Abstract
Strategies for synthesis of more effective soluble supported ligands for phosphine-ligated Pd(0) cross coupling catalysts have been explored. Reversible addition-fragmentation chain transfer (RAFT) polymerization has been used to prepare alkane-soluble poly(4-alkylstyrene)-bound phosphine ligands. 4-tert-Butylstyrene and 4-dodecylstyrene were copolymerized with ca. 7 mol% of 4-chloromethylstyrene or a 4-diphenylphosphinestyrene monomer using RAFT chemistry to afford poly(tert-butylstyrene-co-4-dodecylstyrene) copolymers. Polymers with chloromethyl groups were allowed to react with the phenolic group of a hindered dicyclohexylbiarylphosphine ligand. This hindered polymer-bound phosphine formed reactive Pd complexes useful in haloarene amine couplings. All aryl halide amination reactions had Pd leaching that was typically <0.1% of the charged Pd with one example having only 0.02% Pd leaching. These Pd complexes of poly(4-alkylstyrene)-bound phosphines were also compared to similar hindered phosphine complexes formed with a polyisobutylene (PIB), whose terminus was also converted into a dicyclohexylbiarylphosphine ligand. Palladium catalysts ligated by these hindered biarylphosphines on poly(4-alkylstyrene) and PIB-bound both were recyclable in the absence of oxygen, had similar activity, and very low Pd leaching.
Original language | English |
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Pages (from-to) | 2378-2383 |
Number of pages | 6 |
Journal | Catalysis Science and Technology |
Volume | 5 |
Issue number | 4 |
DOIs | |
Publication status | Published - 1 Apr 2015 |
Externally published | Yes |