Olefinic substitution reaction catalyzed by sulfur-containing polymeric palladium complexes

Silica-supported sulfur-containing polymeric palladium complexes were synthesized by the coordination of sulfur-containing polymeric ligands with palladium acetate or palladium chloride. The activated alkenes were reacted selectively with iodobenzene in the presence of tertiary amines and polymeric palladium complexes containing sulfur to give phenyl-substituted derivatives. High yields can be obtained under appropriate conditions with a low catalyst concentration. The sulfur-containing polymeric palladium complexes showed higher activities and better selectivities and stabilities than the corresponding phosphine-containing systems.     

Koordinationsverbindungen des 2-Hydroxy-4,6-diphenyl-thiobenzophenons. Chelat-Komplexe des Cobalts und Nickels,Röntgenkristallstrukturanalyse der Nickelverbindung

Coordination Compounds of 2-Hydroxy-4,6-diphenyl-thiobenzophenone. Chelate Complexes of Cobalt and Nickel, X-ray Structure of the Nickel Compound 2-Hydroxy-4,6-diphenyl-thiobenzophenone (HL) reacts under deprotonation with metal salts to chelate complexes. The reactions with nickel acetate or cobalt acetate yield neutral complexes of the composition NiL₂ and CoL₃, respectively. The nickel compound crystallizes monoclinic in the space group P2₁/c (No. 14), a = 17.55(6), b = 26.69(4), c = 8.49(9) Å, β = 102.7(2)°, Z = 4. The nickel atom has a distorted squareplanar coordination sphere. The ligands are cis coordinated.     

Ring opening reactions of pyromellitic dianhydride for the synthesis of first row transition metal dicarboxylate complexes

The ring opening reaction of pyromellitic dianhydride by methanol is an effective method to prepare first row transition metal dicarboxylate complexes. The reactions of different first row transition metal salts with pyromellitic dianhydride in the presence of nitrogen donating bidentate ligands such as 1,10-phenanthroline and 2,2′-bipyridine gives different compositions depending on the ligand and the metal salts used. For example, the reaction of nickel(II) acetate with pyromellitic dianhydride in the presence of 1,10-phenanthroline results in the formation of a carboxylato bridged nickel(II) metallacycle through the ring opening reaction of pyromellitic dianhydride (PAH) at the 1 and 3-positions, whereas a mononuclear tetra-aqua 2,2′-bipyridine nickel(II) complex is formed in a similar reaction of nickel(II) acetate through ring opening at the 1,4-position of PAH. Mononuclear cobalt(II) dicarboxylate complexes are formed from the ring opening reaction of pyromellitic dianhydride in methanol in the presence of the nitrogen donor ligands 1,10-phenanthroline or 2,2′-bipyridine. Copper(II) chloride on reaction with PAH and 2,2′-bipyridine gives a mononuclear complex via ring opening at the 1 and 4-positions; having chlorides inside and outside the coordination sphere. Whereas, the reaction of copper(II)acetate gives dinuclear copper complexes having a monodentate carboxylato bridge arising from the carboxylato groups at the 1 and 4-positions on the aromatic ring. The crystal structures of all the complexes have been determined.     

New Cu(II), Co(II), and Ni(II) complexes with thieno[2,3-b]pyridine and 2-methylthieno[2,3-b]pyridine as ligands: Synthesis and crystal structures

Although thienopyridines attract attention because of their biological activities, they have not been used as ligands in coordination compounds. Thieno[2,3-b]pyridine was prepared by known procedures; by reduction of 2-nitrothiophene, and reaction of the resulting 2-thienyl ammonium salt with malondialdehyde tetramethylacetal in the presence of zinc chloride. The same procedure was used for the preparation of a new derivative, 2-methylthieno[2,3-b]pyridine, starting from 2-methyl-5-nitrothiophene. The thienopyridines were used in the synthesis of coordination compounds. Chlorides, isothiocyanates, acetates, and chloroacetates of copper(II), nickel(II), or cobalt(II) were used as starting salts. The prepared complexes were characterized by elemental analysis and FT IR. Structures of the four complexes were determined by single-crystal X-ray diffraction analysis. Presented at the 1st International Conference “Applied Natural Sciences” on the occasion of the 10th anniversary of the University of Ss. Cyril and Methodius, Trnava, 7–9 November 2007.     

