SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

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.