Potential Hemilabile (Imino)pyridine Palladium(II) Complexes as Selective Ethylene Dimerization Catalysts: An Experimental and Theoretical Approach

Nyamato, George S.; Ojwach, Stephen O.; Akerman, Matthew P.

doi:10.1021/acs.organomet.5b00860

Cited by 24 publications

(10 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The data in Table clearly illustrate the approximately square planar coordination geometry of the metal ion with only small deviations from ideality imposed by the ligand geometry in some cases. The bond lengths and angles are in good agreement with those previously reported for comparable asymmetric palladium (II) complexes . The most significant deviation from the ideal bond angle of 90° is the N–Pd–N bond angle which averages 86.65(12)°.…”

Section: Resultssupporting

confidence: 89%

Structural and theoretical studies of the methoxycarbonylation of higher olefins catalysed by (Pyrazolyl‐ethyl)pyridine palladium (II) complexes

Zulu

Alam

Ojwach

et al. 2019

Applied Organom Chemis

Self Cite

View full text Add to dashboard Cite

Reactions of 2-[1-(3,5-dimethylpyrazol-1-yl)ethyl]pyridine (L1) and 2-[1-(3,5diphenylpyrazol-1-yl)ethyl]pyridine (L2) with the [Pd (COD)Cl 2 ] or [Pd (COD)MeCl] produced palladium (II) complexes [Pd(L1)ClMe] (1), [Pd(L1) Cl 2 ] (C2), [Pd(L2)ClMe] (3), and [Pd(L2)Cl 2 ] (4) in quantitative yields. Solid state structures of complexes 1, 3 and 4 established the formation of mononuclear compounds, containing one bidentate ligand unit per metal atom, to give square planar complexes. All the other spectroscopic characterization data and elemental analyses were consistent with the observed structures. All the palladium (II) complexes 1-4 gave active catalysts in the methoxycarbonylation of 1-octenes. The catalysts demonstrated 100% chemoselectivities towards esters and favored the formation of linear isomers. Reaction conditions such as the type of phosphine derivative, acid promoter, solvent system, time, pressure and temperature have been investigated and shown to affect both the catalytic activity and regio-selectivity of the catalysts. Solid-angle modelling established the comparable steric contributions from the ligands, consistent with the similar regioselectivities of the resultant catalysts.

show abstract

Section: Resultssupporting

confidence: 89%

Structural and theoretical studies of the methoxycarbonylation of higher olefins catalysed by (Pyrazolyl‐ethyl)pyridine palladium (II) complexes

Zulu

Alam

Ojwach

et al. 2019

Applied Organom Chemis

Self Cite

View full text Add to dashboard Cite

show abstract

“…Very recently, for related Pd(Me)Cl complexes with the unsymmetrical N^N′ ligand 3-methoxy-N-1-(pyridin-2-yl)ethylidenepropan-1-amine and related ligands in solution, also cis and trans mixtures were observed by NMR. 70 DFT calculations revealed a very small energy difference of 0.731 kJ mol −1 in favor of the isomer with 71,72 From the four complexes showing a mixture of cis and trans isomers in solution as inferred from NMR spectroscopy (vide supra), three crystallized in the trans form. A further five complexes crystallized in the cis form, although for one of them, cis-[(PyMA)Ni(Mes)Cl], both isomers were observed in solution.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

“…From electronic considerations, one might expect a superior match of the strongly σ-donating Me coligand trans to the presumably better π-acceptor, the N -arylmethanimine group over the other isomer; however, these examples show that even with small coligands the steric bulk on the N -aryl and pyridine groups drive the formation of stereoisomers rather than the electronic trans influence, in line with our observations. Very recently, for related Pd(Me)Cl complexes with the unsymmetrical N^N′ ligand 3-methoxy- N -1-(pyridin-2-yl)ethylidenepropan-1-amine and related ligands in solution, also cis and trans mixtures were observed by NMR . DFT calculations revealed a very small energy difference of 0.731 kJ mol –1 in favor of the isomer with the Me coligand trans to the pyridine unit, in line with the molecular structure in the solid state.…”

Section: Resultsmentioning

confidence: 99%

Unsymmetrical N-Aryl-1-(pyridin-2-yl)methanimine Ligands in Organonickel(II) Complexes: More Than a Blend of 2,2′-Bipyridine and N,N-Diaryl-α-diimines?

