| Autor: |
Wen Zhou, Bruce M. Foxman, Jeremy P. Krogman, Christine M. Thomas, Noam I. Saper |
| Rok vydání: |
2013 |
| Předmět: |
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| Zdroj: |
Dalton transactions (Cambridge, England : 2003). 43(5) |
| ISSN: |
1477-9234 |
| Popis: |
The effect of modifying the N-aryl substituent (aryl = mesityl vs. m-xylyl) of the phosphinoamide ligands linking Zr and Co in tris(phosphinoamide)-linked heterobimetallic complexes has been investigated. Treatment of the metalloligand ((i)Pr2PNXyl)3ZrCl (2) (Xyl = m-xylyl) with CoI2 affords the iodide-bridged product ICo((i)Pr2PNXyl)2(μ-I)Zr(η(2-i)Pr2PNXyl) (3) rather than the C3-symmetric isomer observed using the N-mesityl derivative, ICo((i)Pr2PNMes)3ZrCl. Upon two-electron reduction of complex 3, ligand rearrangement occurs to generate the three-fold symmetric reduced complex N2Co((i)Pr2PNXyl)3Zr(THF) (4). Comparison of 4 with the previously reported mesityl-substituted complex N2Co((i)Pr2PNMes)3Zr(THF) (1) reveals similar structural features but with a less sterically hindered Zr apical site in complex 4. An obvious electronic difference between these two complexes is also present based on the drastically different infrared N2 stretching frequencies of 1 and 4. These notable differences lend themselves to different reactivity in both stoichiometric and catalytic reactions. Alkyl halide addition to complex 4 results in homo-coupling products resulting from alkyl radicals rather than the alkyl-bridged or intramolecular C-H activation products formed upon addition of RX to 1. This difference in reactivity with alkyl halides renders complex 3 a less effective catalyst for the Kumada cross-coupling of alkyl halides with n-octylMgBr than ICo((i)Pr2PNMes)3ZrCl, as a greater proportion of homocoupling products are formed under catalytic conditions. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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