Cationic η-allyl sulfide complexes of nickel(II) for the polymerization of butadiene in aqueous emulsion

Reaction of the dimeric allyl-nickel(II) chloro complex [Ni(η³-C₃H₅)(μ-Cl)]₂ (5) with sulfur donor ligands (L = L₁₀-L₁₃) in the presence of ( = 3,5-(CF₃)₂C₆H₃) gives the corresponding cationic mononuclear complexes of the type [Ni(η³-C₃H₅)(L)₂]⁺ (1-4) [L = L₁₀ = diphenyl sulfide (1); L = L₁₁ = 4,4′-thiodiphenol (2); L = L₁₂ = 4,4′-thio-bis(6-tert-butyl-o-cresol) (3); L = L₁₃ = 4,4′-thio-bis (6-tert-butyl-m-cresol) (4)]. All of these complexes were characterized by elemental analysis and NMR spectroscopy, as well as the representative complex 3 additionally by single-crystal X-ray analysis. In comparison to the known complex [Ni(η³-C₃H₅)(η⁶-BHT)][B] (BHT = 3,5-di-tert-butyl-4-hydroxytoluene), the herein described cationic complexes show an increased stability towards water. The activity of the complexes for butadiene polymerization in aqueous emulsions was studied.     

Synthesis, characterization, and norbornene polymerization of η-benzylnickel(II) complexes of N-heterocyclic carbenes

Neutral η¹-benzylnickel carbene complexes, [Ni(η¹-CH₂C₆H₅)(IiPr)(PMe₃)(Cl)] (3) (IiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(η¹-CH₂C₆H₅)(SIiPr)(PMe₃)(Cl)] (4) (SIiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(η³-CH₂C₆H₅)(PMe₃)(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of η³-benzylnickel carbene complexes, [Ni(η³-CH₂C₆H₅)(IiPr)(Cl)] (5) and [Ni(η³-CH₂C₆H₅)(SIiPr)(Cl)] (6) were carried out by the abstraction of PMe₃ from 3 and 4 by the treatment of B(C₆F₅)₃. The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(η³-CH₂C₆H₅)(NHC)(X)] (7, NHC = IiPr, X = O₂CCF₃; 8, NHC = IiPr, X = O₃SCF₃; 9, NHC = SIiPr, X = O₂CCF₃; 10, NHC = SIiPr, X = O₃SCF₃). The solid state structures of 3 and 10 were determined by X-ray crystallography. The η³-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 °C.     

Synthesis and magnetic properties of trinuclear nickel(II) complexes bridged by α-benzyldioximato groups

Four new NiII–NiII–NiII homotrinuclear complexes namely [Ni(-BD)2{NiL2}](ClO4)2 [L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (5-NO2-phen), 2,2-bipyridyl (bpy) or 4,4-dimethyl-2,2bipyridyl (Me2bpy) and (-BD)– = -benzyldioximato ion] have been prepared and characterized. Based on elemental analyses, i.r. spectra, conductivity measurements, extended -benzyldioximato-bridged systems consisting of three nickel(II) ions in which the central nickel(II) ion has a square-planar environment and the end capped two nickel(II) ions have a distorted octahedral environment are proposed for these structures. The temperature dependence of the magnetic susceptibility for complexes (1) (phen), (2) (5-NO2-phen), (3) (bpy) and (4) (Me2bpy) were measured over the 77–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator (H^ = –2JS^1S^2), giving the exchange integral J = –13.31 cm–1 for (1), J = –7.37 cm–1 for (2), J = –8.96 cm–1 for (3) and J = –7.33 cm–1 for (4) These results indicate a weak antiferromagnetic spin exchange interaction between the two terminal nickel(II) io     

New octahedral bis-α-diimine nickel(II) complexes containing chloro-substituted aryl groups: Synthesis, characterization and testing as ethylene polymerisation catalysts

