Highly regioselective osmium-catalyzed hydroformylation

2015 ◽  
Vol 51 (15) ◽  
pp. 3080-3082 ◽  
Author(s):  
Lipeng Wu ◽  
Qiang Liu ◽  
Anke Spannenberg ◽  
Ralf Jackstell ◽  
Matthias Beller
Keyword(s):  
Active Species ◽  
Phosphine Ligands ◽  
Catalyst Structure ◽  
Osmium Carbonyl

Osmium carbonyl combined with 2-imidazoyl-substituted phosphine ligands forms active species for the highly regioselective and general hydroformylation of alkenes to produce aldehydes in good yields and excellent regioselectivities. An unusual phosphido bridged trinuclear osmium catalyst structure was obtained.

scholarly journals Late 3d Metal-Catalyzed (Cross-) Dimerization of Terminal and Internal Alkynes

2021 ◽  
Vol 9 ◽  
Author(s):  
Sebastian M. Weber ◽  
Gerhard Hilt
Keyword(s):  
Nickel Catalysts ◽  
Active Species ◽  
Phosphine Ligands ◽  
Cobalt Catalysts ◽  
Crucial Effect ◽  
Internal Alkynes ◽  
Bidentate Phosphine ◽  
Dimerization Product ◽  
Metal Catalyzed ◽  
Cobalt And Nickel

This review will outline the recent advances in chemo-, regio-, and stereoselective (cross-) dimerization of terminal alkynes to generate 1,3-enynes using different types of iron and cobalt catalysts with altering oxidation states of the active species. In general, the used ligands have a crucial effect on the stereoselectivity of the reaction; e.g., bidentate phosphine ligands in cobalt catalysts can generate the E-configured head-to-head dimerization product, while tridentate phosphine ligands can generate either the Z-configured head-to-head dimerization product or the branched head-to-tail isomer. Furthermore, the hydroalkynylation of silyl-substituted acetylenes as donors to internal alkynes as acceptors will be discussed using cobalt and nickel catalysts.

scholarly journals Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)

2020 ◽  
Author(s):  
Megan Greaves ◽  
Thomas O. Ronson ◽  
Guy Lloyd-Jones ◽  
Feliu Maseras ◽  
Stephen Sproules ◽  
...  
Keyword(s):  
Alkyl Radical ◽  
Nickel Complex ◽  
Cross Coupling ◽  
Active Species ◽  
Alkyl Halides ◽  
Phosphine Ligands ◽  
Coupling Reactions ◽  
Alternative Pathways ◽  
Cross Coupling Reactions ◽  
Abstraction Reaction

The mechanism of the reactions between dppf-Ni0 complexes and alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(dppf)2], which undergoes a halide abstraction reaction with alkyl halides and rapidly captures the alkyl radical that is formed. The yields in prototypical nickel-catalysed Kumada cross-coupling reactions are shown to be improved by the addition of free phosphine ligands<br>

scholarly journals Real-time analysis of Pd2(dba)3 activation by phosphine ligands

2017 ◽  
Vol 53 (5) ◽  
pp. 854-856 ◽  
Author(s):  
Eric Janusson ◽  
Harmen S. Zijlstra ◽  
Peter P. T. Nguyen ◽  
Landon MacGillivray ◽  
Julio Martelino ◽  
...  
Keyword(s):  
Real Time ◽  
Active Species ◽  
Phosphine Ligands ◽  
Time Analysis ◽  
Esi Ms ◽  
Real Time Analysis ◽  
Insight Into

Real-time UV-Vis/ESI-MS monitoring of Pd2(dba)3 activation provides insight into active species and the effect of activation protocol on their formation.

scholarly journals Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Oligoethylenes and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

2021 ◽  
Author(s):  
Ilaria D'Auria ◽  
Zeinab Saki ◽  
Claudio Pellecchia
Keyword(s):  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Variable Content ◽  
Peculiar Behavior ◽  
Number Of Branches

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart's &alpha;-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e. the number of branches of the produced polyethylenes increases while ethylene pressure increases.

scholarly journals In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition under acidic conditions

2021 ◽  
Author(s):  
Chaoren Shen ◽  
Kaiwu Dong ◽  
Zhihong Wei ◽  
Xinxin Tian
Keyword(s):  
Formic Acid ◽  
In Silico ◽  
Active Species ◽  
Phosphine Ligands ◽  
Tertiary Phosphine ◽  
Promoting Effect ◽  
Pyridyl Group ◽  
Acidic Conditions ◽  
Releasing Process ◽  
Previous Experimental Study

In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition to carbon monoxide under acidic conditions was conducted. Two types of bidentate tertiary phosphine ligands were selected on the basis of previous experimental study. And the promoting effect of para-toluenesulfonic acid (PTSA) was specifically investigated. The pyridyl group implanted in pytbpx ligand is found to mainly contribute on enhancing the activity of palladium catalyst. The PTSA promoter displays specific role for regenerating active species and supressing dehydrogenation during Pd-pytbpx/Pd-dtbpx catalysed dehydration process. CO releasing process catalysed by Pd-dtbpx also facilitated by adding PTSA. According to the mechanism hereby supposed, introducing electron-withdrawing substitution at para-position of pyridyl rings may further improve the dehydrative decomposition activity of Pd-pytbpx.

scholarly journals Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)

2020 ◽  
Author(s):  
Megan Greaves ◽  
Thomas O. Ronson ◽  
Guy Lloyd-Jones ◽  
Feliu Maseras ◽  
Stephen Sproules ◽  
...  
Keyword(s):  
Alkyl Radical ◽  
Nickel Complex ◽  
Cross Coupling ◽  
Active Species ◽  
Alkyl Halides ◽  
Phosphine Ligands ◽  
Coupling Reactions ◽  
Alternative Pathways ◽  
Cross Coupling Reactions ◽  
Abstraction Reaction

The mechanism of the reactions between dppf-Ni0 complexes and alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(dppf)2], which undergoes a halide abstraction reaction with alkyl halides and rapidly captures the alkyl radical that is formed. The yields in prototypical nickel-catalysed Kumada cross-coupling reactions are shown to be improved by the addition of free phosphine ligands<br>

scholarly journals Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Ethylene Oligomers and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

Macromol ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 121-129
Author(s):  
Ilaria D’Auria ◽  
Zeinab Saki ◽  
Claudio Pellecchia
Keyword(s):  
Active Species ◽  
Polymerization Catalysts ◽  
Reaction Conditions ◽  
Catalyst Structure ◽  
Variable Content ◽  
Peculiar Behavior ◽  
Number Of Branches ◽  
Ethylene Oligomers

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both, depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e., the number of branches of the produced polyethylenes increases while ethylene pressure increases.

Invasive species in the flora of Ukraine. I. The group of highly active species

Geo&Bio ◽  
2019 ◽  
Vol 2019 (17) ◽  
pp. 116-135 ◽  
Author(s):  
Vira V. Protopopova ◽  
◽  
Myroslav Shevera
Keyword(s):  
Invasive Species ◽  
Active Species ◽  
Highly Active
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