Structures Of Complexes 4a Research Articles

Preparation of trinuclear ruthenium clusters based on piconol ligands and their application in Oppenauer‐type oxidation of secondary alcohols

AbstractTreatment of Ru3(CO)12 with one equivalent of 2‐indolyl‐6‐pyridinyl‐alcohol ligands 2‐(C8H6N)‐6‐(CR1R2OH)C5H3N (R1 = R2 = Me (L1H); R1 = R2 = C2H5 (L2H); R1, R2 = −(CH2)4‐ (L3H);& R1, R2 = −(CH2)5‐ (L4H)) in refluxing THF afforded the corresponding trinuclear ruthenium clusters L(μ2‐H)Ru3(CO)9 (1a–1d), respectively. All the novel Ru complexes were well characterized by NMR, elemental analyses and IR spectra. Structures of complexes 1a, 1c, and 1d were further determined by X‐ray crystallographic studies. Complexes 1a–1d were applied to catalytic Oppenauer‐type oxidation of secondary alcohols with acetone as oxidant, and complex 1a was found to be the most efficient catalyst.

Influences of Fluorine Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization.

A series of iminopyridine complexes of Fe(II) and Co(II) complexes bearing fluorinated aryl substituents were synthesized for the polymerization of isoprene. The structures of complexes 3a, 2b and 3b were determined by X-ray diffraction analysis. Complex 3a contained two iminopyridine ligands coordinated to the iron metal center forming an octahedral geometry, whereas 2b adopted a chloro-bridged dimer, and 3b featured with two patterns of cobalt centers bridged via chlorine atoms. Complexes 2b and 3b represented rare examples of chlorine bridged bimetallic Co(II) complexes. The fluorine substituents effects, particularly on catalytic activity and polymer properties such as molecular weight and regio-/stereo-selectivity were investigated when these complexes were employed for isoprene polymerization. Among the Fe(II)/methylaluminoxane (MAO) systems, the 4-CF3 substituted iminopyridine Fe(II) complex 1a was found as a highly active isoprene polymerization catalyst exhibiting the highest activity of 106 g·(mol of Fe)−1·h−1. The resultant polymer displayed lower molecular weight (Mn = 3.5 × 104 g/mol) and moderate polydispersity index (PDI = 2.1). Furthermore, the ratio of cis-1,4-/3,4 was not affected by the F substituents. In the series of Co(II)/AlEt2Cl binary systems, complexes containing electron-withdrawing N-aryl substituents (R = 4-CF3, 2,6-2F) afforded higher molecular weights polyisoprene than that was obtained by the complex containing electron-donating N-alkyl substituents (R = octyl). However, ternary components system, complex/MAO/[Ph3C][B(C6F5)4] resulted in low molecular weight polyisoprene (Mn < 2000) with high trans-1,4-unit (>95%).

Synthesis of di- and trinuclear zinc complexes bearing pyrrole-based ligands and their catalysis toward the ROP of rac-lactides

Di(aminomethylpyrrolyl)methane derivatives [2-{5-R′2NCH2(C4H2NH)}]2CR2 (2a R = Et, R′ = Me; 2b R = Ph, R′ = Me; 2c R = Ph, R′ = Et; 2d R2 = 1,1′-biphenyl-2,2′-diyl, R′ = Me; 2e R2 = 1,1′-biphenyl-2,2′-diyl, R′2 = (CH2)4) were prepared through reaction of di(1H-pyrrol-2-yl)methane derivatives (2-C4H3NH)2CR2 (1a R = Et; 1b R = Ph;1c R2 = 1,1′-biphenyl-2,2′-diyl) with formaldehyde and amines. Treatment of 2a with 3 equiv. of ZnEt2 in toluene afforded trinuclear zinc conplex 3a, while respective reaction of 2b-2e with 3 equiv. of ZnEt2 in toluene or THF produced dinuclear zinc complexes 3b-3e. Each of the complexes was characterized by 1H and 13C NMR spectroscopy and elemental analysis. Structures of complexes 3a and 3b were additionally characterized by single crystal X-ray diffraction. Catalysis of complexes 3a-3e toward the ROP of rac-lactides was evaluated in both toluene and THF. Each complex was active in the catalysis in the presence of benzyl alcohol (BnOH). 3a showed the highest activity in toluene and 3c was the most active in THF. Kinetic study of complexes 3a and 3e was carried out and the results showed that the polymerization catalyzed by 3e/BnOH follows a first-order kinetics, while 3a/BnOH-catalyzed polymerization followed neither first-order nor second-order kinetics.

