As it can be observed in the kinetic profile of ethylene polymerization -Figure 1- using the dinuclear catalysts in presence of MMAO as cocatlyst, effect of the bridge structure and backbone of the ligands are very striking. Based on the results, higher electronic effects and electron density on the metal center which can stabilize the catalyst leads to higher activity and stability of the complexes. However, this effect along with some possible interactions such as deactivation and less shielding of axial sites around the active center revealed an opposite impact on the catalyst performance. This behavior was observed for dinuclear polymethylene bridged catalysts. However, by increasing the methylene groups on the bridge activity increased due to less negative effect and higher stability. The nature of the bridge also exhibited high impact on the kinetics of the polymerization. The catalyst bearing aromatic rings on the bridge between the centers showed higher productivity in comparison to catalysts with the linear aliphatic linker. Moreover, presence of the two phenyl rings caused greater activity than one. The result is due to the higher electronic effects of electron rich rings between the centers. In addition, it is proved that the presence of bulky groups such as acenaphthene in the backbone structure in term of steric, electronic and structural impact on the active site which can block the equatorial situations of the metal center and open the axial situations can lead to increasing of the catalyst activity.

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