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.