ZnCl2 Complexes Research Articles

Synthesis and spectral characterization of 1,3-bis-(1H-benzimidazol-2-yl)-2-oxapropane complexes with various Zn(II) salts

1,3-Bis(1H-benzimidazol-2-yl)-2-oxapropane (L) complexes with ZnX2 (X=Cl−, Br−, I−, CH3COO−, NO3−, ClO4−) (1–6) were synthesized and characterized by elemental analysis, molar conductivity, TGA, FT-IR, NMR, ESI-MS and fluorescence spectroscopy. In addition, the crystal structure of [1,3-bis(1H-benzimidazol-2-yl)-2-oxapropane-κ2N,N′]dibromozinc(II) {2, [Zn(L)Br2]}, is reported. The Zn(II) ion has a tetrahedral environment in the chelate complex. The ZnCl2 complex (1) is structurally different from the others: It shows a broad signal at 7.28ppm in the 1H NMR spectra assigned to two coordinated water molecules. The very low solubility of the acetate complex (4) leads us to suggest a polymeric structure with [Zn2(μ-OAc)4(L)2]n paddlewheel units. The ligand shows from two to four emission bands in polar solvents. Compared to the ligand, the complexes show weak fluorescence intensity in ethanol and exhibit red- or blue-shift.

Novel applications of functionalized 2,1,3-benzothiadiazoles for coordination chemistry and crystal engineering

Two novel applications of functionalized 2,1,3-benzothiadiazoles for metal coordination chemistry and crystal engineering of organic solids are presented. 4-Amino-2,1,3-benzothiadiazole (1) forms a 2 : 1 complex with ZnCl2 (complex 2) and a 1 : 1 complex with 4-nitro-2,1,3-benzothiadiazole (3) (complex 4). The structures of compounds 1–4 were confirmed by single-crystal X-ray diffraction and studied by UV-Vis and IR spectroscopy, and DFT and QTAIM calculations. Complex 2 is the first structurally defined Zn complex with 2,1,3-benzothiadiazole ligands. In this complex, both molecules 1 are coordinated to Zn only by amino groups, thus revealing a novel type of coordination of this ligand to the metal center. According to 1H NMR data, complex 2 dissociates in CHCl3, THF or DMSO solutions. There are only a few examples of similar complexes, which are also considered to dissociate in solutions. In crystalline complex 4, molecules 1 and 3 form infinite alternating π-stacks connected by lateral S⋯N interactions between the neighboring stacks. Intermolecular S⋯N interactions are also observed in the crystals of individual 1 and 3 but the packing motifs are different from those in 4. DFT calculations predict a small charge transfer (CT, ∼0.02e at B97-D3 level) from 1 to 3 upon the formation of 4, which therefore is an unprecedented CT complex where both donor and acceptor moieties are the derivatives of the 2,1,3-benzothiadiazole ring system. This finding creates some new prospects for the crystal engineering of organic solids. Crystalline complex 4 is characterized by an intense CT absorption band with a maximum at ∼550 nm. However, according to DFT and QTAIM calculations the complex is weakly bonded and its formation is not observed in CH2Cl2 solution with 1H NMR and UV-Vis techniques.

Tetrathiafulvalene-s-tetrazine: versatile platform for donor–acceptor systems and multifunctional ligands

The structurally characterized tetrathiafulvalene-1,2,4,5-tetrazine donor–acceptor system shows redox tuneable intramolecular charge transfer, solvatochromic and electrochromic behaviour. Attachment of a dipicolyl-amine chelating unit affords a multifunctional ligand, which allows the preparation of the ZnCl2 complex in which an anion-π interaction is seen.

Synthesis and Structural Diversity of ZnCl2 and Zn(C6F5)2 Complexes of a Phosphinimine Ligand

AbstractZinc complexes of the potentially bidentate neutral monophosphinimine ligand 4‐(ArN=PPh2)dibenzofuran were prepared. Two derivatives of this framework were studied, which differ in the steric demand of the N‐aryl group (Ar = Dipp, Mes). The ligand interacts with diethylzinc in solution but does not form a tightly bound complex, whereby the degree of association is found to be dependent on temperature. However, isolable complexes are formed upon reaction with the more Lewis acidic precursors ZnCl2 and Zn(C6F5)2. In this way, the ZnCl2 complexes 1 and 2 and Zn(C6F5)2 complexes 3 and 4 were prepared and structurally characterized. The nuclearity of 1 and 2 was shown to depend on the bulk of the ligand. Furthermore, the strength of the bonding interaction between the zinc atoms and the dibenzofuran oxygen atoms in 3 and 4 also depends on the choice of ancillary ligand. Attempts to further derivatize these complexes were unsuccessful, and thus, functionalization of the complex LZnEt(OTf) was undertaken instead, resulting in formation of the novel linear trinuclear complex 5.