Three new 20-electron bis-α-diimine nickel (II) complexes containing chloro-substituted ligands, bis{bis[N,N′-(3-chloro-2-methylphenyl)imino]-1,2-dimethylethane}dibromonickel 2a, bis{bis[N,N′-(3-chloro-2,6-dimethylphenyl)imino]-1,2-dimethylethane}dibromonickel 2b and bis{bis[N,N′-(4-chloro-2,6-dimethyl-phenyl)imino]-1,2-dimethylethane}dibromonickel 2c, were synthesized and characterized. The molecular structure of complex 2a was determined by X-ray crystallography. In the solid state, complex 2a has a pseudo-octahedral geometry about the nickel center, containing two α-diimine ligands in the pseudo-equatorial plane and two trans bromide ligands occupying the axial positions. These complexes, activated by diethylaluminum chloride (DEAC) were tested in the polymerization of ethylene under mild conditions. NMR analysis shows that highly branched polyethylenes are obtained using these bis-α-diimine nickel(II) complexes containing electron-withdrawing Cl groups in the aryl groups (e.g. 84 branches/1000 C, at 20 °C). The catalytic activity, polymer molecular weight and polymer degree of branching were significantly affected by the number of methyl substituents in the ortho-aryl position and the chlorine substituent position in the aryl rings of the coordinated α-diimine ligands.     

Hydrogen-bonded and π-stacked nickel(II) thiosemicarbazone complexes: Synthesis,spectral and structural studies

Transition Metal Chemistry - Mixed ligand Ni(II) complexes were synthesized from triphenylphosphine and S-methyl- or S-ethyl-isothiosemicarbazone ligands derived from...     

Synthesis and characterization of sterically encumbered β-ketoiminate complexes of iron(II) and zinc(II)

The synthesis, structure, and spectroscopic signatures of a series of four-coordinate iron(II) complexes of β-ketoiminates and their zinc(II) analogues are presented. An unusual five-coordinate iron(II) triflate with three oxygen bound protonated β-ketoimines is also synthesized and structurally characterized. Single-crystal X-ray crystallographic analysis reveals that the deprotonated bis(chelate)metal complexes are four-coordinate with various degrees of distortion depending on the degree of steric bulk and the electronics of the metal center. Each of the high-spin iron(II) centers exhibits multiple electronic transitions including ligand π to π*, metal-to-ligand charge transfer, and spin-forbidden d-d bands. The (1)H NMR spectra of the paramagnetic high-spin iron(II) centers are assigned on the basis of chemical shifts, longitudinal relaxation times (T(1)), relative integrations, and substitution of the ligands. The electrochemical studies support variations in the ligand strength. Parallel mode EPR measurements for the isopropyl substituted ligand complex of iron(II) show low-field resonances (g > 9.5) indicative of complex aggregation or crystallite formation. No suitable solvent system or glassing mixture was found to remedy this phenomenon. However, the bulkier diisopropylphenyl substituted ligand exhibits an integer spin signal consistent with an isolated iron(ii) center [S = 2; D = -7.1 ± 0.8 cm(-1); E/D = 0.1]. A tentative molecular orbital diagram is assembled.     

Synthesis, structural characterisation and thermal decomposition studies of some 2,4′-bipyridyl complexes with cobalt(II), nickel(II) and copper(II)

2,4-Bipyridyl (2,4-bipy orL) complexes with cobalt(II), nickel(II) and copper(II) of the formulae M(2,4-bipy)₂(CH₃COO)₂·2H₂O (M(II) = Co, Ni, Cu), Co(2,4-bipy)₂SO₄·3H₂O or Ni(2,4-bipy)₂SO₄·4H₂O have been prepared and their IR and electronic (VIS) spectra are discussed. The thermal behaviour of the obtained compounds has also been studied. The intermediate products of decomposition at different temperatures have been characterized by chemical analysis and X-ray diffraction.We thank dr. A. Malinowska for performing VIS spectra. This work was supported by the KBN project No. PB 0636/P3/93/04.     

Synthesis,electrochemical properties and electro-oxidative polymerization of copper(II) and nickel(II) complexes with N′-benzoylthiourea ligands containing pyrrole groups

The synthesis of four N-benzoylthioureas containing pyrrole groups are described. The electrochemical behaviour of their copper(II) and nickel(II) complexes has been investigated in aprotic solvents by coulometry and by cyclic voltammetry which indicates that the electrochemical oxidation of copper complexes leads to the formation of Cu^II-benzylureate complexes. The oxidative polymerization of nickel complexes on platinum and a glassy carbon electrode, has been carried out in MeCN.The redox properties of the polymeric films formed have been examined by cyclic voltammetry. The films are catalytically active in the electroreduction of oxygen.     

Synthesis of rac-2′-(trimethylsilyl)isovaline: A novel silicon-containing α,α-dialkylated α-amino acid

An efficient, convenient, and reliable multi-step synthesis of rac-2′-(trimethylsilyl)isovaline (rac-3) that uses inexpensive reagents in all steps has been developed, starting from diethyl malonate (overall yield 28%). Compound rac-3 is the first α-ethylated α,α-dialkylated silicon-containing α-amino acid.     

