Reactions of ethyl(acetylacetonato)- (triphenylphosphine)nickel(II)- a new hydride nickel complex, (Ph3P)3Ni(H)Br

The reactions of EtNi(PPh₃)(acac) with various reagents have been discussed; the reaction with NaFe(CO)₂Cp or Fe(CO)₅ occurs via nickel(II) reductive carbonylation while EtNi(PPh₃)(acac) and Et₂AlCl afford the unstable EtNi(PPh₃)₂-Cl. The cleavage of the NiC bond with evolution of ethylene and ethane is observed when EtNi(PPh₃)(acac) reacts with CS₂, HgCl₂ and Et₂AlBr. A new nickel hydride complex, (Ph₃P)₃Ni(H)Br, has been obtained from EtNi(PPh₃)-(acac) and Et₂AlBr and its properties have been studied. Another method of synthesis of this hydride complex directly from Ni(acac)₂ and Et₂AlBr has been proposed.     

Interaction of terbium acetylacetonate with diethylaluminum chloride

The interaction of terbium acetylacetonate Tb(acac)₃ · H₂O with Et₂AlCl in toluene was studied by spectroscopic techniques (photoluminescence, IR, and UV-visible spectroscopy) with the use of GLC, volumetric, and chemical analysis.     

Alternating cooligomerization of isoprene and propylene with vanadium catalyst

Alternating cooligomerization of isoprene with propylene has been investigated between ?30 and 0°C, VO(acac)₂–Et₃Al–Et₂AlCl being used as catalyst. In the presence of an excess of propylene, 2,4,7-trimethyl-1,4-octadiene and 2,4-dimethyl-1,4-nonadiene are selectively formed. The formation is explained by the alternating coordination of isoprene and propylene to the vanadium. When triphenylphosphine or pyridine is added to the catalyst, the cooligomerization is suppressed while the formation of the dimer and trimer of isoprene is high.     

Alternating copolymerization of 1- and 2-vinylnaphthalene with methyl methacrylate by using diethylaluminum chloride

The alternating copolymerization of 1- and 2-vinylnaphthalene (1-VNap and 2-VNap) with methyl methacrylate (MMA) by using diethylaluminum chloride (Et₂AlCl) in toluene at 0°C has been studied. No polymerization could occur without Et₂AlCl, and alternating copolymers were obtained only when an equimolar amount of Et₂AlCl with MMA was supplied. Through ¹H-NMR analyses on both dyad and triad of alternating deuterated 1- and 2-α-d-VNap–MMA copolymers, each configuration could be described successfully by a single parameter, coisotacticity σ, whose value was estimated as 0.41 for the former and 0.56 for the latter copolymer, respectively. A rather low coisotacticity of copoly(1-VNap–MMA) was explained in the terms of steric effect (peri effect) of 1-VNap monomer.     

Alternating copolymer of butadiene and propylene. III

Alternating copolymerizations of butadiene with propylene and other olefins were investigated by using VO(acac)₂–Et₃Al–Et₂AlCl system as catalyst. Butadiene–propylene copolymer with high degree of alternation was prepared with a monomer feed ratio (propylene/butadiene) of 4. Alternating copolymers of butadiene and other terminal olefins such as butene-1, pentene-1, dodecene-1, and octadiene-1,7 were also obtained. However, the butadiene–butene-2 copolymerization did not yield an alternating copolymer but a trans-1,4-polybutadiene.     

Nickel‐Catalyzed Homoallylation of Aldehydes and Ketones with 1,3‐Dienes and Complementary Promotion by Diethylzinc or Triethylborane

Regio‐ and stereoselective homoallylation of saturated aldehydes and ketones to give bishomoallyl alcohols 1,3‐anti‐ 1 is achieved with [Ni(acac)₂] (cat.) and Et₂Zn [Eq. (a)]. This new catalyst system thus complements the previously reported combination of [Ni(acac)₂] with Et₃B, which offers advantages in the homoallylation of unsaturated and aromatic aldehydes. acac=acetylacetonato.     

CIDNP study of the Ni(acac)2-catalyzed reaction of triethylaluminum with chloroform

CIDNP effects were found in the Ni(acac)₂-catalyzed reaction of Et₃Al with CHCl₃. The effects appear in the products of transformation of the diffusion radical pair of the ethyl and dichloromethyl radicals. The radical route is a side process in this reaction, and the main products, Et₂AlCl, ethane, and ethylene, are formed by a nonradical route. A general mechanism of the reactions of Et₃Al with CHCl₃ and CCl₄ including radical and ioncoordination processes was suggested. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1003–1006, May, 1999.     

