Addition of methyl triflate to a hafnocene dinitrogen complex: Stepwise N2 methylation and conversion to a hafnocene hydrazonato compound

Donald J. Knobloch, David Benito-Garagorri, Wesley H. Bernskoetter, Ivan Keresztes, Emil Lobkovsky, Hannah Toomey, Paul J. Chirik

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Abstract

Treatment of the hafnocene complex bearing a strongly activated, side-on bound dinitrogen ligand, [(η5-C5Me4H) 2Hf]222, η2-N2), with two equivalents of methyl triflate yielded a mixture of products, one of which was identified as the triflato hafnocene methyl diazenide compound, (η5-C5Me 4H)2Hf(OTf)(N2(CH3)), arising from methylation of one of the nitrogen atoms. This reactivity contrasts with that of the zirconocene congener, [(η5-C5Me 4H)2Zr]222, η2-N2), where methyl triflate addition yields a variety of products that lack new nitrogen-carbon bonds. The methylated hafnocene product, (η5-C5Me4H) 2Hf(OTf)(N2(CH3)) provides a platform for additional transformations for the functionalized dinitrogen core. Treatment with additional methyl triflate results in a second nitrogen-carbon bond formation to yield a rare example of a triflato hafnocene hydrazonato complex. Loss of methane and formation of the hafnocene bis(triflate) accompany the transformation. Isotopic labeling studies and other experiments are consistent with a pathway involving initial methylation of the unsubstituted nitrogen in the methyl diazenido ligand followed by deprotonation by a triflate anion.

Original languageEnglish (US)
Pages (from-to)14903-14912
Number of pages10
JournalJournal of the American Chemical Society
Volume131
Issue number41
DOIs
StatePublished - Oct 21 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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