Mixed-ligand Zn(II) complexes of 1-phenyl-3-methyl-4-formylpyrazole-5-one and various aminoheterocycles: Synthesis, structure and photoluminescence properties

A series of eight adducts of aminoazoles and aminoazines of a bis-chelate Zn(II) on the basis of 1-phenyl-3-methyl-4-formylpyrazole-5-one (HL) of common formula [ZnL2(NH2Het)n] (n=1, 2) (3a–h), where NH2Het=1-aminoisoquinoline (3a), 6-aminoquinoline (3b), 3-aminoquinoline (3c), 5-amino-4,6-dimethylquinoline (3d), 2-aminopyridine (3e), 2-amino-5-bromopryridine (3f), 3-amino-5-methylisoxazole (3g), and 2-amino-1-ethylbenzimidazole (3h), were synthesized. Formulation of all compounds is based upon satisfactory C, H, N, Zn elemental analyses, IR, and 1H NMR spectrоscopies. The structure of complex 3a has been determined by X-ray single-crystal diffraction. Optical properties of zinc complexes were investigated by UV–vis and photoluminescence spectroscopy.

Half-metallocene complexes of yttrium with amidinate ligands: Monoalkyl yttrium formation and C–H bond activation

The treatment of half-metallocene dialkyl yttrium complexes (C5Me4SiMe3)Y(CH2SiMe3)2(THF) (1a) and (C5Me4SiMe2Ph)Y(CH2SiMe3)(THF) (1b) with carbodiimide (RNCNR, R=tBu, Cy, iPr) resulted in two different kind of yttrium complexes bearing bis(amidinate) ligands. The reaction of complex 1a gave THF-free monoalkyl complexes (C5Me4Me3Si)Y(CH2SiMe3)[(RN)2C(CH2SiMe3)] (2a–c) as thermally robust crystals, while the reaction of complex 1b resulted in an ortho-metalated product 3, which contains a strained five-membered chelate ring formed by the C–H bond activation of the phenyl group. All resulted complexes were fully characterized by NMR spectroscopy and the structures of complexes 2a and 3 were confirmed by X-ray diffraction. Complexes 2a–2c show low to high activities for n-butyl acrylate polymerization to produce high molecular weight polymers.

Iminopyridine-Based Cobalt(II) and Nickel(II) Complexes: Synthesis, Characterization, and Their Catalytic Behaviors for 1,3-Butadiene Polymerization.

A series of iminopyridine ligated Co(II) (1a–7a) and Ni(II) (1b–7b) complexes were synthesized. The structures of complexes 3a, 4a, 5a, 7a, 5b, and 6b were determined by X-ray crystallographic analyses. Complex 3a formed a chloro-bridged dimer, whereas 4a, 5a, and 7a, having a substituent (4a, 5a: CH3; 7a: Br) at the 6-position of pyridine, producing the solid structures with a single ligand coordinated to the central metal. The nickel atom in complex 5b features distorted trigonal-bipyramidal geometry with one THF molecule ligating to the metal center. All the complexes activated by ethylaluminum sesquichloride (EASC) were evaluated in 1,3-butadiene polymerization. The catalytic activity and selectivity were significantly influenced by the ligand structure and central metal. Comparing with the nickel complexes, the cobalt complexes exhibited higher catalytic activity and cis-1,4-selectivity. For both the cobalt and nickel complexes, the aldimine-based complexes showed higher catalyst activity than their ketimine counterparts.

