'Controlled Pd(0)/t-Bu3P-Catalyzed Suzuki Cross-Coupling Polymerization of AB-Type Monomers with ArPd(t-Bu3P)X or Pd-2(dba)(3)/t-Bu3P/ArX as the Initiator

摘要

Controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerizations of AB-type monomers via the chain-growth mechanism with a series of ArPd(t-Bu3P)X (X = I, Br, Cl) complexes as initiators were described. Both isolated PhPd(t-Bu3P)X (X = I, Br) complexes and ArPd(t-Bu3P)X (X = I, Br, Cl) complexes in situ generated from Pd-2(dba)(3)/t-Bu3P/ArX (X = I, Br, Cl) were employed as initiators for the controlled Pd(0)/t-Bu3P-catalyzed Suzuki cross-coupling polymerization. The in situ generated ArPd(t-Bu3P)X complexes were found to be better initiators in general. Among them, the combinations of p-BrC6H4I, p-HOCH2C6H4Br and p-PhCOC6H4Br with Pd-2(dba)(3)/t-Bu3P were identified as highly robust initiator systems, resulted in polymers with narrow PDIs (1.13-1.20). In addition, the Pd-2(dba)(3)/t-Bu3P/p-HOCH2C6H4Br and Pd-2(dba)(3)/t-Bu3P/p-PhCOC6H4Br initiator systems also offered heterobifunctional chain ends with high fidelity. Our study showed that an additional amount of t-Bu3P in the initiator system helped to achieve the narrow PDIs, likely by stabilizing Pd(0) species in the initiator system via coordination to form more stable Pd(t-Bu3P)(n) (n >= 2) complexes. Our study opens a new avenue toward well-defined conjugated polymers.