Barriers for Arene C−H Bond Activation in Platinum(II) η2-Arene Intermediates
| Autor: | Cynthia M. Norris, Stefan Reinartz, Joseph L. Templeton, Peter S. White |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Organometallics. 21:5649-5656 |
| ISSN: | 1520-6041 0276-7333 |
| DOI: | 10.1021/om020526n |
| Popis: | Protonation of platinum(IV) complexes of the type Tp‘Pt(Ar)(H)(R) [Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate; Ar = aryl; R = H, C6H5] with [H(OEt2)2][BAr‘4] [BAr‘4 = tetrakis(3,5-trifluoromethylphenyl)borate] results in the formation of cationic platinum(II) η2-arene complexes [κ2-(HTp‘)Pt(η2-HAr)(R)][BAr‘4] [Ar = C6H5, R = H (2); Ar = MeC6H4, R = H (4); Ar = 3,6-Me2C6H3, R = H (6); Ar = R = C6H5 (8)]. A barrier of 9.4 kcal/mol for platinum migration around the η2-p-xylene ring was calculated for complex 6 at 183 K following variable-temperature NMR measurements. Eyring analysis of hydrogen exchange between the bound benzene and the hydride ligand for cationic benzene complex 2 indicates ΔH⧧ = 11.7 ± 0.5 kcal mol-1 and ΔS⧧ = −3.8 ± 2 cal mol-1 K-1. This process is assumed to proceed via arene C−H oxidative addition to give the five-coordinate platinum(IV) phenyl dihydride intermediate 2a. Isolation of ground state η2-arene adducts with adjacent hydride ligands has allowed the barrier to oxidative add... |
| Databáze: | OpenAIRE |
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