Multi-functional coordination crosslinks in poly(vinylamine) complexes with cobalt chloride

Poly(vinylamme) complexes with cobalt chloride hexahydrate exhibit the largest glass transition temperature enhancements that have been measured in this laboratory. T_g increases from 56°C in the undiluted polymer to 193°C when the molar concentration of cobalt is only 3%, based on the moles of polymeric repeat units. This translates to a 45°C enhancement in T_g per mol% cobalt. Higher glass transition temperatures have been measured for other polymeric complexes with d-block salts, but this study reports the largest ΔT_g=T_g(complex)-T_g(undiluted polymer) when transition-metal catalyzed chemical crosslinking reactions do not occur. A plausible explanation for this effect is based on the fact that cobalt chloride hexahydrate maintains pseudo-octahedral symmetry in the undiluted crystalline state and in an amorphous glassy complex with the polymer. The lone pair on nitrogen in the amino sidegroup is a strong base and, most likely, displaces all four waters of hydration that coordinate directly to the metal center. In fact, estimates of the ligand field splitting and the ligand field stabilization energy for octahedral cobalt complexes that contain methyl amine (CH₃NH₂) model ligands suggest that five or six amino sidegroups from several different chains might coordinate to each metal center, drastically reducing the mobility of the polymer. Both chloride anions remain near each divalent Co²⁺ center, but either one or two Cl⁻ might not reside in the first-shell coordination sphere of the transition metal. This bonding picture suggests that octahedral cobalt acts as a multi-functional bridge between five or six amino sidegroups. Empirical ligand field stabilization calculations support the concept that octahedral Co²⁺ is a multi-functional coordination crosslinking agent, and the inorganic literature provides experimental verification that similar small-molecule complexes (i.e., [Co(NH₃)₆]²⁺) exist. It is proposed that the onset of T_g occurs when sufficient thermal energy is supplied to remove either x or (x-1) amino sidegroup ligands from the coordination sphere of cobalt, where x is either 5 or 6. This is an endothermic process based on bond energies, as well as calculations which focus on the relative energies of the metal d-electrons.     

Hydrolytic ring opening reactions of anhydrides for first row transition metal dicarboxylate complexes

Ring opening reactions of 2,3-pyridine dicarboxylic anhydride are studied with hydrated salts of cobalt, nickel and zinc. The hydrated metal salts preferentially hydrolyze 2,3-pyridine dicarboxylic anhydride rather than causing esterification in methanol medium. Hydrolytic opening of 2,3-pyridine dicarboxylic anhydride by hydrated cobalt(II) acetate and nickel(II) acetate resulted in the corresponding chelate complexes of monodeprotonated 2,3-pyridine dicarboxylic acid. The reaction of copper acetate with pyromellitic dianhydride in the presence of 1,10-phenanthroline gives a dinuclear copper complex whereas a similar reaction with copper(II) chloride gives a mononuclear copper complex.     

Transition metal complexes of N-picolyl polyurethane

N-Picolyl polyurethanes (PUPY) were synthesized by nucleophilic substitution. The blends of these polyurethanes with various of transition metal chlorides [cobalt(II), nickel(II), and copper(II)] were studied by spectroscopic and thermal analysis. Ultraviolet-visible and infrared spectroscopic evidence indicates that a tetrahedral cobalt(II) complex with two pendent picolyl groups in the first-shell coordination sphere of Co²⁺ is formed in a series of blends with different molar ratio (from 10/1 to 2/1) of picolyl groups to cobalt(II) ions. According to the result of Small-Angle X-ray Scattering (SAXS), Differential Scanning Calorimetry (DSC), and Dynamic Mechanical Thermal Analysis (DMTA), coordination interaction between ligands in hard segments and metal ions provides a driving force for phase separation. The coordination strength of pyridine with Ni²⁺ is stronger than Co²⁺ and Cu²⁺. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1539–1546, 1998     

Solid-state polymerization of vinylpyridine coordination compounds

A survey of the solid-state polymerizability of 2- and 4-vinylpyridine (Vpy) complexes of divalent cobalt, nickel, copper, and zinc chlorides has been carried out. The influence of metal ion, ligand, coordination stereochemistry, and crystal structure is discussed. The tetrahedral modification of the complex Co(4-Vpy)₂Cl₂ has been found to undergo a particularly facile thermal polymerization below its melting point to yield high molecular weight poly-4-vinylpyridine. The polymer is shown to be conventional atactic head-to-tail poly-4-vinylpyridine. Thermogravimetric methods and optical microscopy have been used to study the thermal polymerization of single crystals of the complex. Results indicate a diffusion-controlled mechanism in which defective regions in the crystal act as nuclei for the polymerization.     

