6H2O and (py)(me)CO in the presence of NBu4(n)OMe (1 : 1 : 1) in CHCl3 gave a mixture of [Cu2Cl2(HLA)2](ClO4)2 (1) and [Cu2Cl2(LB)2(ClO4)2] (2), where HLA is 3-hydroxy-1,3-di(pyridin-2-yl)-butane-1-one and LB is the zwitterionic-type ligand 3-hydroxy-1-methyl-3-(pyridin-2-yl)-3H-indolizin-4-ium. The ligand HLA is formed through an aldol reaction-type mechanism, while the formation of LB takes place via an intramolecular nucleophilic attack of the remote 2-pyridyl nitrogen atom on the positive carbonyl carbon of HLA, after the transformation of the latter through deprotonation and dehydration. The Cu(II) ions in 1 are bridged by two 2.1111 HLA ligands resulting in a long Cu(II)Cu(II) distance (5.338 Å); the metal ions in 2 are triply bridged by the alkoxide oxygen atoms of the two 2.21 LB ligands and one 2.1100 perchlorato group. The absence of α-hydrogens in (py)(ph)CO leads the reactivity of this ligand in the presence of Cu(II) to different pathways. The Cu(ClO4)2·6H2O/(py)(ph)CO/NBu4(n)OMe reaction mixture in MeOH/H2O (25 : 1 v/v) gave the dinuclear cationic complex [Cu2{(py)(ph)CO}2(LC)2](ClO4)2 (3), where LC(-) is the anion of (methoxy)(phenyl)(pyridin-2-yl)methanol formed in situ via the nucleophilic addition of MeO(-) to the carbonyl carbon of (py)(ph)CO upon Cu(II) coordination. The Cu(II) ions in the cation are doubly bridged by the deprotonated oxygen atoms of the two LC(-) ligands. Replacement of Cu(ClO4)2·6H2O with Cu(NO3)2·3H2O and NBu4(n)OMe with NMe4OH and the decrease of the H2O concentration in the above reaction system yielded the tetranuclear coordination cluster [Cu4(OMe)2(NO3)4{(py)(ph)CO}2(LC)2] (4). The Cu(II) centres in this complex define a parallelogram. Two parallel sides of the parallelogram are each supported by deprotonated oxygen atoms belonging to a 2.21 LC(-) ligand and a 2.2 MeO(-) group. The metal ions that define each of the other two sides are singly bridged by an oxygen atom of a 2.210 nitrato group. No bridging exists between the Cu(II) ions that define the two diagonals of the parallelogram. Replacement of MeOH with EtOH in the reaction system that gave 4 resulted in the dinuclear complex [Cu2(NO3)2(LD)2)(EtOH)] (5), LD(-) being the anion of (ethoxy)(phenyl)(pyridin-2-yl)methanol. The Cu(II) ions are doubly bridged by the alkoxide oxygen atoms of the two 2.21 LD(-) ligands. The 1 : 1 : 1 Cu(NO3)2·3H2O/(py)(ph)CO/NMe4OH reaction system in CH3NO2 gave the dinuclear complex [Cu2(NO3)2(LE)2] (6), where LE(-) is the anion of 2-nitro-1-phenyl-1-(pyridin-2-yl)ethanol. The OH(-) ion abstracts one of the methyl hydrogens of CH3NO2, and once the carbanion (-):CH2NO2 is formed it attacks the positive (δ+) carbonyl carbon of (py)(ph)CO; as the carbanion forms the new C-C bond, the π electrons of the carbonyl group of the original ligand are transferred completely to oxygen forming the alkoxide-type ligand LE(-). The Cu(II) ions are doubly bridged by the alkoxide oxygen atoms of the two 2.21 LE(-) ligands. Simplified mechanistic views of the Cu(II)-assisted formation of the transformed ligands are proposed. Dc magnetic susceptibility studies in the 2-300 K range for the representative complexes 3-6 reveal the presence of very strong antiferromagnetic Cu(II)Cu(II) exchange interactions in the dinuclear complexes 3, 5, and 6 and within the dimeric {Cu2(OMe)(NO3){(py)(ph)CO}(LC)}(+) subunits of 4. The strong antiferromagnetic coupling is discussed in terms of the large Cu-O-Cu angles (101.0-102.9°) in the dinuclear, planar {Cu2O2} units/subunits of 3-6.

Crystal structure of (μ-4-hy-droxy-benzene-thiol-ato-κ(2) S:S)bis-(μ-phenyl-methane-thiol-ato-κ(2) S:S)bis-[(η(6)-1-isopropyl-4-methyl-benzene)-ruthenium(II)] tetra-fluorido-borate.

The crystal structure of the dinuclear arene ruthenium title complex, [Ru2(C6H5OS)(C7H7S)2(C10H14)2]BF4, shows the two Ru(II) atoms to be bridged by two benzyl-thio-pheno-late units and one 4-hy-droxy-thio-pheno-late unit, with the remaining three coordination sites of each Ru(II) atom being occupied by p-cymene ligands, completing the typical piano-stool coordination geometry. The BF4 (-) counter-anion is surrounded by four cationic dinuclear complexes, showing an O-H⋯F hydrogen bond and several weak C-H⋯F inter-actions. This is the first example of an X-ray analysis of a mixed dinuclear tri-thiol-ate arene ruthenium(II) complex.

Copper aromatic dicarboxylate complexes with a very long conformationally flexible dipyridyl ligand: Coordination polymers and a supramolecular nanotube

Hydrothermal reaction of copper nitrate and aromatic dicarboxylate precursors with the conformationally flexible and very long-spanning dipyridylamide ligand propane-1,3-diylbis(piperidine-4,1-diyl)bis(pyridin-4-ylmethanone) (4-ppbp) has generated three coordination polymers and a threaded-loop supramolecular complex. {[Cu(tere)(4-ppbp)(H2O)]·1.5H2O}n (1, tere=terephthalate) and {[Cu(iph)(4-ppbp)(H2O)]·2H2O}n (2, iph=isophthalate) both display slab motifs built from interdigitated (4,4) grid layers. {[Cu2(phda)(phdaH)2(4-ppbp)2]·6H2O}n (3, phda=1,4-phenylenediacetate) possesses a 4-connected 658 cds network with self-penetration of 8-membered circuits. {[Cu2(phtH)2(4-ppbp)2(H2O)4](NO3)2·H2O}n (4, pht=phthalate) manifests ring-like dinuclear coordination complex cations with anionic phtH ligands projecting into supramolecular tubes with an inner diameter of approximately 12Å. Dehydration and thermal degradation properties of these new materials are discussed. We also report the crystal structure of the recrystallized dipyridylamide, 4-ppbp·2H2O.