Preparation and characterization of trimethylsilyl-substituted benzimidazole metal complexes and structural characterization of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κ N 3]cobalt(II)

The ligands 1-trimethylsilylmethylbenzimidazole, 5-methyl-1-trimethylsilylmethylbenzimidazole, and 5-nitro-1-trimethylsilylmethylbenzimidazole and their Co(II) and Zn(II) complexes were synthesized and characterized by ¹H-NMR, ¹³C-NMR, and elemental analyses. The crystal structure of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κN ³]cobalt(II) has been determined by single crystal X-ray diffraction.     

Synthesis and catalytic activity of rhodium diene complexes bearing indenyl-type fullerene η-ligand

Rhodium η⁵-complexes bearing an indenyl-type fullerene ligand, Rh[C₆₀(PhCH₂)₂Ph](cod) (2), Rh[C₆₀(PhCH₂)₂Ph](nbd) (3) and Rh(C₇₀Ph₃)(cod) (4), have been synthesized from the corresponding fullerene tri-adducts in 93-96% yields. X-ray crystallographic analysis of 4 indicated that the structure of 4 is similar to that of Rh(Ind)(cod). The rhodium complex 2 catalyzes alkyne trimerization reactions and hydroboration reactions.     

Synthesis,characterization, and reactivity of ruthenium(II) complexes containing η6-arene-η1-pyrazole ligands

New ruthenium(II) complexes containing η⁶-arene-η¹-pyrazole ligands were synthesized and characterized by elemental analysis and spectroscopic methods. In addition, the molecular structure of dichloro-3,5-dimethyl-1-(pentamethylbenzyl)-pyrazole–ruthenium(II), [Ru]L_3b, was determined by X-ray diffraction studies. These complexes were applied in the transfer hydrogenation of acetophenone by isopropanol in the presence of potassium hydroxide. The activities of the catalysts were monitored by NMR.     

Synthesis and characterization of binuclear μ-oxalato nickel(II), copper(II) and zinc(II) complexes with 3,3′-diamino-N-methyl-dipropylamine or trans-1,2-diaminocyclohexane

New binuclear complexes of the type [(Ni(Medpt)NO₃)₂ox] (1) (Medpt=3,3′-diamino-N-methyl-dipropylamine, H₂ox=oxalic acid), [(Ni(dach)₂)₂ox]NO₃·2H₂O (2) (dach=trans-1,2-diaminocyclohexane), [(Cu(Medpt))₂ox]X₂·yH₂O (X=NO₃, y=2 2/3 (3); X=ClO₄, y=0 (4)) and [(Zn(dach)₂)₂ox](ClO₄)₂·2H₂O (5) have been prepared and characterized by IR and UV–Vis spectroscopies. Spectroscopic data are consistent with oxalate-bridged structures between six-coordinated (N₃O₃ or N₄O₂) Ni(II) (compounds 1 or 2), five-coordinated (N₃O₂) Cu(II) (compounds 3 and 4) or six-coordinated (N₄O₂) Zn(II) (compound 5). The crystal structure of [(Cu(Medpt))₂ox](NO₃)₂·2 2/3 H₂O (3) has been determined by single-crystal X-ray analysis. The structure of (3) consists of centrosymmetric binuclear cations [(Medpt)Cu(ox)Cu(Medpt)]²⁺, nitrate anions and water molecules of crystallization. The copper atom is five-coordinated by two oxalate–oxygen and three Medpt–nitrogen atoms, in a hybrid arrangement between trigonal–bipyramidal and square–pyramidal. The temperature dependence of magnetic susceptibility (1.8–300 K) was measured for compounds 1–4. Magnetochemical measurements show that Ni(II) complexes are antiferromagnetically coupled, J=−29.4 (1) and −32.7 cm⁻¹ (2) (H=−JS₁S₂) while the Cu(II) complexes present a very weak coupling, J=−2.6 (3) and +1.9 cm⁻¹ (4), being antiferro- and ferromagnetic in nature.     