Alkylaluminum activator effects on polyethylene branching using a N,N′‐nickel precatalyst appended with bulky 4,4′‐dimethoxybenzhydryl groups

Ten unsymmetrical N,N'‐bis (imino) acenaphthene‐nickel (II) halide complexes, [1‐[2,6‐{(4‐MeOC₆H₄)₂CH}₂–4‐MeC₆H₂N]‐2‐(ArN)C₂C₁₀H₆]NiX₂, each appended with one N‐2,6‐bis(4,4'‐dimethoxybenzhydryl)‐4‐methylphenyl group, have been synthesized and characterized. The molecular structures of Ni1 , Ni3 , Ni5 and Ni6 highlight the variation in steric protection afforded by the inequivalent N‐aryl groups; a distorted tetrahedral geometry is conferred about each nickel center. On activation with diethylaluminum chloride (Et₂AlCl) or methylaluminoxane (MAO), all complexes showed high activity at 30°C for the polymerization of ethylene with the least bulky bromide precatalysts ( Ni1 and Ni4 ), generally the most productive, forming polyethylenes with narrow dispersities [M_w/M_n: < 3.4 (Et₂AlCl), < 4.1 (MAO)] and various levels of branching. Significantly, this level of branching can be influenced by the type of co‐catalyst employed, with Et₂AlCl having a predilection towards polymers displaying significantly higher branching contents than with MAO [T_m: 33.0–82.5°C (Et₂AlCl) vs. 117.9–119.4°C (MAO)]. On the other hand, the molecular weights of the materials obtained with each co‐catalyst were high and, in some cases, entering the ultra‐high molecular weight range [M_w range: 6.8–12.2 × 10⁵ g mol^?1 (Et₂AlCl), 7.2–10.9 × 10⁵ g mol^?1 (MAO)]. Furthermore, good tensile strength (ε_b up to 553.5%) and elastic recovery (up to 84%) have been displayed by selected more branched polymers highlighting their elastomeric properties.     

Alternating copolymer of butadiene and propylene. IV. Studies on the catalysts for alternating copolymerization

The catalysts for alternating copolymerization of butadiene and propylene were investigated by means of ESR technique and potentiometric titration. It was found that several kinds of active species for the production of alternating copolymer, 1,2-polybutadiene, and trans-1,4-polybutadiene are formed, depending upon the catalyst composition of VO(acac)₂? Et₃Al? Et₂AlCl. ESR and potential titration studies suggest that the active species for alternating copolymerization is a divalent vanadium compound existing in an associated form.     

Polymerization of linear higher α-olefins with a modified Ziegler catalyst

The polymerization of hexene-1, octene-1 and decene-1 with a modified Ziegler catalyst based on the product of interaction of TiCl₄, Et₂AlCl, and n-Bu₂O in toluene has been studied. Et₂AlCl, i-Bu₂AlCl, and a combination of Et₂AlCl with MgBu₂ were used as cocatalysts. The addition of a small amount of MgBu₂ to Et₂AlCl resulted in a sharp increase in the catalytic system activity along with decreases in the molecular masses of the formed polymers. It has been shown that a change of [Mg]/[Al] ratio makes it possible to produce polyolefins in a wide range of molecular masses with high effectiveness. The above mentioned polymers are amorphous ultrahigh molecular materials with predominantly isotactic structure.     

The reactions of nickel(II) carboxylates with a series of ethylaluminum chlorides

The distribution of nickel in the reaction products from the reactions of nickel(II) stearate with diethylaluminum chloride (Et₂AlCl), ethylaluminum sesquichloride (Et₃Al₂Cl₃), and ethylaluminum dichloride (EtAlCl₂) in benzene was investigated as a function of the Al/Ni reaction stoichiometry. The products consist of benzene-soluble nickel complexes and a precipitate from which can be extracted NiCl₂ and metallic nickel. The percentage of each product is seen to be dependent upon the Al/Ni reaction ratio and the aluminum compound employed in the reaction. It was found that in each case six alkylaluminums are required for complete reaction with one nickel(II) stearate molecule. The compunds Et₂AlCl, Et₃Al₂Cl₃, and EtAlCl₂ were all found to have greater reducing ability than Et₃Al at room temperature. Alternative interpretations of the chloro compounds' greater reducing abilities are discussed.     