Structural Influencing Factors on ZnII/CdII Coordination Polymers Based on Tri‐pyridyl‐bis‐amide: Assembly, Structures, Fluorescent Sensing and Selective Photocatalysis

AbstractFourteen new ZnII/CdII coordination polymers tuned by semi‐rigid “V”‐like tri‐pyridyl‐bis‐amide ligands with different spacers and different dicarboxylates co‐ligands, namely, {[Zn(L1)(mip)]·H2O}n (1), {[Zn2(L1)2(hip)2]·H2O}n (2), {[Zn(L1)(oba)]·H2O}n (3), {[Zn(L1)(chda)]·H2O}n (4), {[Cd2(L1)(mip)2(H2O)]·2H2O}n (5), {[Cd(L1)(hip)]·4H2O}n (6), {[Cd(L1)(oba)]·H2O}n (7), {[Cd3(L1)(chda)3]·4H2O}n (8), [Zn(L2)(mip)]n (1a), {[Zn(L2)(hip)(H2O)]·3H2O}n (2a), [Zn(L2)(oba)]n (3a), {[Cd(L2)(hip)]·3H2O}n (6a), {[Cd(L2)(oba)]·H2O}n (7a), [Cd(L2)(chda)]n (8a), [L1 = N,N′‐di(pyridin‐3‐yl)pyridine‐2,6‐dicarboxamide, L2 = N,N′‐di(pyridin‐3‐yl)pyridine‐3,5‐dicarboxamide, H2mip = 5‐methylisophthalic acid, H2hip = 5‐hydroxyisophthalic acid, H2oba = 4,4′‐oxybis(benzoic acid), H2chda = trans‐1,4‐cyclohexanedicarboxylic acid] have been hydrothermally synthesized and structurally characterized. Complexes 1–4 based on the same L1 ligand and ZnII ion show various structures. Complex 1 features a two‐dimensional (2D) network, which consists of a linear [Zn‐mip]n chain and [Zn‐L1]n left‐, right‐handed helixes. Complex 2 is a twofold interpenetrating 2D→2D network. In complex 3, Zn2(L1)2 loops were connected by oba anions creating a 1D channel‐like structure. Complex 4 is a 2D layer containing [Zn‐chda]n right‐handed helixs and Zn2(L1)2 loops. Complexes 5–8 with CdII ion exhibit different structures. Complex 5 features a 1D belt structure based on Cd4(COO)4 subunits. However, complex 6 exhibits a 2D network constructed from [Cd‐hip]n ladder‐like chains and Cd2(L1)2 loops. Complex 7 shows a 1D double chain structure containing [Cd‐oba]n zigzag chain and [Cd‐L1]n meso‐right‐handed helix. Complex 8 exhibits a 2D network based on 2D [Cd‐chda] layer and 1D [Cd‐L1]n meso‐helical chain. For complexes 1a–8a based on L2 ligand, complex 1a is a 2D layer containing [Zn‐mip]n linear chain and [Zn‐L2]n meso‐helical chain. The structure of complex 2a is very similar to that of 3. Complex 3a exhibits a 2D grid network containing 1D [Zn‐oba]n and [Zn‐L2]n chains. Complex 6a shows a 2D layer based on [Cd2(hip)2]n double chain and [Cd‐L2]n chain. The structure of complex 7a is very similar to that of 7. Complex 8a is a 3,5‐connected 3D framework with the Schläfli symbol of (42.65.83)(42.6), which is constructed from [Cd‐L2]n channel‐like chains and chda linkers. The structural diversity of the title complexes indicates that the tri‐pyridyl‐bis‐amide ligands with different spacers, the dicarboxylates and central metals play important roles in tuning the dimensionalities and structures of the target complexes. The title complexes exhibit excellent photocatalytic activity and selectivity for organic dyes degradation under UV light. In addition, fluorescent sensing behaviors of 3, 6, 7 and 7a toward different organic solvents have been investigated in detail.

Synthesis and characterization of zinc complexes supported by NHC-based CNN- and CNP-tridentate ligands and their catalysis in the ring-opening polymerization of rac-lactide and ε-caprolactone

