Pdo-nanoparticles stabilized by tripodal phosphine based ligands and their catalytic activities on carbonsingle bondcarbon bond formation reactions

Tripodal ligands, 1,1,1-tris(diphenylphosphinomethyl)ethane [CH3C(CH2PPh2)3] [P3] and 1,1,1-tris(diphenylphosphinomethyl)ethane trisulphide [CH3C(CH2P(S)Ph2)3] [P3S3] have been introduced to stabilize Pdo-nanoparticles having small core diameter and narrow size distribution. The Pdo-nanoparticles were synthesized by the reduction of K2PdCl4 precursor with NaBH4 in the presence of ligand P3 or P3S3 using two phases, one pot reaction at room temperature. TEM and XRD studies indicate that P3 stabilizes smaller sized Pdo-nanoparticles (<3 nm) compared to that stabilized by P3S3 (<5 nm), which are attributable to the stronger interaction of Pdo (Soft) with P (Soft) than Pdo (Soft) with S (less Softer than P). The Pdo-nanoparticles exhibit face centered cubic (fcc) lattice geometry and high thermal stability (∼150 °C). The synthesized Pdo-nanoparticles serve as an efficient catalyst for the carbonsingle bondcarbon bond formation reactions, e.g. in Suzuki coupling reaction, aryl halides and arylboronic acids result cross-coupling products with about 94% isolated yield and 100% selectivity; in Heck coupling reaction, the vinylation of aryl halides with olefins result coupling products with 97% yield and >99% trans selectivity while in the alkynylation of aryl halides with terminal alkynes, i.e. Sonogashira coupling reaction, the cross-coupling products of about 94% isolated yield with 100% selectivity were observed. The synthesized nanocatalysts could be reused without significant loss of their catalytic activity.