Synthesis, structure and spectroscopy of new thiopyrone and hydroxypyridinethione transition-metal complexes

The coordination chemistry of several O,S mixed donor ligands, namely thiopyrone and hydroxypyridinethione chelators, with a variety of middle and late first-row transition-metal ions is described. Complexes of 3-hydroxy-2-methyl-4-thiopyrone (thiomaltol) with cobalt(II), copper(II) and zinc(II); 3-hydroxy-1,2-dimethyl-4(1H)-pyridinethione (3,4-HOPTO) with iron(III), nickel(II), copper(II) and zinc(II); and 3-hydroxy-1-methyl-2(1H)-pyridinethione (3,2-HOPTO) with iron(III), nickel(II), copper(II) and zinc(II) have been synthesized and characterized. The structures, absorbance spectroscopy, cyclic voltammetry and superconducting quantum interferometer device (SQUID) measurements of selected metal complexes, as well as ligand protonation constants, are reported. Most of the metal complexes show coordination geometries indicative of a strong trans influence by the O,S chelators. The data presented herein provide the most detailed study of the transition-metal coordination chemistry of both thiopyrone and hydroxypyridinethione O,S donor ligands to date, and provide the basis for the investigation of these ligands in realm of biological inorganic chemistry.     

Synthesis of poly-yne polymers containing transition metals,disilane, disiloxane and phosphine groups in the main chain

The synthesis and characterization of metal poly-yne polymers containing disilane, disiloxane and phosphine groups in the main chain are described. The platinum and palladium poly-yne polymers were synthesized by polycondensation reactions between a metal chloride and an α, ω-bisethynyl complex in amines in the presence of cuprous iodide as a catalyst. The nickel poly-yne polymers were synthesized by an alkynyl ligand exchange reaction between a nickel acetylide and an α, ω-bisethynyl complex in diethylamine in the presence of cuprous iodide as a catalyst. The reaction of the platinum poly-yne polymer, containing disiloxane groups in the main chain, with copper (I) salts afforded adducts of η-²-bonded σ-acetylide polymer complexes. The reactions of the palladium poly-yne polymer, containing phosphine groups in the main chain, with transition-metal carbonyl complexes afforded polymer complexes which have phosphorus in the main chain-transition-metal bonds. A concentrated solution of the platinum poly-yne polymer containing disiloxane groups in the main chain forms a lyotropic liquid crystal in dichloromethane or 1, 2-dichloroethane.     

Calorimetric study of cesium hexafluoroarsenate CsAsF<Subscript>6</Subscript> at elevated temperatures

Summary Cobalt(II), nickel(II) and copper(II) complexes of some aroylhydrazone Schiff’s bases derived from isoniazide (hydrazide of isonicotinic acid) with p-hydroxybenzaldehyde; 2,4-dihydroxybenzaldehyde or 2-hydroxy-1-naphthaldehyde are prepared and characterized. The study reveals that the ligands coordinate in the keto form. That transformed to the enol through the loss of HCl upon heating the solid complexes. The copper(II) complexes are thermochromic in the solid-state while the cobalt(II) complex, 3 of 2,4-dihydroxybenzaldehyde moiety is solvatochromic in hot DMF. The chromisms obtained were discussed in terms of change in the ligand field strength and/or coordination geometry.     

Formation constants for the complexes of levulinate and acetate with manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and hydrogen ions

Formation constants are reported for the levulinate complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) at 25 degrees in 0.1M chloride medium. In addition, results are presented for the corresponding acetate complexes for comparison. Protonation constants for the two ligands are also reported.     

Metallic film formation using direct micropatterning with photoreactive metal complexes

Palladium, cobalt, and nickel in complex with photoacid-generating ligands, 4-(2-nitrobenzyloxycarbonyl)catechol and 4-(6-nitroveratryloxycarbonyl)catechol, were prepared in solution. Films formed from the metal complex solutions perform as positive-tone, directly photopatternable palladium, cobalt, nickel oxide, or composite film precursors. After exposure, acid-bearing selectively soluble complexes could be removed to give patterned films upon developing in aqueous base, which were transformable to the corresponding pattern-preserving metal/metal oxide film. The photodynamics of photoinduced solubility and direct micropatterning of palladium, cobalt, nickel, and palladium/nickel oxide composite films were investigated. Employing palladium as the initiator for autocatalytic chemical plating, selective direct copper plating on palladium film on polyethylene naphthalate and palladium/nickel oxide composite film on glass was accomplished.     