A series of zinc complexes bearing NHC-based C,N,N- or C,N,P-tridentate ligands were synthesized and characterized and the catalysis of the complexes toward the ring-opening polymerization of rac-lactide was evaluated. The ligand precursors ▪ (2a, R = Me; 2b, R = iPr) prepared from ▪ (R = Me or iPr) and Ph2PCH2Py were successively treated with nBuLi and ZnEt2 to afford corresponding zinc complexes ▪ (3a, R = Me; 3b, R = iPr). Similar treatment of ▪ (4a) (prepared from ▪ and Ph2PCH2PPh2) with nBuLi and then ZnEt2 gave ▪ (5). Treatment of ▪ (4a, R = Me, X = I; 4b, R = Bn, X = Br; 4c, R = iPr, X = I) with p-MeC6H4N3 resulted in ▪ (6a, R = Me, X = I; 6b, R = Bn, X = Br; 6c, R = iPr, X = I). The reaction of 6a with nBuLi and ZnEt2 in sequence produced ▪ (7). Whereas the reaction of 6a–c with an equimolar amount of ZnEt2 gave ▪ (8a, R = Me, X = I; 8b, R = Bn, X = Br; 8c, R = iPr, X = I). All new compounds were characterized by 1H, 13C and 31P NMR spectroscopy and elemental analyses. The structures of complexes 3a, 5 and 8b were additionally characterized by single crystal X-ray diffraction. In the presence of BnOH complexes 3a, 3b, 5 and 7 catalyze the ring-opening polymerization of rac-lactide at room temperature and 3a, 3b, and 5 exhibited high activity. Complexes 8a–c are inactive under the same conditions. Complexes 3a and 5 were also tested for the catalysis in the ROP of ε-caprolactone and both showed good catalytic activity.

Non-symmetrically substituted ruthenocenes: synthesis, structures, and bond nature. Electronic effects of substituents in ruthenocene

Non-symmetrically substituted ruthenocenes CpRuCp´ (Cp´ = C5H4CHO (1a), C5H4COMe (1b), C5H4SiMe3 (1c), 1,3-C5H3(SiMe3)2 (1d), and Cp* (1e)) were synthesized in high yields by the reaction of [CpRu(MeCN)3]+ with cyclopentadienide anions. The structures of complexes 1a,b,d were determined by X-ray diffraction analysis. According to the energy partition analysis data, donor substituents strengthen the interaction between the [RuCp]+ and Cp´– fragments, whereas acceptor substituents weaken the interaction. This bond is predominantly electrostatic (56—59%). Based on the calculated electrostatic potentials at the ruthe-nium nucleus, it is shown that the donor ability of the substituents decreases in the following order: NMe2 > NH2 > OMe > Me ≈ OH > Rc > Fc ≈ Allyl ≈ H > SiMe3 > CH=CH2 ≈ Ph > PH2 > > SH ≈ F > SiH3 ≈ C≡CH > Cl > Br ≈ I ≈ COOMe > COOH > COMe > CF3 > CHO > CN > NO2.

Chiral nickel(II) and palladium(II) catalysts bearing strong electron‐withdrawing fluorine groups: synthesis, characterization and their application in catalytic polymerization for ethylene and styrene

A series of new chiral and achiral nickel(II) and palladium(II) complexes, {bis[N,N′‐(2,6‐diethyl‐4‐naphthylphenyl)imino]‐1,2‐dimethylethane}dibromonickel 3a, {bis[N,N′‐(4‐fluoro‐2‐methyl‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel rac‐(RS)‐3b, {bis[N,N′‐(4‐fluoro‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel rac‐(RR/SS)‐3c and {bis[N,N′‐(4‐fluoro‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dichloropalladium rac‐(RR/SS)‐3d were successfully synthesized and characterized. The molecular structures of representative ligand rac‐(RS)‐2b, nickel complex 3a, rac‐(RR/SS)‐3c and palladium complex rac‐(RR/SS)‐3d were determined by X‐ray crystallography. The structures of complexes 3a and rac‐(RR/SS)‐3c have pseudo‐tetrahedral geometry about the nickel center, showing C2 molecular symmetry. However, the structure of palladium complex rac‐(RR/SS)‐3d has pseudo‐square planar geometry about the palladium center, showing C2 molecular symmetry. Complex 3e {bis[N,N′‐(2,6‐dimethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel was also synthesized for comparison. Nickel complex rac‐(RS)‐3b bearing strong electron‐withdrawing fluorine group in the para‐aryl position and a chiral sec‐phenethyl group in the ortho‐aryl position of the ligand (one methyl group in the ortho‐aryl position) displays the highest catalytic activity for ethylene and styrene polymerization, and produced highly branched polyethylene and syndiotactic‐rich polystyrene. However, palladium complex rac‐(RR/SS)‐3d shows low catalytic activity for ethylene and styrene polymerization due to the poor leaving group, Cl, attached to palladium and the unfavorable molecular structure. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Bismuth(III) halides as halide source for preparation of dihaloplatinum(IV) complexes