Synthesis and crystal structure of complexes of manganese(II), cobalt(II), and nickel(II) isothiocyanates with ?-caprolactam

The possibility of ?-caprolactam (CPL) to coordinate to manganese(II), cobalt(II), and nickel(II) rhodanides has been investigated. New complexes trans-[M(CPL)₄(NCS)₂], where M = Mn (I), Co (II), and Ni (III), have been synthesized. The complexes have been studied by chemical analysis and IR spectroscopy. According to X-ray diffraction, complexes are isostructural to each other and crystallize in monoclinic space group P2₁/c, Z = 2. For I: a = 6.9457(2) ?, b = 17.7751(6) 0A, c = 12.8999(4) 0A, ?? = 104.2670(10)°, V = 1543.51(8) ?³, ??_calc = 1.342 g/cm³, R ₁ = 0.0426. For II: a = 6.8925(2) ?, b = 17.8189(8) ?, c = 12.7278(6) ?, ?? = 104.421(2)°, V = 1513.93(11) ?³, ??_calc = 1.377 g/cm³, R ₁ = 0.0280. For III: a = 6.7804(2) ?, b = 18.4631(4) ?, c = 12.4841(3) ?, ?? = 105.2950(10)°, V = 1507.49(7) ?³, ??_calc = 1.382 g/cm³, R ₁ = 0.0273. Structures I?CIII are molecular; the metal atom in each of them coordinates four CPL molecules and two NCS groups via oxygen and nitrogen atoms, respectively.     

From platina-β-diketones to diacetylplatinum(II) complexes - Synthesis, characterization and structural features

The reaction of the electronically unsaturated platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1a) with N^?N donors led to the formation of diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H)(N^?N)] (2). By the reaction of these complexes with NaOH in a two-phase system (H₂O/CH₂Cl₂) diacetylplatinum(II) complexes [Pt(COMe)₂(N^?N)] (N^?N = bpy, 4a; 4,4′-Me₂-bpy, 4b; 4,4′-t-Bu₂-bpy, 4c; 4,4′-Ph₂-bpy, 4d; 4,4′-t-Bu₂-6-n-Bu-bpy, 4e; bpym, 4f; bpyr, 4g; phen, 4h; 4-Me-phen, 4i; 5-Me-phen, 4j) were obtained. All complexes were characterized by microanalysis, IR and ¹H and ¹³C NMR spectroscopy. Additionally, complexes 4a, 4c, 4d and 4e were characterized by single-crystal X-ray diffraction analysis. The observed variety of packing patterns resulting from π-π stacking and hydrogen bonding is discussed.     

Synthesis,characterization, molecular and supramolecular structures of nickel(II) complexes derived from α-diketone and α-ketoaldehyde bisaroylhydrazones

A new series of nickel(II) complexes derived from symmetrical diacetyl bisaroylhydrazones [Ni(L¹-R)] and unsymmetric phenylglyoxal bisaroylhydrazones [Ni(L²-R)] have been prepared and characterized. X-ray crystal and molecular structures of [Ni(L¹-H)], [Ni(L¹-pCH₃O)] and [Ni(L¹-pNO₂)] have been determined. In these complexes, the Ni(II) is in a distorted square planar environment and the aroylhydrazone acts as dinegative tetradentate ligand forming a 5,5,5-tricyclic chelate ring. Reaction of [Ni(L¹-R)] with aqueous ammonia afforded the paramagnetic five coordinate [Ni(L¹-R)(NH₃)] while [Ni(L²-R)] gave the diamagnetic square planar [Ni(L²-R)(NH₃)] complexes. Reaction of [Ni(L¹-R)] complexes with imidazole gave the corresponding paramagnetic octahedral bis(imidazole) adducts. X-ray structures of both [Ni(L¹-H)(HIm)₂] and [Ni(L¹-pNO₂)(HIm)₂] suggest a distorted octahedral structure where the bisaroylhydrazone occupies the basal plane while the two imidazoles occupy the axial sites. The molecular units are associated together forming triple stranded helical chains. With imidazole the [Ni(L²-R)] series gave the corresponding diamagnetic mono(imidazole) [Ni(L²-R)(HIm)] complexes, The X-ray structure of {Ni(L²-pCH₃)(HIm)] suggest square planar arrangement around the Ni(II) where the bisaroylhydrazone acts as dinegative NNO tridentate ligand forming with the Ni(II) a 5,6-bicyclic chelate ring the fourth coordination site is occupied by imidazole nitrogen.     

Synthesis and spectral characterization of sparteine and α -isosparteine complexes with copper(II) sulfate

Complexes of CuSO₄ of the general formula [Cu(C₁₅H₂₆N₂)SO₄] where [C₁₅H₂₆N₂] is sparteine or α-isosparteine have been obtained from copper(II) and an appropriate alkaloid. The 1?:?1 (metal?:?alkaloid) stoichiometry was confirmed by elemental analysis. The compounds have been characterized by mass spectrometry, IR, and UV–Vis spectroscopy. The magnetic properties were also determined; no anti-ferromagnetic behavior was observed. Information on the geometry of newly obtained compounds was obtained using quantum-chemical calculations.     

