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Published July 24, 2013 | Supplemental Material
Journal Article Open

Formation of Trivalent Zirconocene Complexes from ansa-Zirconocene-Based Olefin-Polymerization Precatalysts: An EPR- and NMR-Spectroscopic Study


Reduction of Zr(IV) metallocenium cations with sodium amalgam (NaHg) produces EPR signals assignable to Zr(III) metallocene complexes. The chloro-bridged heterodinuclear ansa-zirconocenium cation [(SBI)Zr(μ-Cl)_2AlMe_2]^+ (SBI = rac-dimethylsilylbis(1-indenyl)), present in toluene solution as its B(C_6F_5)_4^– salt, thus gives rise to an EPR signal assignable to the complex (SBI)Zr^(III)(μ-Cl)_2AlMe_2, while (SBI)ZrIII-Me and (SBI)Zr^(III)(μ-H)_2Al^(i)Bu_2 are formed by reduction of [(SBI)Zr(μ-Me)_2AlMe_2]^+ B(C_6F_5)_4– and [(SBI)Zr(μ-H)_3(AliBu_2)_2]^+ B(C_6F_5)_4^–, respectively. These products can also be accessed, along with (SBI)ZrIII-iBu and [(SBI)ZrIII]^+ AlR_4^–, when (SBI)ZrMe_2 is allowed to react with HAl^(i)Bu_2, eliminating isobutane en route to the Zr(III) complex. Further studies concern interconversion reactions between these and other (SBI)Zr(III) complexes and reaction mechanisms involved in their formation.

Additional Information

© 2013 American Chemical Society. Received: March 29, 2013; Published: June 10, 2013. This research was supported by Deutsche Forschhungsgemeinschaft (Grant Me1388/9-1), by the Russian Foundation of Basic Research (Grant 10-03-91330) and by US DOE, Office of Basic Energy Sciences (Grant DE-FG03-85ER13431). We thank Prof. Jay A. Labinger (California Institute of Technology), Dr. Konstantin P. Bryliakov (Boreskov Institute of Catalysis,) and Prof. Heiko Möller (University of Konstanz) for helpful discussions; Anke Friemel, Evelyn Wuttke, Martin Spitzbarth (University of Konstanz), David VanderVelde, and Angelo DiBilio (California Institute of Technology) for help with the acquisition and analysis of NMR and EPR spectra; and Lawrence M. Henling and Thomas S. Teets for assistance with mounting crystals and solving cyrstal structures. The Bruker KAPPA APEXII X-ray diffractometer was purchased via an NSF CRIF:MU award to the California Institute of Technology (CHE-0639094).

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Supplemental Material - ja403170u_si_001.pdf

Supplemental Material - ja403170u_si_002.cif


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