et al. 2016

View full text Add to dashboard Cite

The new organonickel complexes [(R-PyMA)Ni(Mes)X] [R-PyMA = N-aryl-1-(pyridin-2-yl)methanimine; aryl = phenyl, 2,6-Me-, 3,5-Me-, 2,4,6-Me-, 2,6-Pr-, 3,5-(OMe)-, 2-NO-4-Me-, 4-NO-, 2-CF-, and 2-CF-6-F-phenyl; Mes = 2,4,6-trimethylphenyl; X = F, Cl, Br, or I] were obtained as approximate 1/1 cis and trans isomeric mixtures or pure cis isomers depending on the PyMA ligand and X. The [(R-PyMA)Ni(Mes)X] complexes with X = Br or Cl were directly synthesized from the precursors trans-[(PPh)Ni(Mes)X], while [(PyMA)Ni(Mes)X] derivatives with X = F or I were obtained from [(PyMA)Ni(Mes)Br] through X exchange reactions. Although density functional theory (DFT) calculations show a preference for the sterically favored cis isomers, both isomers could be observed in many cases; in three cases, even single crystals for X-ray diffraction could be obtained for the trans isomers. Possible intermediates for the isomerization were investigated by DFT calculations. All complexes were studied by multiple spectroscopic means, electrochemistry, and spectroelectrochemistry (for the reduction processes). The long-wavelength metal-to-ligand charge-transfer (MLCT) absorptions vary markedly with the R substituent of the ligand and the cathodic electrochemical potentials to a far smaller degree. Both are almost invariable upon variation of X. All of this is in line with Ni-based and π*-based lowest unoccupied molecular orbitals (LUMOs). In line with the unsymmetric character of the N^N ligand, electrochemistry and MLCT transitions seem to not correspond to the same type of π* LUMO, making these PyMA ligands more interesting than the symmetric heteroaromatic polypyridine ligands such as 2,2'-bipyridine (bpy; N^N) and N,N-diaryl-substituted aliphatic α-diimines (N^N) such as the diaza-1,3-butadienes (DAB). First attempts to use these complexes in Negishi-type cross-coupling reactions were successful.

show abstract

“…[16][17][18] In this study, we report the use of (imino)pyridine ligands to make nickel(II) complexes as potential catalysts in olefin oligomerization reactions. Attempts to use the imine ligands (L1-L4) we previously used to prepare palladium complexes 19 to synthesize nickel(II) complexes did not materialize. This could have been largely due to hydrolysis of the imine group in the ligands as reported in literature.…”

Section: Introductionmentioning

confidence: 99%

Ethylene oligomerization studies by nickel(ii) complexes chelated by (amino)pyridine ligands: experimental and density functional theory studies

2016

Self Cite

View full text Add to dashboard Cite

Reductions of imine compounds 2-methoxy-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L1), 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L2), N,N-diethyl-N-((pyridin-2-yl)methylene)ethane-1,2-diamine (L3) and 2-((pyridin-2-yl)methyleneamino)ethanol (L4) using NABH4 produced their corresponding amine analogues N-(2-methoxyethyl)-1-(pyridin-2-yl)ethanamine (L1a), 2-methoxy-N-((pyridin-2-yl)methyl)-ethanamine (L2a), N,N-diethyl-N-((pyridin-2-yl)methyl)ethane-1,2-diamine (L3a) and 2-((pyridin-2-yl)methylamino)ethanol (L4a) in good yields. Reactions of the (amino)pyridine ligands L1a–L4a with [NiBr2(DME)] afforded nickel(II) complexes, [NiBr2(L1a)2] (1), [NiBr2(L2a)2] (2), [NiBr2(L3a)2] (3) and [NiBr2(L4a)2] (4), respectively in quantitative yields. Molecular structures of complexes 2 and 4 confirmed the formation of the bis(chelated)nickel(II) complexes. Activation of complexes 1–4 with either EtAlCl2 or methylaluminoxane (MAO), produced active ethylene oligomerization catalysts to afford mostly ethylene dimers (C4), in addition to trimmers (C6) and tetramers (C8). Density functional theory studies provided valuable insight into the reactivity trends and influence of complex structure on the ethylene oligomerization reactions.

show abstract

Potential Hemilabile (Imino)pyridine Palladium(II) Complexes as Selective Ethylene Dimerization Catalysts: An Experimental and Theoretical Approach

Cited by 24 publications

References 46 publications

Structural and theoretical studies of the methoxycarbonylation of higher olefins catalysed by (Pyrazolyl‐ethyl)pyridine palladium (II) complexes

Structural and theoretical studies of the methoxycarbonylation of higher olefins catalysed by (Pyrazolyl‐ethyl)pyridine palladium (II) complexes

Unsymmetrical N-Aryl-1-(pyridin-2-yl)methanimine Ligands in Organonickel(II) Complexes: More Than a Blend of 2,2′-Bipyridine and N,N-Diaryl-α-diimines?

Ethylene oligomerization studies by nickel(ii) complexes chelated by (amino)pyridine ligands: experimental and density functional theory studies

Contact Info

Product

Resources

About