Molecular weight control of polyethylene waxes using a constrained imino‐cyclopenta[b]pyridyl‐nickel catalyst

Five examples of nickel(II) bromide complexes bearing N,N‐imino‐cyclopenta[b ]pyridines, [7‐(ArN)‐6,6‐Me₂C₈H₅N]NiBr₂ (Ar = 2,6‐Me₂C₆H₃ ( Ni1 ), 2,6‐Et₂C₆H₃ ( Ni2 ), 2,6‐i‐ Pr₂C₆H₃ ( Ni3 ), 2,4,6‐Me₃C₆H₂ ( Ni4 ), 2,6‐Et₂‐4‐MeC₆H₂ ( Ni5 )), have been prepared by the reaction of the corresponding ligand, L1 – L5 , with NiBr₂(DME) (DME = 1,2‐dimethoxyethane). On crystallization from bench dichloromethane, Ni1 underwent adventitious reaction with water to give the aqua salt, [ L1 NiBr(OH₂)₃][Br] ( Ni1' ). The molecular structures of Ni1' and Ni3 have been structurally characterized, the latter revealing a bromide‐bridged dimer. On activation with either MMAO or Et₂AlCl, Ni1 , Ni2 , Ni4, and Ni5 , all exhibited high activities for ethylene polymerization (up to 3.88 × 10⁶ g(PE) mol^?1(Ni) h^?1); the most sterically bulky Ni3 gave only low activity. Polyethylene waxes are a feature of the materials obtained which typically display low molecular weights (M _ws), narrow M _w distributions and unsaturated vinyl and vinylene functionalities. Notably, the catalyst comprising Ni1 /Et₂AlCl produced polyethylene with the lowest M _w, 0.67 kg mol^?1, which is less than any previously reported data for any class of cycloalkyl‐fused pyridine–nickel catalyst. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3494–3505     

Ethylaluminum oxide catalysts from Et2AlOLi–Et2AlCl binary system in relation to species of AlEt3–water catalyst

Equimolar reaction of Et₂AlOLi and Et₂AlCl gave Et₂AlOAlEt₂. The catalyst behavior for polymerization of acetaldehyde, propylene oxide, and epichlorohydrin was compared with that of the AlEt₃–H₂O (1:0.5) catalyst system. The thermal disproportionation product of Et₂AlOAlEt₂ derived from Et₂AlOLi–Et₂AlCl had the structure, ? (EtAlO)_n? , and it showed catalyst behavior quite similar to that of the product obtained by the same treatment of AlEt₃–H₂O (1:0.5). These ethylaluminum oxides can be regarded as species predominating in AlEt₃–H₂O (1:0.5) and AlEt₃–H₂O (1:1), respectively. Stereospecific or high molecular weight polymerizations of these species were investigated.     

Regioselective [6π+2π] cycloaddition of 1,2-dienes to 7-substituted 1,3,5-cycloheptatrienes catalyzed by Ti(acac)2Cl2—Et2AlCl

A reaction of 7-alkyl-, 7-allyl-, 7-phenyl-1,3,5-cycloheptatrienes with 1,2-dienes in the presence of the two-component catalytic system Ti(acac)₂Cl₂—Et₂AlCl, which led to the formation of practically important substituted endo-bicyclo[4.2.1]nona-2,4-dienes in up to 90% yields, was accomplished for the first time.     

Chemically induced dynamic nuclear polarization and reaction of Et3Al with CCl4 catalyzed by Ni(acac)2

The influence of Ni(acac)₂ added in catalytic amounts on the chemically induced dynamic nuclear polarization (CIDNP) effects, the mechanism of interaction, and the products of reaction between Et₃Al and CCl₄ were studied. The radical intermediates were identified and the routes for their transformations were proposed. The thermal reaction of Et₃Al with CCl₄ occurs by a radical mechanism. However, in the presence of Ni(acac)₂, the reaction proceeds mainlyvia a nonradical route and gives large amounts of ethylene and ethane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1580–1583, August, 1998.     

Achieving branched polyethylene waxes by aryliminocycloocta[b]pyridylnickel precatalysts: Synthesis,characterization, and ethylene polymerization

Cycloocta[b ]pyridin‐10‐one was prepared to form the corresponding imino derivatives, which then reacted with (DME)NiBr₂ to form 10‐aryliminocycloocta[b ]pyridylnickel bromides ( Ni1 – Ni5 ). The new compounds were characterized by means of FT‐IR spectroscopy as well as elemental analysis and the organic ligands were also analyzed by the NMR measurements. Furthermore, the molecular structure of a representative complex Ni3 was determined by the single crystal X‐ray diffraction, indicating the distorted tetrahedral geometry around the nickel atom. Upon the activation with either methylaluminoxane (MAO) or diethylaluminium chloride (Et₂AlCl), the title nickel complexes exhibited high activity in ethylene polymerization and produced polyethylene of low molecular weight (1.43–6.78 kg mol^?1) and low dispersity (1.7–2.4), which suggests a single‐site catalytic system. More importantly, the microstructure of the resultant polyethylene (especially degree of branching) and certain physical properties, such as T _m values, can easily be modulated by selecting the proper substituents within the ligands and adjusting the polymerization conditions. This finding demonstrates that it is plausible to use a single catalyst for synthesizing different types of polyethylene on demand.10‐Aryliminocycloocta[b ]pyridylnickel bromides ( Ni1–Ni5 ), upon activation with either MAO or Et₂AlCl, exhibited high activity towards ethylene polymerization and produced polyethylenes with low molecular weight (1.43–6.78 kg mol^?1) and low dispersity (1.7–2.4). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2601–2610     

