Intra-Ligand H···F Interactions: Non-negligible Forces for Enhancing Thermostability of Cobalt Complexes in 1,3-Butadiene Polymerization

Addressing the traditional poor thermostability issues of late-transition metal is highly important for both polyolefin and polydienes industries. In this contribution, a series of α-imino-ketone and α-diimine cobalt complexes bearing intra-ligand H···F noncovalent interactions were synthesized and thoroughly characterized. From single-crystal analysis, it was found that such a H···F interaction could successfully suppress the N-aryl rotations and result in highly thermal robust active species. In the presence of ethylaluminum sesquichloride, the complexes revealed high catalytic efficiencies even at 100 °C, which is superior to fluoro-free counterparts, confirming solidly the positive influence of intra-ligand H···F interactions. Moreover, this research also disclosed that the thermal robust active species could be successfully retained in the presence of external donor PPh3. After being coordinated by the Lewis basic PPh3, the polymer yields were also appreciable, and simultaneously, the original cis-1,4- selectivity could be shifted to a highly 1,2- manner.