摘要:
The diarylamido-based PNP pincer ligand can be used successfully for support of organometallic Hf complexes (PNP - [(4-Me-2-(Pr2P)-Pr-i-C6H3)(2)N]). (PNP)HfCl3 (3) was prepared via reaction of (PNP)Li (2) with HfCl4(OEt2). 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)(2)Cl (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 degrees 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., delta 248.2 ppm in the C-13{H-1} NMR spectrum). (C) 2011 Elsevier B.V. All rights reserved.