Aggregation behaviour below the gelation threshold for metal-olefin coordination in diene polymers

This study focuses on aggregation below the gelation threshold in ternary solutions containing diene polymers, atactic 1,2-polybutadiene (PBu) or 3,4-polyisoprene (PI), and an inorganic salt, bis(acetonitrile) dichloropalladium(II). Upon mixing, effective coordination crosslinks are formed because the acetonitrile ligands of the palladium salt are displaced by olefinic pendant groups of the polymers. In all cases, the aggregation kinetics correlate with PdCl₂ concentration because the polymer concentration is 100 times greater than the salt concentration. Aggregation is the process that occurs prior to gelation as the transition-metal salt forms a coordination bridge between two different polymer chains. Differential analysis of the initial aggregation rate on the basis of light scattering data at 45° relative to the incident throughput beam reveals that the ‘true’ order of the coordination reaction is close to unity. This suggests that coordination crosslinking is diffusion-controlled in the early stages of aggregation. Half-life analysis of viscous solutions yields an overall reaction order of 1.6 for aggregation of polybutadiene and palladium chloride in tetrahydorfuran (THF). Scaling analysis of the weight-average molecular weight dependence of the root-mean-square size of isolated scattering particles yields an effective exponent of 0.7 for polymer/metal-salt complexes at infinite dilution. This experimental scaling law agrees with literature values for cross-linked polymer networks. In all cases, the size of the aggregates increases at higher PdCl₂ concentration. For polybutadiene/PdCl₂ mixtures in THF or toluene below the gelation threshold, the light-scattering-detected average aggregation number (AN = M_{w, complex}/M_{w, pure polymer} via Zimm-plot intercepts) for low-viscosity solutions is 2, while AN ∼ 9 for viscous THF solutions. In contrast, low aggregation numbers (AN ∼ 2) were calculated for viscous ternary mixtures of 3,4-polyisoprene and PdCl₂ in THF.     

Synthesis and characterization of new ketooximes and their complexes

The starting point of the research was the reaction of chloroacetyl chloride with biphenyl in the presence of aluminum chloride. 4-Biphenylhydroximoyl chloride (HL) was obtained by reacting synthesized 4-(chloroacetyl)biphenyl with alkyl nitride. Four new substituted 4-(alkylaminoisonitrosoacetyl)biphenyles (ketooximes) were prepared by reacting 4-biphenylhydroximoyl chloride with corresponding amines in EtOH. The following amines were used for ligands: p-toluidine, p-chloroaniline, pyrrolidine, and 4-aminoacetophenone. Mononuclear complexes with a metal-ligand ratio of 1: 2 were prepared using cadmium(II), cobalt(II), copper(II), nickel(II), lead(II), and zinc(II) salts. These compounds have been characterized by elemental analyses, AAS, infrared spectra and magnetic susceptibility measurements. The ligands have been further characterized by ¹H NMR. The results suggest that the ketooximes act as bidentate ligands which bond metal ions through the oxime and carbonyl oxygen. The text was submitted by the authors in English.     

Hydrosoluble transition-metal coordination compounds of triphenylphosphine m-trisulfonate

By using ³¹P NMR and IR techniques it is established that the basicities of triphenylphosphine m-trisulfonate (TPPTS) and triphenylphosphine (PPh₃) are in the same order of magnitude. This highly hydrosoluble phosphine is a convenient ligand for the synthesis of hydrosoluble coordination compounds of molybdenum(0), palladium(II), platinum(II) and rhodium(I). The exchange of TPPTS with ligands other than PPh₃ (nitriles, carbon monoxide, olefins, chloride) can be used to obtain the desired complexes. However, because redox reactions between metal salts, water and TPPTS are possible, the synthesis of lowvalent precursors must be carried out and the experimental conditions have to be carefully controlled to avoid side-reactions and the participation of the sulfonate anions in competitive reactions.     