An N-Heterocyclic Carbene−Disilyne Complex and Its Reactivity toward ZnCl2

The reaction of disilyne 1 with 1,3,4,5-tetramethylimidazol-2-ylidene (an N-heterocyclic carbene, NHC) produced the disilyne-NHC complex 2, RLSi═SiR: (R = Si(i)Pr[CH(SiMe(3))(2)](2), L = NHC), with a trans geometry of the Si═Si moiety and lone-pair electrons residing on one of the double-bonded Si atoms. Upon complexation of 2 with ZnCl(2), the disilyne-NHC-ZnCl(2) complex 3 was produced, in which the Si═Si bond adopted the cis geometry.

Synthesis and X-ray Crystal Structure of Dichloro[N-{6-methyl-2-pyridyl)methyl}-(S)-1-phenylethylamine]zinc(II) and Its Catalytic Application to rac-Lactide Polymerization

Poly(lactic acid) or polylactide (PLA) is a biodegradable synthetic polymer. A typical degradation time is months to years for L-PLA and weeks to months for rac-PLA. This time scale is several orders of magnitude shorter than that of petroleum-based polymers, which makes it possible to compost PLA waste just into soil amendments. In addition to this green benefit, PLA’s raw material is from annually renewable resources such as corn and sugar beats or even from the food wastes. Moreover, basic physical properties of PLA that include narrow MWD, low haze, high mechanical strength, high gas permeability and easy processibility are acceptable enough to utilize this material in many applications such as fiber, film, and blow molding. Due to these merits not to mention skyscraping natural oil price, PLA have emerged as an environmentally friendly plastic materials that can replace many petroleum-based ones. It has been known that the catalyst-initiated ring-opening polymerization reaction of purified lactide is advantageous over the condensation reaction of lactic acid in terms of a higher polymerization rate, a higher MW, and a better conversion. Among many different kinds of metal species for the polymerization catalysts, relatively non hazardous magnesium and zinc, or aluminum have attracted more attention than highly toxic tin, lead and bismuth, or lanthanides because the major application fields of PLA are biomedical and food packaging and even ppm level catalyst residues are potentially harmful for these application. Along this line, we attempted to prepare PLA with the newly synthesized zinc complex ligated by the chiral N-{6-methyl-2-pyridinyl)methyl}-(S)-1-phenylethylamine (MPMA) ligand. Instead of a direct complexation reaction between MPMA and dialkylzinc to prepare an active catalyst species as in our previous work, we first synthesized air and moisture stable (MPMA)ZnCl2 complex and generated the active catalyst species by treating it with benzylmagnesium chloride (BnMgCl) in situ. Herein, we report the synthesis of MPMA ligand as well as its ZnCl2 complex, the X-ray crystal structural characterization of the complex, and the polymerization results of rac-lactide with in situ generated (MPMA)ZnBn2.

Chelating Complexes of Diethylzinc and ZnCl2 with 2,2‐Bipyridine and 1,6,7,12,13,18‐Hexaazatrinaphthylene (HATN) as Ligands

AbstractThe 1,6,7,12,13,18‐hexaazatrinaphthylene (HATN) complex [(Et2Zn)3(μ3‐HATN)] was synthesized and characterized by IR spectroscopy, UV/Vis spectroscopy, elemental analysis and ESI‐MS spectrometry. Attempts to prepare ZnCl2 complexes of HATN leads only to the mononuclear [(Cl2Zn)(HATN)] derivative, characterized by X‐ray diffraction, IR‐ and UV/Vis‐spectroscopy as well as ESI‐MS spectrometry. The bright red 2,2′‐bipyridine (bipy) complex [(Et2Zn)(bipy)] (1) was synthesized and characterized by X‐ray diffraction and NMR spectroscopy. The UV/Vis‐spectra of the HATN‐complexes show absorptions in regions of far longer wavelengths than the corresponding 2,2′‐bipyridine or 1,10‐phenantroline complexes. Consequently the π*‐LUMO of HATN (5) is lower in energy than the π*‐LUMO of 2,2′‐bipyridine (2) or 1,10‐phenanthroline (phen).

