Complex isopropyl nickel

An important contribution to an understanding of the mechanism of propene dimerization has been obtained by studying the reaction of nickel-hydride model complexes (55). The formation of the propyl- and isopropyl-nickel complexes 48 and 49 has been observed in the reactions of HNi(PR3)Cl complexes (50) with propene at -78°C [Eq. (15)] ... 

Formation of n-alkylnickels by addiction of Ni hydride to an alkene is important in many nickel-catalyzed reactions such as alkene dimerization and isomerization. However, stoichiometric formation of alkylnickels from alkenes and Ni hydrides is not synthetically useful because of the reactivity of alkylnickels. The regiochemistry of the addition of HNiX(PR3)2 to propene is affected by the nature of the trialkylphosphine group used in the Ni hydride complex. The observed ratios of n-propyl- to isopropyl-nickel found after the insertion step vary from 82 18 to 82 20 to 19 81 as the phosphine is changed from P(OC6Hs)3 to P(c-C6Hu) to P(t-C4H9)2(i-C3H7). ... 

A square-planar nickel hydride complex is suggested as the catalytic species [589]. In the first step, the nickel hydride catalyst adds across the double bond of propylene to give two intermediates, namely, a propyl nickel and isopropyl nickel complex. Both of these intermediates can react further with propylene by insertion of the double bond into the nickel-carbon bond, resulting in formation of four more intermediates. ( -Elimination of nickel hydride from these intermediates produces the possible products of propylene dimerization, namely, 4-methyl-1-pen-tene, cis- and trans-4-methyl-2-pentene, 2,3-dimethyl-l-butene, n-hexene, 2-hexene, and 2-methyl-l-pentene. Terminal unbranched olefins are rapidly isomerized under the influence of catalyst by a process of repeated nickel hydride addition and elimination to the internal olefins. Therefore, under ordinary reaction conditions the yield of 4-methyl-l-pentene is low. 

The influence of phosphines on the direction of addition of nickel hydride or nickel alkyl to propylene is debatable. If it is assumed that the isopropyl nickel complex and the propyl nickel complex have the same reactivity toward propylene. 

The reaction scheme is rather complex also in the case of the oxidation of o-xylene (41a, 87a), of the oxidative dehydrogenation of n-butenes over bismuth-molybdenum catalyst (87b), or of ethylbenzene on aluminum oxide catalysts (87c), in the hydrogenolysis of glucose (87d) over Ni-kieselguhr or of n-butane on a nickel on silica catalyst (87e), and in the hydrogenation of succinimide in isopropyl alcohol on Ni-Al2Oa catalyst (87f) or of acetophenone on Rh-Al203 catalyst (87g). Decomposition of n-and sec-butyl acetates on synthetic zeolites accompanied by the isomerization of the formed butenes has also been the subject of a kinetic study (87h). 

Although the actual reaction mechanism of hydrosilation is not very clear, it is very well established that the important variables include the catalyst type and concentration, structure of the olefinic compound, reaction temperature and the solvent. used 1,4, J). Chloroplatinic acid (H2PtCl6 6 H20) is the most frequently used catalyst, usually in the form of a solution in isopropyl alcohol mixed with a polar solvent, such as diglyme or tetrahydrofuran S2). Other catalysts include rhodium, palladium, ruthenium, nickel and cobalt complexes as well as various organic peroxides, UV and y radiation. The efficiency of the catalyst used usually depends on many factors, including ligands on the platinum, the type and nature of the silane (or siloxane) and the olefinic compound used. For example in the chloroplatinic acid catalyzed hydrosilation of olefinic compounds, the reactivity is often observed to be proportional to the electron density on the alkene. Steric hindrance usually decreases the rate of... 

The cyclic voltammogram of complex 3 B"-Ni shows two quasi-reversible Ni(0)/(I) and Ni(I)/(II) redox waves at —2.5 V and —I.IV vs. Fc/Fc, respectively. Neither of the two oxidized complexes was isolable, most likely due to the masking of the low-valent nickel(O) center by the three ter -butyl substituents on the carbene ligand. The search for alternative routes to these complexes using less sterically bulky NHC ligands, such as the TIMEN isopropyl derivative, is under investigation. 