Molekülstruktur und intermolekulare Koordination von acylsubstituierten Chelatkomplexen Schiffscher Basen

Molecular Structure and Intermolecular Coordination of Acyl Substituted Schiff Base Complexes The crystal and molecular structures of four Schiff base complexes with additional acyl groups on the meso positions of the ligands were investigated by means of X-ray analysis. In the nickel complex 5 and in the copper complex 4 a the oxygen of the acetyl groups is coordinated within the six membered chelate rings whereas the benzoyl groups act as meso substituents. In contrast to the nickel complex 5 and to the copper complexes 4 b and 6 a which do not show any intermolecular coordination of the free carbonyl groups, 4 a forms 1 D-coordination polymers with strongly distorted octahedral coordination of the copper by intermolecular side-on coordination of both of the benzoyl groups. The linkage of the molecules is markedly different from that in the cobalt complex 3 b where only one of the meso acyl groups is coordinated to give stair-like chains with coordination number 5 of the cobalt and a shorter axial metal-O_axial distance. The central [Cu₄O₄]-unit in 6 a has a cyclooctane-like boat conformation with square-pyramidal coordinated copper instead of the cubane structure with trigonal-bipyramidal coordination in the solvent free α-form of 6 b .     

1,2-polybutadiene complexes with d8 pseudo-square-planar transition-metal salts based on nickel(II), palladium(II), and platinum(II)

The effects of four d⁸ transition-metal complexes from Group 10 on the thermal, mechanical, optical, and spectroscopic properties of atactic 1,2-polybutadiene are compared, in addition to their ability to induce gelation. Olefin coordination and subsequent metal-catalyzed chemical crosslinking occur much more quickly, and to a greater extent, at ambient temperature with PdCl₂(CH₃CN)₂ than with PtCl₂(C₆H₅CN)₂. Alkene side groups in the polymer attack the pseudo-square-planar metal center (i.e., Pd²⁺ or Pt²⁺) from above or below the plane of the coordinatively unsaturated low-molecular-weight organometallic complex and displace neutral acetonitrile or benzonitrile ligands via an associative mechanism. Gelation occurs much more quickly with Pd²⁺ than with Pt²⁺, and the ambient-temperature elastic modulus of solid polybutadiene/palladium complexes increases significantly, without high-temperature annealing, so that a weak rubbery polymer is transformed into a glass via 3 mol % Pd²⁺. Alkene functional groups in the side chain of the polymer do not coordinate to bis(dimethyl)glyoximatonickel(II) at ambient temperature because (1) it is difficult to displace anionic dimethylgloxime ligands that are bidentate; (2) these planar nickel complexes with C_2h symmetry are stacked along the c axis via interlocking methyl groups on adjacent molecules; and (3) there is a lack of π back-bonding between d_xy on Ni(II) and empty π* antibonding orbitals of CC, which typically stabilizes olefin complexes with pseudo-square-planar d⁸ metal centers. Pseudo-octahedral nickel(II) chloride hexahydrate does not form a complex with the polymer, in agreement with some macroscopic properties of these materials. The observed trend in the transition-metal-modified properties of atactic 1,2-polybutadiene in the solid state and in the gel state is Pd(II) > Pt(II) ≫ Ni(II). © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2270–2285, 2004     

Preparation, structure and ethylene polymerization behavior of mixed-halide nickel(II) complexes and cobalt(II) complex containing imidazolium

Preparation of two imidazolium salts, two monomeric nickel(II) and one cobalt(II) complexes bearing imidazolium ligands is described, The solid-state structures of these compounds have determined by single-crystal X-ray diffraction. After activation with methylaluminoxane (MAO) the nickel complexes show moderate catalytic activities of up to 6 × 10⁵ g PE mol⁻¹Ni h⁻¹ for polymerization of ethylene. Catalytic activities, molecular weights have been investigated under the various reaction conditions.     

Preparation of cobalt and nickel complexes of 8-hydroxyquinoline with nanobelt structure via one-step,low-heating,solid-state reactions

Two nano-structural complexes, bis-(8-hydroxyquinoline) cobalt and bis-(8-hydroxyquinoline) nickel, have been prepared by one-step, low-heating, solid-state reaction, a simple, safe, economical and environmentally-friendly method. TEM and SEM images show that the complexes are composed of nanobelts with width ranging from 100 to 300?nm and a length of up to 1?µm. The technique offers a new way for fabricating coordination compounds with one-dimensional nanostructure.