Facile routes to Alkyl-BIAN ligands

The Alkyl-BIAN ligands tert-Butyl-BIAN and 1-Adamantyl-BIAN have been synthesized and their structures have been determined by single-crystal X-ray diffraction along with that of the ZnCl2 complex of tert-Butyl-BIAN.

Dichloro(di-2-pyridylamine)zinc(II): a redetermination at 110 K

The title compound, [ZnCl2(C10H9N3)], has been investigated at 110 K. In contrast with the previously published room-temperature structure [Ho et al. (1999). J. Chem. Soc. Dalton Trans. pp. 1581–1586], the amine N atom is found to have a symmetrical planar environment. The two independent Zn—Cl distances are significantly different, but the difference of 0.0414 (3) Å is within the range found in other tetra­hedral ZnCl2 complexes.

A Water‐Soluble Calix[4]arene‐Based Podand Incorporating 4,4′‐Dicarboxy‐2,2′‐bipyridine Chelating Units − Synthesis and Complexation Properties towards Copper Ions

AbstractA water‐soluble calix[4]arene‐based podand has been prepared by incorporation, at the lower rim, of two 4,4′‐dicarboxy‐2,2′‐bipyridine units in opposite positions. The association between its coordination and hydrophilic properties were beneficial to the complexation and solubilization of copper(I) in water, even in the presence of bovine serum albumin. The ligand and its corresponding CuI complex have been fully characterized, but attempts to crystallize them have been unsuccessful so far. For this reason, the dinuclear ZnCl2 complex of the organic solvent soluble tetraester intermediate has been crystallized, and subjected to X‐ray diffraction analysis, confirming the expected podand‐like structure of the ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Crystal Structures of 9,10-Bis[bis(2-pyridylmethy)aminomethyl]anthracene and Its ZnCl2 Complex. Intramolecular π–π Interaction between Anthracene and ZnCl2-complexed Pyridine

Abstract Anthracene derivatives having dipicolylaminomethyl group exhibited an emission-intensity enhancement in the presence of Zn2+. On the basis of an X-ray crystallographic analysis, the binding of Zn2+ to the dipicolylaminomethyl unit inhibits the photoinduced electron transfer process. Intramolecular π–π interactions between the anthracene and the ZnCl2-complexed pyridine were observed.

Synthesis and characterization of methyl methacrylate/styrene hyperbranched copolymers via living radical mechanism

Free-radical copolymerizations of N,N-diethylaminodithiocarbamoylmethylstyrene (inimer: DTCS) with a methyl methacrylate (MMA)/zinc chloride (ZnCl2) complex were carried out under UV light irradiation. DTCS monomers play an important role in this copolymerization system as an inimer that is capable of initiating living radical polymerization of the vinyl group. The reactivity ratios (r1 = 0.56 and r2 = 0.52: DTCS [M1]; MMA [M2]) obtained for this copolymerization system were different from a corresponding model system (alternating copolymer) of a styrene and MMA/ZnCl2 complex (r1 = 0.25 and r2 = 0.056). It was found that the hyperbranched copolymers produced exhibited a random branching structure. It was found that the Lewis acid ZnCl2 formed the complex not only with MMA but also with the carbamate group of inimer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2490–2495, 2003

Zinc Complexation in Hydrothermal Chloride Brines: Results from ab Initio Molecular Dynamics Calculations

We determined the coordination environment of Zn2+ in aqueous Cl- brines at 25 °C and 300 °C using ab initio molecular dynamics simulations. The ZnCl+ and ZnCl2 complexes exist as pseudo-octahedral ZnClm(H2O)6-m clusters at 25 °C but occur as pseudo-tetrahedral ZnClm(H2O)4-m clusters at 300 °C. The ZnCl3- complex occurs as the pseudo-tetrahedral ZnCl3(H2O)- cluster at 25 and 300 °C. The tetrahedral ZnCl42- complex, however, is the dominant Zn−Cl complex at 25 °C, at least in highly concentrated (7.4 m) Cl- brines. The change in hydration number with temperature for the ZnCl+ and ZnCl2 complexes will complicate extrapolations of solvation energies to hydrothermal conditions using a Born-model-based equation of state.

