Much progress has been made in catalyst-transfer polymerization (CTP) to control the synthesis of π-conjugated polymers, which are attractive targets for organic electronics. Attempts to improve the methodology of CTP have focused on the mechanistic influences of reactive ligands, ancillary ligands, and the transition metal on the rate of initiation and propagation. One avenue that has not been relatively explored is the utilization of multimetallic cooperative catalysts. In this work, catalysts designed from a 1,4- and 1,3-N,N,N’,N’-tetra(diphenylphosphanylmethyl)benzene diamine bridging ligand complexed to two Ni metal centers were employed in a Kumada CTP to synthesize poly(3-hexylthiophene) (P3HT). To explore the behavior of bimetallic complexes in CTP, a comparative study that included the monometallic analogue and Ni(dppp)Cl2 as the control was completed using solution 1H-NMR kinetics, MALDI-TOF, and GPC to characterize monomer conversion, degree of polymerization, end-group functionalization and molecular weight (MW) distribution. The obtained data revealed that all catalysts synthesized P3HT via chain-growth, and displayed similar kinetics with monomers that contained one or three thiophene rings in length. The similar kinetics indicate the Ni metal centers are acting independent of each other with no apparent cooperative effects. Endgroup analysis and observed MW distribution revealed worse CTP performance in the bimetallic and monometallic catalysts compared to Ni(dppp)Cl2. This reduced performance can be attributed to a weaker Ni(0)-π-aryl complex, which was caused by the crowding of the coordination plane with two polymer chains growing simultaneously.

Exploring the behavior of bimetallic organonickel complexes in the controlled synthesis of π-conjugated polymers

2019 Fall National Meeting

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