Dimerization of vinylcyclopropane and its codimerization with 1,3-dienes catalyzed by cobalt complexes

Conclusions The dimerization of vinylcyclopropane to 2-cyclopropyl-1,5(Z)-heptadiene and the codimerization of vinylcyclopropane with 1,3-dienes (butadiene, isoprene, and 2-cyclopropylbutadiene) with the formation of 2-cyclopropyl-1,4-hexadienes were carried out in the presence of the catalytic systems Co(acac)₃-1,2-bis(diphenylphosphino)ethane [1,2-bis(diphenylphosphino)methane]-AlEt₂Cl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1356–1360, June, 1988.     

1,3-butadiene telomerization with methanol catalyzed by heterogenized palladium complexes

The heterogenization of palladium complexes on silica as well as on functionalized styrene/divinylbenzene crosslinked resins and linear poly(styrene) is described. In particular, palladium (0) and palladium (II) derivatives were anchored to the above polymeric systems through their functionalization with bidentate ligands such as acetylacetonate and 1,3-bis(diphenylphosphino)propane moieties. The resulting heterogenized complexes were checked in the catalytic telomerization of 1,3-butadiene with methanol. Their performances were studied in terms of activity and selectivity to telomers. Whereas the heterogenization of palladium complexes either on silica or on polymer resins via the acetylacetonate ligand resulted labile during the catalytic cycle, the polymer-bound palladium complexes via the diphosphine ligand, when activated by an alkoxide, displayed activity and selectivity comparable with those of the corresponding homogeneous counterparts, without appreciable metal leaching in solution.     

Highly active and stereospecific polymerization of 1,3-butadiene catalyzed by dinuclear cobalt(II) complexes bearing 3-aryliminomethyl-2-hydroxybenzaldehydes

A series of cobalt(II) complexes bearing 3-aryliminomethyl-2-hydroxybenzaldehydes (tridentate [NOO] ligands) was prepared and characterized by FT-IR and elemental analysis along with single-crystal X-ray diffraction. The X-ray diffraction analysis revealed that a dinuclear centrosymmetrical structure formed, in which each cobalt atom is surrounded by two bridged ligands and two acetate groups as a distorted octahedron. These dinuclear cobalt complexes displayed high catalytic activities for the polymerization of 1,3-butdiene on activation with organoaluminum cocatalysts to yield cis-1,4-polybutadiene with high selectivity. Ethylaluminum sesquichloride (EASC) was found to be the most efficient cocatalyst resulting in high conversion of butadiene and cis-1,4 content in the polymers with moderate molecular weight. The high catalytic activity and stereoselectivity could be achieved in a wide range of reaction conditions. All the dinuclear cobalt complexes (C1-C6) yielded predominantly cis-1,4-polybutadienes (> 96%) with negligible amounts of trans-1,4 (< 2.4%) and 1,2-vinyl (< 1.5%) products under the Al/Co molar ratio of 80 at 25 °C. The ligand modification by varying the substituents at the 4-position of phenol and on the imino-N aryl ring showed slight influence on the catalytic activity and microstructure of the resulting polymers.     

Polymerization of 1,3-Butadiene Catalyzed by Cobalt(Ⅱ) and Nickel(Ⅱ) Complexes Bearing Pyridine-2-imidate Ligands

Cobalt and nickel complexes (1a-1d and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element analysis, and complex 1a was further characterized by single-crystal X-ray diffraction. The solid state structure of complex 1a displayed a distorted tetrahedral geometry. Upon activation with ethylaluminum sesquichloride (EASC), all the complexes showed high activities toward 1,3-butadiene polymerization. The cobalt complexes produced polymers with high cis-1,4 contents and high molecular weights, while the nickel complexes displayed low cis-1,4 selectivity and the resulting polymers had low molecular weights. The catalytic activities of the complexes highly depended on the ligand structure. With the increment of polymerization temperature, the cis-1,4 content and the molecular weight of the resulting polymer decreased.     

Reductive desymmetrization of 2-alkyl-1,3-diketones catalyzed by optically active beta-ketoiminato cobalt complexes

[reaction: see text] The reductive desymmetrization of acyclic 1,3-diketones was achieved for the first time by catalytic borohydride reduction in the presence of optically active beta-ketoiminato cobalt(II) complex catalysts. In this reaction, various 2-substituted-1,3-diaryl-1,3-propanediones were converted into the corresponding optically active 2-substituted-1,3-diaryl-3-hydroxypropanone in good-to-high yields with excellent diastereo- and enantioselectivities and high catalytic efficiencies.     

