Robust Chromium Precursors for Catalysis: Isolation and Structure of a Single Component Ethylene Tetramerization Precatalyst.
We have introduced a new class of stable organometallic Cr reagents (compounds 1 4) that are readily prepared, yet reactive enough to serve as precursors. They were used for ethylene tetramerization catalysis following stoichiometric activation by in situ protonation. This study highlights the importance of balancing stability with reactivity in generating an organometallic precursor that is useful in catalysis. Moreover, precursor 4 allowed for the isolation and crystallographic characterization of a room temperature stable cationic species, (PNP)CrR2+ (R o C6H4(CH2)2OMe, PNP iPrN(PPh2)2) This complex (5) may be used as a single component precatalyst, without any alkylaluminum reagents. This result provides an unprecedented level of insight into the kind of structures that must be produced from more complicated activation processes.
Journal of the American Chemical Society