The complexes [PtMe2(tBu2bpy)], 1a, tBu2bpy=4,4′-di-tert butyl-2,2′-bipyridine, and [PtMe(ppy)PPh3], 1b, ppy=deprotonated 2-phenylpyridine, react very easily with BiX3 (X=Cl, Br, or I) to give [PtMe2(X)2(tBu2bpy)] (2a, X=Cl; 3a, X=Br; 4a, X=I) and [PtMe(X)2(ppy)PPh3] (2b, X=Cl; 3b, X=Br; 4b, X=I), respectively. In these oxidative addition reactions, BiX3 reagent can be used as halide source instead of hazardous reagents X2. The dihaloplatinum(IV) complexes are characterized using NMR spectroscopy and the structures of complexes 4a and 3b are further identified by X-ray crystallography. Structures of Pt(IV) complexes are investigated using DFT calculations at B3LYP level of theory.

Mono- and dinuclear Hg(II) complexes of bis-(N-heterocyclic carbene) bridged with calixarene fragments: Synthesis, structure and sensing behavior

Mono- and dinuclear Hg(II) complexes of bis-(N-heterocyclic carbene) bridged with calixarene fragments, [HgL](PF6)2 (4a, 4b) and [Hg2L2](PF6)4 (5a, 5b), (L = bis{3-(N-1-naphthylmethyl-imidazol-2-ylidene)methyl-5-R-2-methoxyphenyl}methane, a: R = Me, b: R = t-Bu) were both obtained by treatment of corresponding bis-imidazolium salts with mercuric acetate. The structures of complexes 4a and 5a were established by X-ray diffraction. Mononuclear complex 4a displays a small rigid cavity consisting of a mercury cation and a bis-NHC ligand. Dinuclear complex 5a shows a 28-memebered metallamacrocycle formed by two mercury cations and two bis-NHC ligands. Short mercury–oxygen contacts are found between mercury cations and methoxy groups of ligands in 4a and 5a. Cation–π–arene interactions are present between mercury cations and naphthalene rings of ligands. Additionally, the fluorescent chemosensing behaviors of complex 5a with large cavity to diphenylacetylene, (E)-azobenzene and (E)-4,4′-azobispyridine were investigated.

Dinuclear Macrocyclic Quinoline Bridged Mercury and Silver Bis(N‐heterocyclic Carbene) Complexes: Synthesis, Structure, and Spectroscopic Studies

AbstractQuinoline bridged imidazolium precursors 5,8‐bis(N‐R‐imidazolylidenylmethylene)quinoline PF6– salts [H2L](PF6)2 [R = Me (1a), R = naphthylmethyl (1b)] were prepared by quaternization of N‐methylimidazole and N‐naphthylmethylimidazole with 5,8‐bis(bromomethyl)quinoline, respectively. Reaction of the imidazolium ligands 1a and 1b with Hg(OAc)2 and Ag2O in acetonitrile gave the macrocyclic transition metal carbene complexes [Hg2L2](PF6)4 (2a and 2b) and [Ag2L2](PF6)2 (3a and 3b), respectively. All the N‐heterocyclic carbene complexes were characterized in detail by NMR, ESI‐MS, and elemental analysis. Structures of complexes 2a and 3a were determined by X‐ray diffraction studies. Structural studies revealed that the coordination arrangement of the central mercury atom in complex 2a displays a tricoordinate mode and the molecular conformation results in a“closed” form with the bridging quinoline functionality in the macrocycle, whereas the silver complex 3a does not show an coordiantion between the bridging quinoline and the AgI ion, which results in an “open” conformation of the macrocycle. The HgII and AgI NHC complexes showed similar UV absorption and luminescence in acetonitrile solutions.

Synthesis, Characterization, and Crystal Structures of Heteroannular Cyclopalladated Ferrocenylimine-Pyridine Complexes

Two new heteroannular cyclopalladated ferrocenylimine-pyridine derivatives, 2a and 2b, were easily prepared by the reaction of chlorine-bridged binuclear palladium complexes, 1a and 1b, with pyridine in high yields. They were characterized by ESI-MS, H-NMR, and IR spectra. The detailed structures of complexes 2a and 2b were determined by single-crystal X-ray analysis. According to the crystal structure, the palladium atom is bound to the unsubstituted Cp ring, forming a new heteroannular pyridine-cyclopalladated large-membered metallocycle. Complex 2a exists as a dimer in the crystal due to intermolecular CH(CH˭N)···Cl hydrogen bonds, while 2b has a two-dimensional network structure formed by the intermolecular hydrogen bonds between the Cl atom with the adjacent C-H groups of Cp and pyridine.

