Nickel Catalyzed Oligomerization of Alkenes and Related Reactions

Jolly, P. W.

doi:10.1016/b978-008046518-0.00116-1

Cited by 24 publications

(2 citation statements)

References 167 publications

(64 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In previous studies, we reported the use of the aluminum-free cationic complex [Ni(η 3 -(2-methylallyl))(η 4 -(1,5-cyclooctadiene))]PF 6 , 1 , as a very active homogeneous catalyst precursor for the low molecular weight polymerization of styrene. According to the classical work of Wilke and co-workers, the addition of phosphine and phosphite ligands to allyl nickel compounds strongly influences their activity and selectivity toward C−C bond formation reactions . Particularly, in the case of 1 + PCy 3 (Cy = cyclohexyl), we reported the first case of isotactic polymerization of styrene performed in the homogeneous phase .…”

Section: Introductionmentioning

confidence: 92%

Isospecific Oligo-/Polymerization of Styrene with Soluble Cationic Nickel Complexes. The Influence of Phosphorus(III) Ligands

Ascenso¹,

Dias²,

Gomes³

et al. 1996

Macromolecules

View full text Add to dashboard Cite

The influence of several phosphorus(III) ligands upon the activity and the stereoregulation ability of the soluble organometallic complex [Ni(η3-(2-methylallyl))(η4-COD)]PF6 (COD = 1,5-cyclooctadiene), 1, is studied. There is a general increase of the catalytic activity which can be associated with the P(III) ligand's lability. A detailed analysis of the mass distribution and microstructure is carried out by GPC and 1H and 13C NMR of the solvent-fractionated polymers. In the majority of cases, regioregular low molecular weight polymers with the structure PhCHCH2[CH(Ph)CH2] n CH(Ph)CH3 are obtained. The addition of bulky phosphines, such as P(o-Tol)3 (o-Tol = o-tolyl) and PCy3 (Cy = cyclohexyl), affords highly isotactic oligomers (≈90%). For the latter, the regioselectivity of the chain growth is broken during the insertion of the last monomer, which results in the formation of a tail-to-tail end group, CH2C(C6H5)CH(C6H5)CH2−. The superimposed effects of η3-coordination of the chain end and the large stereochemical influence of these ligands seem to be the reason for the observed isospecifity.

show abstract

Section: Introductionmentioning

confidence: 92%

Isospecific Oligo-/Polymerization of Styrene with Soluble Cationic Nickel Complexes. The Influence of Phosphorus(III) Ligands

Ascenso¹,

Dias²,

Gomes³

et al. 1996

Macromolecules

View full text Add to dashboard Cite

show abstract

“…Does the electronic effect of ligands, as expected, substantially change the polarity of metal-carbon bonds, and thereby influence isomerization equilibria'O) of alkyl transition metal complexes? This could lead to the design of more selective catalysts for processes such as hydroformylation, or the hydrocyanation of butadiene to adiponitrile [76]. 28).…”

Section: Transition Metal Alkyl Complexesmentioning

confidence: 99%

Electronegativity Effects in Organic Synthesis: Differences in stability of isomeric substituted alkanes

Harvey

Viehe

1995

J. Prakt. Chem.

View full text Add to dashboard Cite

Selectivity is such an intellectually, economically, and ecologically important matter in organic synthesis that it is highly desirable to know all the factors, both kinetic and thermodynamic, which influence it. We were surprised by the high selectivity obtained in an equilibration of isomeric β‐thioalkyl trifluoroacetates, because the thermodynamic difference implied by this and other, similar, rearrangements did not appear to have been explained. It now appears that this difference is due to the thermochemical effect whereby polar substituents bind more strongly to alkyl groups of complementary polarity; in other words electronegative atoms prefer more „procationic”︁ tertiary and secondary alkyl groups, electropositive ones prefer the more „proanionic”︁ primary alkyl and methyl groups. This small but significant (1 to 7 kcal·mol−1) effect is well documented by thermochemical data, and has been described several times; it can be predicted qualitatively by Pauling's formula relating bond energy, bond polarisation, and electronegativity. We first describe how the electronegativity effect explains our observations: they are due to the higher electronegativity of oxygen and chlorine relative to that of sulfur. We then go on to show that it is useful for the interpretation of many other literature reports, ranging from the acid‐catalysed isomerization of alkyl halides, to the carbocyclization of organozinc reagents, and the isomerization of alkyltransition metal complexes (a key step for the selectivity of important industrial processes such as alkene hydroformylation).

show abstract