Highly active and thermo-stable iminopyridyl vanadium oxychloride catalyzed isoprene polymerization

Stereoregular polymerizations are of high importance, which disclosing the relationships between microstructures and physical properties of polymers. In this contribution, a series of iminopyridyl vanadium oxychloride complexes V1 – V8 (R = H, R¹ = CH₂Ph for V1 ; R = H, R¹ = CHPh₂ for V2 ; R = H, R¹ = octamyl for V3 ; R = H, R¹ = Ph for V4 ; R = H, R¹ = 4-OMe-C₆H₄ for V5 ; R = H, R¹ = 4-CF₃ C₆H₄ for V6 ; R = H, R¹ = 2,4,6-Ph₃ C₆H₂ for V7 and R = Me, R¹ = Ph for V8 ) have been prepared, and were investigated for their catalytic capacity of isoprene polymerization. A single crystal structure of V7′ was reported, which was reduced from V(v) to V(iv) in the oxidation state of vanadium central atom. The catalytic activity was up to 408 kg (mol V)⁻¹ hr⁻¹, when V4 was used. The catalyst V6 was found to be highly thermo-stable with excellent activity even at 100°C. Most importantly, resultant polymers mainly possessed cis-1,4 units (up to 75%) with 25% side-chain 3,4 functional group, which is particularly important component to enhance the application of these synthetic rubbers.