Structural and spectroscopic studies of the versatile coordination chemistry of the chiral ligand N,N-bis(1-propan-2-onyl oxime)-L-methionine N'-methylamide with Ni(II) and Zn(II).

The potentially pentadentate, chiral ligand N,N-bis(1-propan-2-onyl oxime)-L-methionine N'-methylamide (L-MABO) shows remarkable versatility in its coordination chemistry with Ni(II) and Zn(II). In the crystal structure of the ZnCl2 complex of L-MABO, the ligand coordinates to the metal only through its three nitrogen donor groups (one amine and two oximes), with two chloride anions completing the distorted trigonal bipyramidal coordination sphere. In the NiCl2 complex, the three nitrogen donors and the thioether sulfur coordinate, along with two chlorides. The crystal structure of the Ni(NO3)2 complex contains two independent molecules, one of which coordinates the three nitrogens, the thioether sulfur, and the amide oxygen of L-MABO in addition to one nitrate anion. The second molecule coordinates the three nitrogen donors, the amide oxygen, one nitrate anion, and a methanol molecule. Thus, in only three crystal structures, L-MABO demonstrates its ability to provide N3, N3S, N3O, and N3OS donor sets. The thioether-bound complexes are unusual in that they have a predominantly nitrogen environment with a nickel-thioether bond that is not constrained by surrounding donor groups in a macrocyclic or linear polydentate motif. Comparison of the thioether-coordinated and methanol-coordinated molecules in the Ni(NO3) salt of L-MABO demonstrate the effect of the thioether bond on the relative "hardness" of the nickel. The electronic absorption and circular dichroism spectra of the aqueous solutions of the nickel complexes are interpreted in terms of a "descent in symmetry" model based on successive C3v and Cs distortions from octahedral geometry. These ligand field spectra indicate that in aqueous solution all ligand groups except for the three nitrogens of L-MABO are displaced by water. In acetonitrile, the non-nitrogen donors in the nitrate salt may also be displaced, while the chlorides remain coordinated.

Physicochemical properties of complexes of zinc iodide with pyridine N-oxides

Polycrystalline 1 : 2 complexes of ZnI2 with N-oxides of pyridine, picoline, and 2,6-lutidine were studied by IR spectroscopy, dielectrometry, and conductometry. An equilibrium between three solid phases was observed. These phases are characterized by different enthalpies of formation of intermolecular bonds and different mechanism of electronic effect transmission via these bonds. Gas-like thermal molecular motion in one of the phases of the 2,6-lutidine N-oxide complex was observed. Reversible chemical reactions on the surface of the crystalline 3-picoline N-oxide complex are initiated on exposure to an alternating electric field. Two complexes, similarly to the ZnCl2 complexes, are ionized in the cumulative mode on fast heating from 18-19 to 26-45°C. Partial activation energies of electrical conductivity of different ions were determined for a number of complexes and inorganic salts.

Reactivity of copper(I) and (II) and zinc(II) complexes of bis-(t-butyl)thiosalen and the crystal structure of the stable Cu(I) complex

A study of the de-t-butylation properties of the N2S2 ligand N,N′-bis{[2-(1,1-dimethylethylthio)phenyl]methylene}-ethane-1,2-diamine (L1) has shown that in contrast to its behaviour with Ni(II) it will not undergo de-t-butylation, using the conventional conditions, with Cu(I) or Zn(II) and not cleanly with Cu(II). The air stable perchlorate salt of the Cu(I) complex of L1 has been isolated and its crystal structure determined. The complex has a distorted tetrahedral structure in which the ligand binds in such a way as to produce the diastereomeric form of the complex in which both t-butyl groups are directed away from the centre of the molecule and from each other. Cyclic voltammetry in nitromethane indicated that the Cu(II) complex of L1 is chemically unstable, which was verified during synthetic studies in which it was seen to be prone to both hydrolysis and partial de-t-butylation. Spectroscopic and conductometric evidence suggest that in the ZnCl2 complex of L1 coordination of chloride occurs to the exclusion of both thioether moieties.

