Additive Effect of Triphenylphosphine on the Living Polymerization of 1,3‐Butadiene with a Cobalt Dichloride‐Methylaluminoxane Catalytic System

Abstract

The additive effect of triphenylphosphine (Ph3P) was investigated in 1,3‐butadiene polymerization with cobalt dichloride (CoCl2) activated by methylaluminoxane (MAO); the catalytic system resulted in slowly‐initiated living polymerization with a high cis‐1,4 content (about 99%) at 0 °C. The polymerization behavior, such as the relationship of polymer yield and number‐average molecular weight ($\overline M _{\rm n}$) with polymerization time, was dependent on the amount of Ph3P added. In the presence of a small amount of Ph3P (Ph3P/Co = 0.025), the kinetic behavior qualitatively resembled that observed in the absence of Ph3P, which indicated that the catalytic system conducted slowly‐initiated living polymerization. An increase in the amount of Ph3P (Ph3P/Co > 0.025), however, caused chain transfer reaction. The 1H NMR analysis of the produced polymers showed that Ph3P changed the microtacticity from 99% of cis‐1,4 to 88% of 1,2‐unit, depending on the amount of Ph3P added. At the maximum amount of Ph3P (Ph3P/Co = 0.025) necessary for maintaining the livingness of the propagating species, 14% of the 1,2‐inserted unit was incorporated at the expense of the cis‐1,4‐inserted unit. The addition of Ph3P (Ph3P/Co = 0.025) during the polymerization did not affect the livingness and gave a regio‐block copolymer of 1,3‐butadiene.

Stereospecific polymerization of 1,3-butadiene catalyzed by cobalt complexes bearing N-containing diphosphine PNP ligands

“…It is interesting to notice that much higher conversion of butadiene was obtained when the imino group in ligand L3 was reduced to amino group (ligand L4), comparing complex 3 (conversion: 12.7%) with complex 4 (conversion: 46.1%) although the nitrogen atoms were not coordinated to the cobalt center (entries 4 and 5 in Table 1). Similar to the results reported in the literature [16,17], the 5/MAO system produced much more amount of 1,2-PBD (1,2-vinyl content: 76.9%) than cis-1,4-PBD (cis-1,4 content: 20.6%) because the nature of PPh 3 as a strong s-donor makes it more preferable to gain a high content of 1,2-PBD (entry 6 in Table 1). However, for the chelate complexes 1a, 1b, and 2e4/ MAO systems, the cis-1,4-PBD as the main product ranging from 75.7% to 88.8% was obtained along with a relatively higher content (9.0%e20.6%) of 1,2-PBD formed.…”

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

“…Diverse ancillary ligands, such as N^N^N, N^N^O, N^C^N, N^N, O^P architectures were designed and synthesized. The corresponding Co(II) and Fe(II) complexes were further employed in (co‐)polymerization of dienes . Very recently, Huang and other groups reported Co(II) complexes for isoprene polymerization that offer high activity, precise control over the molecular weight and high cis ‐1,4‐alt‐3,4 microstructures .…”

Synthesis and characterization of soft-hard stereoblock polybutadiene with Fe(2-EHA)3 /Al(i -Bu)3 /DEP catalyst system

“…1,2‐1,4‐1,2 Triblock and high trans −1,4‐ b ‐low cis −1,4‐ b ‐high trans −1,4 PBD with narrow molecular weight distributions (MWDs) were prepared through the sequential anionic polymerization of 1,3‐butadiene (BD) with different additives . Regioblock PBD composed of cis −1,4 and s‐1,2 blocks was synthesized with Co‐based catalyst via reversible coordination of phosphine …”