Stereoregular polymerization of 1-vinylnaphthalene, 2-vinylnaphthalene,and 4-vinylbiphenyl

1-Vinylnaphthalene, 2-vinylnaphthalene, 4-vinylbiphenyl, and styrene were polymerized with Et₃Al–TiCl₄, Et₂AlCl–TiCl₃, and Et₃Al–TiCl₃ catalyst systems. The latter catalyst system gave polymers in 75–95% conversion which were at least 90% isotactic. Extraction with 2-butanone (MEK) separated the atactic from the isotactic fractions. The polymers were characterized by infrared and nuclear magnetic resonance spectroscopy.     

Synthesis and ethylene polymerization of 8‐(fluorenylarylimino)‐5,6,7‐trihydroquinolylnickel chlorides: Tailoring polyethylenes by adjusting fluorenyl position and adduct Et2Zn

A series of 8‐(arylimino)‐5,6,7‐trihydroquinolines ligand pendant fluorenyl group at N‐aryl ring, and their nickel complexes ( Ni1 ? Ni5 ) have been prepared and characterized. Once activated with Et₂AlCl, the complexes Ni1 , Ni2 , and Ni3 bearing ligands from para‐fluorenylaniline produced unimodal polyethylenes; on the contrary complexes Ni4 and Ni5 gave bimodal polyethylenes due to steric influence of ligands from ortho‐fluorenyl anilines. With a increment of Et₂Zn/ Ni4 ratio from 0 to 400, the distinct bimodel polyethylenes were obtained with molecular weights shifted from 14.3 to 57.6 kg·mol^?1; apart shiftment to higher molecular weights, the portion of low molecular weight decreased along with higher portion of high molecular weight. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1910–1919     

Carbon monoxide poisoning as a probe for the active site(s) of a nickel-based olefin oligomerization catalyst

The interaction of the olefin oligomerization catalyst system derived from [Ni(sacsac)(PBu₃)Cl] (sacsac = pentane-2,4-dithionate = dithioacetylacetonate) with carbon monoxide (CO) has been examined by a combination of ³¹P NMR and FTIR spectroscopy. The catalyst is rapidly and completely inhibited by CO; however, removal of the CO restores catalytic activity. A CO-adduct of the active catalyst has a characteristic CO stretching frequency of 2042 cm^?1, and δ³¹P 9.9 ppm. Carbon monoxide does not react with [Ni(sacsac)(PBu₃)Cl], but [Ni(sacsac)(PBu₃)(Cl)] reacts with any of Et₂AlCl, BuLi, Li[Et₃BH] or K[(s-Bu)₃BH] under an atmosphere of carbon monoxide in the presence or absence of olefin to produce [Ni(PBu₃)(CO)₃], which has been identified by FTIR and ³¹P NMR. [Ni(sacsac)(PBu₃)Cl] reacts completely with BuLi or K[(s-Bu)₃BH] to form catalytically inactive species which yield active catalysts on addition of Et₂AlCl.     

Catalytic [6<Emphasis Type="Italic">π</Emphasis> + 2<Emphasis Type="Italic">π</Emphasis>]-Cycloaddition of 1,2-Dienes to Bis(cyclohepta-1,3,5-trien-7-yl)alkanes in the Presence of Ti(acac)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>,–Et<Subscript>2</Subscript>AlCl

An efficient procedure has been developed for the synthesis of difficultly accessible 9,9′-(alkane-α,ω-diyl)bis[7-(diphenylmethylidene)bicyclo[4.2.1]nona-2,4-dienes] and 16,16′-(alkane-α,ω-diyl)bis(tricyclo-[9.4.1.0^2,10]hexa-2,12,14-trienes) in 55–84% yields by [6π + 2π]-cycloaddition of 7,7′-(alkane-α,ω-diyl)bis-(cyclohepta-1,3,5-trienes) to 1,1-diphenylpropa-1,2-diene and cyclonona-1,2-diene in the presence of the catalytic system Ti(acac)₂Cl₂–Et₂AlCl. The structure of the isolated compounds has been reliably proved by modern spectral methods.