Study of novel η-cyclopentadienyl and η-arene platinum group metal complexes containing a N4-type ligand and their structural characterization

The mononuclear η⁵-cyclopentadienyl complexes [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br] and pentamethylcyclopentadienyl complex [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] react in the presence of 1 eq. of the tetradentate N,N′-chelating ligand 3,5-bis(2-pyridyl)pyrazole (bpp-H) and 1 eq. of NH₄PF₆ in methanol to afford the mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(bpp-H)]PF₆ ([1]PF₆), [(η⁵-C₅H₅)Os(PPh₃)(bpp-H)]PF₆ ([2]PF₆) and [(η⁵-C₅Me₅)Ru(PPh₃)(bpp-H)]PF₆ ([3]PF₆), respectively. The dinuclear η⁵-pentamethylcyclopentadienyl complexes [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Ir(μ-Cl)Cl]₂ as well as the dinuclear η⁶-arene ruthenium complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂ and [(η⁶-p-ⁱPrC₆H₄Me)Ru(μ-Cl)Cl]₂ react with 2 eq. of bpp-H in the presence of NH₄PF₆ or NH₄BF₄ to afford the corresponding mononuclear complexes [(η⁵-C₅Me₅)Rh(bpp-H)Cl]PF₆ ([4]PF₆), [(η⁵-C₅Me₅)Ir(bpp-H)Cl]PF₆ ([5]PF₆), [(η⁶-C₆H₆)Ru(bpp-H)Cl]BF₄ ([6]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)Ru(bpp-H)Cl]BF₄ ([7]BF₄). However, in the presence of 1 eq. of bpp-H and NH₄BF₄ the reaction with the same η⁶-arene ruthenium complexes affords the dinuclear salts [(η⁶-C₆H₆)₂Ru₂(bpp)Cl₂]BF₄ ([8]BF₄) and [(η⁶-p-ⁱPrC₆H₄Me)₂Ru₂(bpp)Cl₂]BF₄ ([9]BF₄), respectively. These compounds have been characterized by IR, NMR and mass spectrometry, as well as by elemental analysis. The molecular structures of [1]PF₆, [5]PF₆ and [8]BF₄ have been established by single crystal X-ray diffraction studies and some representative complexes have been studied by UV–vis spectroscopy.     

Synthesis and characterisation of bite angle-dependent (η1-allyl)Rh and (η3-allyl)Rh complexes bearing diphosphine ligands. Implications for nucleophilic substitution reactions

Several novel rhodium allyl complexes have been prepared and their structures have been studied using NMR spectroscopy and X-ray crystallography. Depending on the bite angle of the ligand and the substitution pattern of the allyl group, two different coordination modes (η¹ and η³) have been observed for the allyl moiety. The activities of these Rh allyl complexes in the allylic alkylation reaction have been tested. We have shown that both coordination modes give active complexes in this reaction, but that the regioselectivity is dependent on the coordination mode of the allyl group.     

Synthesis,characterization and biological studies on unsymmetrical Schiff-base complexes of nickel(II), copper(II) and zinc(II) and adducts with 2,2′-dipyridine and 1,10-phenanthroline

A series of metal(II) unsymmetrical Schiff-base complexes, {M(C₁₀H₆OCH:N(CH₂)₂N?:?C(CH₃)CH?:?C(CH₃)O), where M=Ni(II), Cu(II) and Zn(II)}, and their 2,2′-dipyridine (bipy) and 1,10-phenanthroline (phen) adducts are synthesized and characterized by microanalysis, magnetic susceptibility, conductance, IR and UV-Vis spectra. The ligand coordinates using the N₂O₂ chromophore to give a two-metal-center four-coordinate square-planar geometry. IR and UV-Vis spectra are consistent with octahedral adducts. The compounds are non-electrolytes in nitromethane and magnetic moments indicate that the complexes are magnetically dilute. The antimicrobial activity of the compounds against ten bacteria and one fungus are reported. The Cu(II) and Zn(II) complexes showed good activity against many of the organisms while their adducts are generally not sensitive. The minimum inhibitory concentrations (MICs) of the sensitive compounds are between 3.0–13.0?mg?mL^?1.