As indicated in Scheme 27, indoles may be alkylated by their acid-catalyzed reaction with alcohols. Similarly, r-butylation of pyrroles has been effected by the acid-catalyzed reaction with t- butyl acetate (B-77MI30502), and the diarylmethylation of 1-methylpyrrole from the acid-catalyzed reaction with the chromium trichloride complex of the diarylcarbinol has been described (78JA4124). The alkylation of indoles by alcohols in the presence of the aluminum alkoxide and Raney nickel appears to be efficient for the synthesis of 3-substituted indoles, but is less successful in the alkylation of 2-methylindole (79JHC501). The corresponding isopropylation of pyrrole produces 2,5-diisopropylpyrrole and 1-isopropylpyrrolidine, as the major products (79JHC501). 

The thermally stable nickel and palladium hydride complexes, trans-[MHX(PR3)2], where M = Ni or Pd, R = cyclohexyl or isopropyl, and X = halogen, have been prepared by various methods.1-5 Hydrido[tetra-hydroborato( 1 - )] complexes can be prepared from them by metathet-ical reactions.3 The hydrido[tetrahydroborato( 1 — )]bis(tricyclohexylphos-... 

One of the more extraordinary recent developments in nickel and palladium polyalkene catalysis has been the development of a-diimines with bulky substituents as ligands in nickel and palladium complexes. When bulky aryl groups are used (R = isopropyl), these catalysts polymerize ethylene with high activities to high molecular weight highly branched... 

Other rate processes studied include isopropyl group rotation, (529) restricted rotations in phosphine derivatives of cyclopentadienyl complexes of iron and nickel, (530) and ring and nitrogen inversion in (en) complexes of praseodymium. (531) Molecular geometries of molecules in solution can be accurately determined from NMR spectra of the molecules oriented in a nematic phase of a liquid crystalline solvent. The effect of Eu(dpm), on the nematic phase spectrum of pyridine has been examined. The pyridine geometry is unaffected by the LSR. The observed LIS values can be separated into isotropic and anisotropic components. (532)... 

The general catalytic performance of these metal complexes in polymerization of olefins was screened by the following standard procedure The complexes (50 or 100 pmol) were activated with 100 mole equivalents of methylalumoxane (MAO) in toluene solution. The polymerization reaction was carried out at a temperature of 30°C, during which ethene was added with a flow of 40 L h"t After 4.5 h, the mixture was quenched with methanol, the solid polymer isolated, washed and dried. For benchmarking a nickel diimine complex [12a] with 2,6-(di-isopropyl) phenyl substituents at the imine nitrogen atoms (133) was also included. Tab. 3.2 shows the activity and polymer data. 

HCN also adds to alkenes in the presence of an appropriate catalyst (Arthur et al., 1954 Jackson and Level, 1982). Thus, cobalt carbonyl leads to Markownikov addition, for example, 1-propene yields isopropyl cyanide in approximately 75% yield. HCN adds to alkynes in the presence of metal complexes, and the use of a nickel complex may lead to syn addition (Jackson and Level, 1983 Jackson et al., 1988). Hydrogen cyanide reacts with conjugated dienes, the mechanism involving a TT-allyl intermediate. The course of addition is complex and may lead to more than one product (Keim et al., 1982). 

C9H14O, 2-Cyclopentene-l-one, 2,3,4,5-tetramethyl-, 29 195 C,H,j02, 4W-pyran-4-one, 2,3,5,6-tetra-hydrido-2,3,5,6-tetramethyl-, 29 193 QHjiOjP, Isopropyl phosphite, nickel complex, 28 101... 

NdC4jHj9, Neodymium, tris(2,6-dwert-butyl-4-methylphenoxo)-, 27 167 O3PC3H, Trimethyl phosphite, cobalt and rhodium complexes, 28 283,284 iron complexes, 28 171, 29 158 nickel complex, 28 101 O3PCJH15, Triethyl phosphite, iron complexes, 28 171, 29 159 nickel complex, 28 101 nickel, palladium, and platinum complexes, 28 104-106 03PC,H2i, Isopropyl phosphite, nickel complex, 28 101... 

Chiral 3-acetyl-4,5-dihydro-l,2,4-triazinones (R = methyl, isopropyl, benzyl) were reacted, utilizing the template effect, with 1,3-diaminopropane in the presence of nickel acetate to give chiral tetraaza-type nickel complexes 203 (Figure 12) <2002MI31>. 

Peracylated 1,2-thio-orthoesters derived from a-n-glucopyranose [e.g. (121)], methyl o-glucopyranuronate, and a-lactose gave the l,2-(ethyl or isopropyl orthoester) derivatives when treated with Raney nickel in ethanol or propan-2-ol, respectively, although complex alcohols e.g. t-butanol) failed to yield ortho-... 

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