Catalyst-Transfer Suzuki-Miyaura Condensation Polymerization of Stilbene Monomer: Different Polymerization Behavior Depending on Halide and Aryl Group of ArPd(tBu3P)X Initiator

We report Suzuki-Miyaura coupling polymerization of tetraalkoxy-substituted 4-bromostilbene-4 '-boronic acid 1 with several t-Bu3P-ligated Pd initiators; this is the first example of catalyst-transfer condensation polymerization (CTCP) of a monomer containing a carbon-carbon double bond. When o-tolylPd((Bu3P)-Bu-t)Br was used as the initiator, the o-tolyl group was not introduced at the polymer end, but polymer with boronic acid at one end and bromine at the other was obtained. However, when we employed stilbenePd((Bu3P)-Bu-t)I generated in situ from iodostilbene and Pd((Bu3P)-Bu-t)G2 precatalyst, or isolated ArPd((Bu3P)-Bu-t)X (Ar, X = Ph, I; o-tolyl, I; and Ph, Br), the aryl group was introduced at the polymer end, indicating that CTCP of 1 proceeded. Therefore, the iodide and aryl group of the Pd initiator complex is crucial for CTCP of 1. However, the molecular weight distribution of the obtained polymer was broad, possibly because coordination of the carbon-carbon double bond of 1 to ArPd((Bu3P)-Bu-t)I resulted in slow initiation. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 297-304