Diorganotin (IV) Heptacoordinated Complexes Containing Pentadentate [N3O2] Ligands Derived From 5-Substituted-Salicylaldehydes and Diethylenetriamine: Synthesis, Characterization, and Molecular Structure

A series of heptacoordinated tin(IV) mononuclear complexes [(R′)2Sn(5-X-saldien)] (X = H, OCH3, NO2) were synthesized by reaction of dimethyl-, di-n-butyl-, di-n-octyl-, and diphenyltin (IV) oxides with the pentadentate Schiff base ligands saldienH2, 5-MeO-saldienH2, and 5-NO2-saldienH2. All of the complexes were characterized by IR, mass spectrometry, and 1H, 13C, and 119Sn NMR spectroscopies, and the spectra display chemical shifts corresponding to a seven-coordinated tin environment. The crystal structures of complexes 2a, 2d, and 4b were determined by X-ray diffraction. The complexes are isostructural and the tin atoms exhibit pentagonal-bipyramidal geometries with the methyl, n-butyl, and phenyl groups occupying the axial positions and the donor atoms from the ligand occupying the equatorial positions. A fluxional behavior was also observed that involves a dissociation-association mechanism of the N-Sn bonds.

SET Oxidation of Li/X Phosphinidenoid Complexes by TEMPO

Oxidation of in situ generated Li/X phosphinidenoid complexes [(OC)5W{(Me3Si)2CHP(X)Li/12-crown-4}] (X = F (2), Cl (6)) with TEMPO at −78 °C led to the lithium halogenophosphinite complexes [(OC)5W{(Me3Si)2CHP(X)OLi/12-crown-4}] (4) via an unknown pathway possibly involving transient P-nitroxyl complex derivatives (3). Whereas 4a (X = F) could be isolated directly, 4b (X = Cl) underwent facile hydrolysis to give the lithium phosphonite complex [(OC)5W{(Me3Si)2CHP(OH)OLi/12-crown-4}] (7) as the final product; the structures of complexes 4a and 7 were firmly established by single-crystal X-ray analysis. DFT calculations on the assumed intermediate P-nitroxyl complexes 3a,b reveal a preference for homolytic N–O over P–O bond cleavage, as underlined by the small bond dissociation energies (in kcal/mol: 3a, P–O 53.2 and N–O 26.0; 3b, P–O 35.4 and N–O 20.8).

Demethylation of the SMe2 substituent in metallacarboranes. Synthesis and structures of the complexes Cp*M(η-9-SMe-7,8-C2B9H10) (M = Rh, Ir)

The demethylation of the cations [Cp*M(η-9-SMe2-7,8-C2B9H10)]+ (1a,b) with PhCH2SNa affords neutral metallacarboranes Cp*M(η-9-SMe-7,8-C2B9H10) (2a: M = Rh; 2b: M = Ir). The reverse reaction can be performed by the treatment of complexes 2a,b with MeI in the presence of TlPF6. The structures of complexes 2a,b were determined by X-ray diffraction.

Palladium(II) complexes of dithiocarbamic acids: synthesis, characterization, crystal structure and DNA binding study

A series of distorted square planar palladium(II) complexes with dithiocarbamic acids of general formula [Pd(L)2], where L = 4-methylpiperazine-l-carbodithioic acid anion, morpholine-4-carbodithioic acid anion or 4-benzylpiperidine-l-carbodithioic acid anion for complexes 1a, 1b and 1c, respectively, have been synthesized. The complexes were characterized by physicochemical and spectroscopic methods; in addition, the structure of complex 1a was characterized by single crystal X-ray crystallography. The interaction of these palladium complexes with CT-DNA was investigated with the help of absorption and emission spectroscopy. The association constant Kb was deduced from the absorption spectra, while the number of binding sites and the binding constant were calculated from the fluorescence quenching data. The results suggest an intercalative interaction of the complexes with CT-DNA.

