Maity, Niladri; Barman, Samir; Minenkov, Yury; Ould-Chikh, Samy; Abou-Hamad, Edy; Ma, Tao; Qureshi, Ziyauddin; Cavallo, Luigi; D’Elia, Valerio; Gates, Bruce C.; Basset, Jean-Marie(ACS Catalysis, American Chemical Society (ACS), 2018-02-15)[Article]
A well-defined silica-supported monoalkylated tungsten dioxo complex [(Si-O-)W(=O)(CH-Bu)] was prepared by treatment of highly dehydroxylated silica (SiO: silica treated at 700 °C under high vacuum) with an ionic precursor complex [NEt][W(=O)(CH-Bu)]. The identity of the resulting neutral monoalkylated tungsten dioxo surface complex was established by means of elemental microanalysis and spectroscopic studies (IR, solid-state NMR, Raman, and X-ray absorption spectroscopies). The supported tungsten complex was found to act as a precatalyst for the self-metathesis of 1-octene in a batch reactor. The mechanistic implications of this reaction are discussed with the support of DFT calculations highlighting the potential occurrence of thus-far unexplored mechanistic pathways.
Aljuhani, Maha A.; Barman, Samir; Abou-Hamad, Edy; Gurinov, Andrei; Ould-Chikh, Samy; Guan, Erjia; Jedidi, Abdesslem; Cavallo, Luigi; Gates, Bruce C.; Pelletier, Jeremie; Basset, Jean-Marie(ACS Catalysis, American Chemical Society (ACS), 2018-09-04)[Article]
ABSTRACT: Well-defined single-site silica-supported haf-niaaziridine complex [(≡Si-O-)Hf(η2-MeNCH2)(η1-NMe2)(η1-HNMe2)] was prepared using surface organometallic chemistry. Upon thermal treatment under high vacuum, the grafted spe-cies was converted into an unprecedented hafnium imido, bis-amido, complex [(≡Si-O-)Hf(=NMe)(η1-NMe2)]. The surface complexes were characterized by elemental analysis and the following spectroscopic techniques: infrared, solid-state single and multiple quantum NMR, advanced DNP-SENS, and ex-tended X-ray absorption fine structure. [(≡Si-O-)Hf(=NMe)(η1-NMe2)] catalyzed imine metathesis under mild conditions, and characterization of the reactivity showed that the imido ex-change with N-(4-phenylbenzylidene)benzylamine yielded [(≡Si-O-)Hf (η2-NMeNCH2ArCH2) (η1-NMe2)], demonstrating a kind of 2+2 mechanism involving the imine and the imido, proposed reaction mechanism is also supported by DFT calculations.
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