Dataset Information

Highly Efficient Ethylene Tetramerization Using Cr Catalysts Constructed with Trifluoromethyl-Substituted N-Aryl PNP Ligands.

ABSTRACT: Tetramerization of ethylene by chromium catalysts stabilized with functionalized N-aryl phosphineamine ligands C₆H₄(m-CF₃)N(PPh₂)₂ (1), C₆H₄(p-CF₃)N(PPh₂)₂ (2), C₆H₄(o-CF₃)N=PPh₂-PPh₂ (3), and C₆H₃(3,5-bis(CF₃))N(PPh₂)₂ (4) was evaluated. The parameter optimization includes temperature, co-catalyst, and solvent. Upon activation with MMAO-3A, the new catalyst system especially with m-functional PNP ligand (1) exhibited high 1-octene selectivity and productivity while giving minimum undesirable polyethylene and C₁₀ ⁺ olefin by-products. Using PhCl as a solvent at 75 °C led to a remarkable α-olefin (1-C₆ + 1-C₈) selectivity (>90 wt %) at a reaction rate of 2000 kg·g_Cr ^-1·h^-1. Under identical conditions, analogous PNP ligands bearing -CH₃, -Et, and -Cl functional moieties at the meta position of the N-phenyl ring displayed significantly lower reactivity. The catalyst with p-functional ligand (2) exhibited lower activity and comparable selectivities, while the Cr/PPN (with ligand 3) system gave no noticeable reactivity. The molecular structure of the precatalyst (1-Cr), exhibiting a monomeric structural feature, was elucidated with the aid of single-crystal X-ray diffraction study.

SUBMITTER: Jaseer EA

PROVIDER: S-EPMC9118391 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Highly Efficient Ethylene Tetramerization Using Cr Catalysts Constructed with Trifluoromethyl-Substituted N-Aryl PNP Ligands.

Jaseer E A EA Garcia Nestor N Barman Samir S Khawaji Motaz M Xu Wei W Alasiri Hassan H Peedikakkal Abdul Malik P AMP Akhtar Muhammad Naseem MN Theravalappil Rajesh R

ACS omega 20220503 19

Tetramerization of ethylene by chromium catalysts stabilized with functionalized N-aryl phosphineamine ligands C6H4(m-CF3)N(PPh2)2 (1), C6H4(p-CF3)N(PPh2)2 (2), C6H4(o-CF3)N=PPh2-PPh2 (3), and C6H3(3,5-bis(CF3))N(PPh2)2 (4) ...[more]

PMID: 35601288

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Project description:A series of tetrathiafulvalenes functionalized with one or two trifluoromethyl electron-withdrawing groups (EWG) is obtained by phosphite coupling involving CF3-substituted 1,3-dithiole-2-one derivatives. The relative effects of the EWG such as CF3, CO2Me and CN on the TTF core were investigated from a combination of structural, electrochemical, spectrochemical and theoretical investigations. Electrochemical data confirm the good correlations between the first oxidation potential of the TTF derivatives and the σmeta Hammet parameter, thus in the order CO2Me < CF3 < CN, indicating that, in any case, the mesomeric effect of the substituents is limited. Besides, crystal structure determinations show that the deformation of the unsymmetrically substituted dithiole rings, when bearing one, or two different EWG, and attributed to the mesomeric effect of ester or nitrile groups, is not notably modified or counter-balanced by the introduction of a neighboring trifluoromethyl group. DFT calculations confirm these observations and also show that the low energy HOMO-LUMO absorption band found in nitrile or ester-substituted TTFs is not found in TTF-CF3, where, as in TTF itself, the low energy absorption band is essentially attributable to a HOMO→LUMO + 1 transition. Despite relatively high oxidation potentials, these donor molecules with CF3 EWG can be involved in charge transfer complexes or cation radical salts, as reported here for the CF3-subsituted EDT-TTF donor molecule. A neutral charge transfer complex with TCNQ, (EDT-TTF-CF3)2(TCNQ) was isolated and characterized through alternated stacks of EDT-TTF-CF3 dimers and TCNQ in the solid state. A radical cation salt of EDT-TTF-CF3 is also obtained upon electrocrystallisation in the presence of the FeCl4 (-) anion. In this salt, formulated as (EDT-TTF-CF3)(FeCl4), the (EDT-TTF-CF3)(+•) radical cations are associated two-by-two into centrosymmetric dyads with a strong pairing of the radical species in a singlet state.

Dataset Information

Highly Efficient Ethylene Tetramerization Using Cr Catalysts Constructed with Trifluoromethyl-Substituted N-Aryl PNP Ligands.

Publications

Highly Efficient Ethylene Tetramerization Using Cr Catalysts Constructed with Trifluoromethyl-Substituted <i>N</i>-Aryl PNP Ligands.

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