Synthesis and characterization of novel tungsten complexes and their activity in the ROMP of cyclic olefins

New tungsten complexes based on the tridentate ligand [O,N,O]-2-[(4-hydroxy-3-pentene-2-ylidene)amino]phenol (hpap) were synthesized by the direct ligation of the ligand to WOCl4, leading to the displacement of two chloride units from the metal center and the formation of cis and trans isomers of the corresponding dichloride complex. The molecular structure of cis-[WOCl2-(hpap)] was verified by X-ray crystallography. The synthesized [WOCl2-(hpap)], a mixture of both cis and trans isomers, has been demonstrated to form a highly active catalyst in the Ring Opening Metathesis Polymerization (ROMP) of cyclic olefins such as TCD and MCMT, in combination with trialkyl aluminum as a promoter. However, the effectiveness in the metathesis of polar substituted monomers was found to be slightly lower, which may be due to the interaction of monomer polar groups with the catalyst components. The chemical structure of the resulting ROMP’d poly-TCD was characterized using one and two-dimensional 1H NMR and 13C NMR spectroscopy.

New cis and trans [WOCl2-(hpap)] complexes, where (hpap) is [O,N,O]-2-[(4-hydroxy-3-pentene-2-ylidene)amino]phenol were synthesized and their catalytic capacity towards the ROMP of TCD and MCMT using trialkyl aluminum as a promoter are proved to be highly active.Figure optionsDownload as PowerPoint slideHighlights
► WOCl2-[O,N,O]-2-{(4-hydroxy-3-pentene-2-ylidene)amino}phenol] as a catalyst.
► Activated with Et3Al, [WOCl2-(hpap)] proved efficient for the ROMP of cyclic olefins.
► Polymerization outcomes are effected by the TCD/[W] ratio and the amount of co-catalyst.