Fast-Initiating Catalysts
The initiation rate of the Grubbs' catalyst can be altered by replacing the phosphine ligand with more labile pyridine ligands. By using 3-bromopyridine the initiation rate is increased more than a million fold:
The principle application of the fast-initiating catalysts is as initiators for ring opening metathesis polymerisation (ROMP). Because of their usefulness in ROMP these catalysts are sometimes referred to as the 3rd generation Grubbs' catalysts. The high ratio of the rate of initiation to the rate of propagation makes these catalysts useful in living polymerization. Living polymerization can be used in the synthesis of block copolymers with interesting side chain functionality, taking full advantage of the high functional group tolerance of the Grubbs' catalyst.
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