Synthesis, characterization, and butadiene polymerization of iron(III), iron(II) and cobalt(II) chlorides bearing 2,6-bis(2-benzimidazolyl)pyridyl or 2,6-bis(pyrazol)pyridine ligand

Iron(III), iron(II) and cobalt(II) complexes bearing neutral N,N,N-tridentate ligand (Fe(III)L1, 1a; Fe(III)L2, 1b; Fe(III)L3, 1c; Fe(III)L4, 2a; Fe(III)L5, 2b; Fe(III)L6, 2c; Fe(II)L1, 3a; Fe(II)L2, 3b; Fe(II)L3, 3c; Fe(II)L4, 4a; Fe(II)L5, 4b; Fe(II)L6, 4c; CoL1, 5a; CoL2, 5b; CoL3, 5c; CoL5, 6b and CoL6, 6c) have been synthesized from the metal chlorides (FeCl3, FeCl2·4H2O or CoCl2) by treating the corresponding ligands (2,6-bis(benzimidazol-2-yl)pyridine, L1; 2,6-bis(1′-ethylbenzimidazol-2′-yl)pyridine, L2; 2,6-bis(1′-benzylbenzimidazol-2′-yl)pyridine, L3; 2,6-bis(pyrazol)pyridine L4; 2,6-bis(3-methylpyrazol)pyridine, L5 or 2,6-bis(3,5-dimethylpyrazol)pyridine, L6. The complexes are characterized by FTIR and elemental analyses. The structures of complexes 1a, 1b, 3a, 3b, 3c, 4a, 5a, 5b, 5c and 6c are further confirmed by X-ray crystallographic analyses. Six coordination iron(III) (1a, 1b and 1c) and iron(II) (3c*DMF) complexes adopt a distorted octahedral configuration with the equatorial plane formed by the three nitrogen atoms and one chlorine atom, while the iron(II) (3a, 3b and 4a) and cobalt complexes (5a, 5b, 5c and 6c) adopt a trigonal bipyramidal configuration with the equatorial plane formed by the pyridyl nitrogen atoms and the two chlorine atoms. All complexes are evaluated as precursors for 1,3-butadiene polymerization in the presence of cocatalyst in toluene at room temperature. Iron(III) and iron(II) bearing the same ligand show comparable catalytic performance. The catalytic activity and selectivity are significantly influenced by the ligand structure, with the latter being tunable within a wide range from cis-1,4 to trans-1,4. Cobalt complexes, in combination with either MAO or aluminum chlorides shown high activity, and high cis-1,4-selectivity irrespective of the structure of ligand backbone.

Synthesis and Characterization of Platinum(II) Complexes with a Diazenecarboxamide‐Appended Picolyl‐Triazole Ligand

AbstractThe coordination of the diazenecarboxamides, which were functionalized with the 1‐(2‐picolyl)‐1H‐1,2,3‐triazole moiety 1, to platinum(II) were studied, where K2[PtCl4] and cis‐[PtCl2(DMSO)2] were used as the platinum sources. The picolyl‐triazole (pictri) binding unit enabled chelation to the metal centre through the 1,2,3‐triazole N2 and the pyridyl nitrogen atoms under mild reaction conditions. When cis‐[PtCl2(DMSO)2] was used, with CH2Cl2 or CH3CN as the reaction solvents, the pure, stable diamminedichloridoplatinum(II) complexes 2 were isolated by filtration in 39 to 83 % yield. The products were structurally characterized in solution by 1H, 13C and 195Pt NMR spectroscopy. The 195Pt NMR chemical shifts for 2 appear in the region of –2203 to –2207 ppm. The structure of complex 2a was confirmed by single‐crystal X‐ray crystallography. The formation of the platinum complexes 2 was monitored using NMR spectroscopy. The complexation with cis‐[PtCl2(DMSO)2] in [D7]dmf proceeded through several intermediates, as indicated by the 195Pt NMR spectra with resonances in the range of –3055 to –2907 ppm. Similarly, the reaction of cis‐[PtCl2(DMSO)2] with diazenecarboxamide, which was functionalized with the nonchelating 1‐(2‐aminoethyl)‐1,2,3‐triazole derivative, was examined by NMR spectroscopy.