Substituent and Solvent Effects in the Insertion and Isomerization of Olefins by Platinum(bis-phosphine) Complexes: An ab Initio Study of the Pt(PR3)2H(propene)+ Model Systems
| Autor: | B. Coussens, Steven Creve, Henk Oevering |
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| Rok vydání: | 1999 |
| Předmět: | |
| Zdroj: | Organometallics. 18:1967-1978 |
| ISSN: | 1520-6041 0276-7333 |
| DOI: | 10.1021/om9806895 |
| Popis: | Traditional ab initio (HF, MP2) and density functional theory (DFT) calculations are applied on the cationic Pt(PR3)2(H)(propene)+ complexes (R = H, F, CH3) in order to study the insertion of propene in the Pt−H bond. In general, insertion and β-elimination barriers tend to be small. Insertion barriers of about 10 kJ/mol are found for R = H and 3−9 kJ/mol for R = CH3, and an almost negligible insertion barrier appears for R = F (2−4 kJ/mol). Since propene insertion can generate both linear propyl and branched isopropyl complexes, it is possible to study the distribution between these two complexes, which is of importance for catalyst selectivity. It turns out that linear complexes are favored over branched ones, in agreement with available experimental data. The energy gap between the two forms decreases in the order R = Me > R = H > R = F. Another point of interest is the double-bond isomerization of propene which can arise from isopropyl complexes. Two pathways are identified: a direct exchange of β-hy... |
| Databáze: | OpenAIRE |
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