Synthesis and Catalytic Application of a Novel Recyclable Thermoregulated Phase-Transfer Phosphine Ligand

Organometallic complexes are widely used as efficient homogeneous catalysts in organic synthesis, but their recycling remains difficult. In this study, a novel LTRPT22-Pd(0) nanocatalyst with thermoregulated phase-transfer functionality was designed and synthesized, and its catalytic activity and recyclability in the Mizoroki–Heck reaction were investigated. The rationally designed phosphine ligand LTRPT22 contains a bulky electron-rich aryl moiety and flexible polyether chain segments, whose synergistic effect enables the resulting LTRPT22-Pd(0) nanocatalyst to combine the high activity of homogeneous catalysts with the facile recoverability of heterogeneous catalysts. The results showed that the LTRPT22-Pd(0) nanocatalyst exhibited excellent thermoregulated phase-transfer behavior in mixed aqueous/organic solvents, migrating to the organic phase upon heating and returning to the aqueous phase upon cooling, with a phase-transfer temperature of 47 °C. At 85 °C, the LTRPT22-Pd(0) nanocatalyst catalyzed the Mizoroki–Heck reaction of iodobenzene with butyl acrylate in a water/toluene biphasic system, affording a yield of over 92% (98% in pure toluene). The nanocatalyst could be recovered by simple phase separation and reused up to four times in this model reaction. These results demonstrate that the combination of steric and electronic modulation of the ligand with a thermoregulated phase-transfer functionalization strategy can overcome the intrinsic trade-off between high activity and easy recovery in conventional catalytic systems, thus providing a feasible approach for the development of novel efficient and recyclable palladium catalysts.