α-二亚胺钴配合物催化1,3-丁二烯高活性与高顺式-1,4选择性聚合

合成了一系列α-二亚胺钴配合物[ArN=C(Me)-(Me)C=NAr]CoCl₂(Ar=C₆H₅, 3a; 4-MeC₆H₄, 3b; 4-MeOC₆H₄, 3c; 4-FC₆H₄, 3d; 4-ClC₆H₄, 3e; 2-MeC₆H₄, 3f; 2-EtC₆H₄, 3g; 2-ⁱPrC₆H₄, 3h; 2,4,6-Me₃C₆H₂, 3i; 2,6-Et₂C₆H₃, 3j; 2,6-ⁱPrC₆H₃, 3k)和作为对比的吡啶双亚胺二氯化钴配合物(4a), 并用X射线单晶衍射方法研究了配合物3i, 3k和4a的分子结构. α-二亚胺钴配合物在倍半乙基氯化铝的作用下对丁二烯聚合有较高的催化活性,得到的顺式-1,4结构含量达98%,且有较高分子量(M_n≈1×10⁴-1×10⁵)的聚丁二烯. 配体的电子效应影响催化剂的活性及顺式-1,4选择性, 而配体的空间位阻对丁二烯聚合几乎没有影响. 详细研究了聚合时间、聚合温度、烷基铝助催化剂及铝比等条件对丁二烯聚合行为的影响.     

Loss of methyl from ionized 2-hydroxy-1,3-butadiene

The loss of methyl from unstable, metastable and collisionally activated [CH₂?CH? C(OH)?CH₂]⁺˙ ions (1⁺˙) was examined by means of deuterium and ¹³C labelling, appearance energy measurements and product identification. High-energy, short-lived 1⁺˙ lose methyl groups incorporating the original enolic methene (C(1)) and the hydroxyl hydrogen atom (H(0)). The eliminations of C(1)H(1)H(1)H(4) and C(4)H(4)H(4)H(0) are less frequent in high-energy ions. Metastable 1⁺˙ eliminate mainly C(1)H(1)H(1)H(4), the elimination being accompanied by incomplete randomization of the five carbon-bound hydrogen atoms. The resulting [C₃H₃O]⁺ ions have been identified as the most stable CH₂?CH? CO⁺ species. The appearance energy for the loss of methyl from 1 was measured as AE[C₃H₃O]⁺ = 10.47 ± 0.05 eV. The critical energy for 1⁺˙ → [C₃H₃O]⁺ + CH₃˙ is assessed as E_c ? 173 kJ mol^?1. Reaction mechanisms are proposed and discussed.     

Syntheses and structures of the cobalt, nickel, and zinc complexes with 1,4-diaza-1,3-butadiene ligands

Several cobalt(II), nickel(II), and zinc(II) complexes with a series of ligands of the 1,4-diaza-1,3-butadiene type bearing aryl (2,6-di-iso-propylphenyl, mesityl) and alkyl (tert-butyl, iso-propyl) substituents at the nitrogen atoms are synthesized. The obtained complexes are characterized by X-ray structure analysis, IR spectroscopy, and elemental analysis.     

Codimerization of 2-cyclopropyl-1,3-butadikne with ethylene

Conclusions The codimerization of 2-cyclopropylbutadiene with ethylene by the action of low-valence cobalt complexes was studied. The major reaction product in the presence of the Co(acac)₂-Ph₂ PCH₂CH₂PPh₂-Et₂AlCl catalytic system is E-4-cyclopropyl-1,4-hexadiene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1196–1198, May, 1986.The authors express their gratitude to L. M. Khalilov for interpretation of the¹³C NMR spectrum.     

Polymerization of 1,3-butadiene on cobalt and nickel halides

Butadiene polymerizes to cis-1,4 polymer on irregularly stacked, halogen-deficient crystals of cobalt(II) or nickel(II) halides. Halogen is removed from the halides by heating the salts under high vacuum or by photolyzing them in the presence of butadiene. Intrinsic viscosity and solubility of the polymer reach a steady state during polymerization. Cobalt chloride produces polymer of higher intrinsic viscosity than nickel chloride, but polymerization on nickel chloride is faster. Catalytic activity is attributed to the presence of ≤0.1% of nickel and cobalt monohalides in the catalyst.     

Cooligomerization of 1,2-dienes with norbornadienes catalyzed by cobalt complexes

Conclusions Under the action of low-valency cobalt complexes [2 + 2 + 2] cycloaddition of allene, cyclopropylallene, phenylallene, and 1,2-cyclononadiene to norbornadiene and spirocyclo-[2.2.l]hepta-2,5-diene-7,1-cyclopropane takes place with the formation of derivatives of tetracyclo[4.3.0.0^2,4. 1.0^3,7] nonane in high yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1346–1356, June, 1988.