Synthesis, Characterization, and Ligand Rearrangement of Tungsten Cyclopropyl Complexes

Abstract

In an effort to study the β-H abstraction/1,3-addition mechanism for CH bond activation, the syntheses of tungsten organometallic complexes featuring a cyclopropyl ligand were undertaken. Attempts to prepare the chloro cyclopropyl complex Cp*W(NO)Cl(c-C3H5) instead afforded the previously reported allyl complex Cp*W(NO)Cl(η3-CH2CHCH2), due to a ring-opening rearrangement of the cyclopropyl ligand. The alkyl cyclopropyl complex Cp*W(NO)(CH2SiMe3)(c-C3H5) (1TMS) was prepared and characterized in solution via NMR spectroscopy but also undergoes a ligand rearrangement process to afford the allyl complex Cp*W(NO)(CH2SiMe3)(η3-CH2CHCH2) (2TMS), which was characterized by NMR spectroscopy and an X-ray diffraction study. Attempts to inhibit the ligand rearrangement or isolate 1TMS in the solid state have been unsuccessful. In order to investigate the mechanism of the conversion of 1TMS to 2TMS, a kinetic study was undertaken, and some preliminary results are discussed.