Effect of ZnCl2 on the spontaneous copolymerization of methyl acrylate with substituted 1,3‐dienes

AbstractThe reactions of the mildly electron‐poor olefin methyl acrylate (MA) with three electron‐rich substituted hydrocarbon 1,3‐dienes, namely 2,3‐dimethyl‐1,3‐butadiene (DMB), 4‐methyl‐1,3‐pentadiene (MPD) and isoprene (IP) were investigated in 1,2‐dichloroethane in the presence of various amounts of zinc chloride at different temperatures. ZnCl2 complexes with the ester group of MA and increases the MA's electron‐poor character and therefore its tendency towards reactions with electron‐rich dienes. In the absence of ZnCl2, no reaction occurs between the investigated dienes and MA under the used reaction conditions. Both alternating copolymers and [4+2] cycloadducts formed spontaneously in the presence of ZnCl2 even at room temperature. The structure of the diene and its nucleophilicity control the product distribution. For the DMB and IP systems, raising the reaction temperature and increasing the ZnCl2 concentration enhance the overall reaction rate and in most cases also favor the cycloaddition over the copolymerization. IP is less reactive than DMB. With MPD only copolymer is formed because the two terminal methyl groups retard the concerted [4+2] cycloaddition. These results are in agreement with a postulated mechanism involving competition between the formation of a π‐allyl 2‐hexene‐1,6‐diradical, capable of initiating free radical copolymerization, and concerted [4+2] Diels‐Alder cycloaddition.

Zinkkomplexe von Aminosäuren und Peptiden, 2[1]. Koordination einfacher Histidin‐Derivate an Zink

Zinc Complexes of Amino Acids and Peptides, 2[1]. – Coordination of Simple Histidine Derivatives to ZincThe bis(L‐histidine)ZnCl2 complex 1 is likely to have tetrahedral ZnN2Cl2 coordination. For the compound (L‐histidine)‐ZnCl2 · HCl (2) a structure determination has revealed a tetrahedral ZnOCl3 coordination. Of the C‐protected histidine derivatives His‐OMe and His‐NH2 and zinc salts of non‐coordinating anions the complexes (His‐OMe)2ZnX2 (3) and (His‐NH2)2Zn(ClO4)2 (4) were obtained. A structure determination of (His‐OMe)2Zn(BPh4)2 · H2O has revealed a ZnN4 coordination with chelating histidine units. Of the N‐protected histidine derivative Nα‐acetylhistidine the complexes (Ac‐His)ZnX · H2O (5, X = ClO4, BF4) have been isolated which are coordination polymers in the solid state. From pH‐dependent 13C‐NMR studies it is concluced that in solution the imidazole N and carboxyl O are coordinated to zinc in (Ac‐His)Zn and (Ac‐His)2Zn units. The doubly protected histidine derivative Bz‐His‐OMe acts as a monodentate ligand forming the tetrahedral complexes (Bz‐His‐OMe)4Zn(ClO4)2 (6) and [(Bz‐His‐OMe)2Zn(2,9‐dimethyl‐o‐phenanthroline)](ClO4)2 (7).

置換ビグアニドの合成法

It was found that amines added to the N-cyano group on cyanoguanidines in the presence of FeCl3 or ZnCl2 under mild conditions. For example, the reaction of cyanoguanidine [2a] with butylamine, proceeded at room temperature in the presence of FeCl3 to give butylbiguanide [1a] in 99% yield. Similarly, [2a] or N-cyano-N'-phenylguanidine [2b] reacted with diethylamine, benzylamine, hexadecylamine, octadecylamine and aniline at room temperature or under reflux in dioxane or tetrahydrofuran to give the corresponding biguanides [1].In the presence of ZnCl2, [2] and two equivalents of amines were heated in refluxing dioxane. The initial products, biguanides [1]-ZnCl2 complexes, were readily hydrolyzed by aqueous ammonia or amines to give hydropchlorides of [1].When N-substituted-N'-cyano-S-methylisothioureas [3] reacted with primary amines in the presence of FeCl3 or ZnCl2 the addition to the cyano group and the substitution of the methylthio group with amines occurred at the same time to yield the corresponding [1].

ChemInform Abstract: Regioselective 1,4‐Addition to α,β‐Unsaturated Ketones with Grignard Reagents Mediated by (N,N,N′,N′‐Tetramethylethylenediamine)zinc(II) Chloride.

AbstractIn the presence of the ZnCl2 complex (III), the Grignard reagents (II) react with α,β‐unsaturated ketones (I), giving predominantly the 1,4‐addition products (IV), together with small amounts of the 1,2‐addition products (V).