Palladium Nanoparticles Entrapped In a Hydrogen Bonded Crystalline Organic Salt Matrix as a Selective Heterogeneous Reduction Catalyst

Abstract A new class of palladium nanoparticles encapsulated in an organic crystalline salt matrix Pd@F2 ( A‐2 ) was developed. Matrix A‐2 was readily prepared by mixing an aqueous solution of the tetrasodium salt of tetraphenylmethane‐tetrasulfonate and the PdCl 4 salt of protonated tetrakis(4‐aminophenyl)under hydrogen in water. Matrix A‐2 contained 17–20 % of palladium and was not pyrophoric. The average size of the palladium metal particles was 7 nm. Matrix A‐2 could be used as an efficient heterogeneous catalyst for the reduction of acetylene derivatives and had activity similar to that of Pd/C. The catalyst could be recovered and reused several times with just one four‐hundredth of the palladium leaching after the first cycle. The reduction of diphenylacetylene could be selectively stopped at the cis‐stilbene stage after one equivalent of hydrogen was absorbed. The same selective conversion could also be accomplished with terminal acetylenes. Matrix A‐2 reduced aldehyde and epoxide groups very slowly which allowed the selective reduction of the acetylenes in the presence of aldehydes. This behavior contrasts with that of Pd/C which reduces both aldehyde and acetylene groups simultaneously. A model, suggesting the selective imbedding of the aldehyde groups in the organic F2 matrix of A‐2 , isolating them from the palladium active sites, explains the observed phenomena.