Hafnium alkyl complexes of the anionic PNP pincer ligand and possible alkylidene formation

Christina M. Brammell, Emily J. Pelton, Chun Hsing Chen, Andrey A. Yakovenko, Wei Weng, Bruce M. Foxman, Oleg V. Ozerov

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The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP = [(4-Me-2-iPr 2P-C6H3)2N]). (PNP)HfCl3 (3) was prepared via reaction of (PNP)Li (2) with HfCl4(OEt 2). Reactions of (PNP)HfCl3 with alkyl Grignards led to triple alkylation to produce (PNP)HfMe3 (4) with a small methyl or only double alkylation to give (PNP)Hf(CH2SiMe3) 2Cl (5) with a larger alkyl. Structures of 3, 4, and 5 in the solid state were established by X-ray diffraction studies. Structures of the alkyl complexes 4 and 5 display remarkably irregular coordination environments about Hf, while in 3 it is approximately octahedral. Compound 4 was found to be thermally stable at 75 °C. On the other hand, thermolysis of 5 at similar conditions led to a mixture of products, the major one of which is believed to be a Hf alkylidene on the basis of in situ NMR spectroscopic observations (e.g., δ 248.2 ppm in the 13C{1H} NMR spectrum).

Original languageEnglish (US)
Pages (from-to)4132-4137
Number of pages6
JournalJournal of Organometallic Chemistry
Issue number25
StatePublished - Dec 15 2011


  • Alkylidene
  • Hafnium
  • Metal alkyl
  • Pincer
  • X-ray crystallography

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