SOMC-designed silica supported tungsten Oxo imidazolin-2-iminato methyl precatalyst for olefin metathesis reactions

Abstract

Synthesis, structure, and olefin metathesis activity of a surface complex [(Si-O-)W(=O)(CH3)2- ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)- imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten- (VI) oxytetrachloride generated the tungsten oxo imidazolin-2- iminato chloride complex [ImDippNW(O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(Si-O-)W(=O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(Si-O-)W(=O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.