Direct inclusion of triphenylphosphine derivatives into the zeolite Y supercage

Abstract

Thermal treatment of a mixture of triphenylphosphine (1) and zeolite Y at 423 K resulted in inclusion of the former into the zeolite supercage (SC), with up to 1.5 molecules per SC. Similar behavior was observed for cyclohexyldiphenylphosphine and diphosphines. The included molecules were strongly bound by zeolite Y, with desorption observed at higher temperature compared with those of unloaded phosphines. In contrast, inclusion of diphenylmethylphosphine and tri-p-tolylphosphine hardly occurred. The reversible inclusion and desorption of 1 were induced by thermal treatment at 423 and 873 K, respectively. The amount of included 1 increased with the decreasing Al content of zeolite Y, suggesting van der Waals forces as the driving force of inclusion. Calculations using molecular dynamics and density functional theory revealed that each of the three phenyl groups of 1 was inserted into the 12-membered rings of zeolite Y, thus forming inclusion compounds. PdCl2 introduced into the 1-included zeolite Y exhibited high turnover frequency (2.5 × 104 h−1) in the allylic alkylation, suggesting that the PdCl2(PPh3)2 complex included in the SC could be the catalytically active species.