1-Heptyne semihydrogenation catalized by palladium or rhodium complexes: Influence of: metal atom, ligands and the homo/heterogeneous condition

[RhCl(TDA)3], [RhCl(HA)3], [PdCl2(TDA)2] and [PdCl2(HA)2] (TDA = tridecylamine, HA = hexylamine) were synthesized and tested as catalysts in homogeneous and heterogeneous condition for the 1-heptyne semihydrogenation, using γ-alumina as support. The Lindlar catalyst was used as a reference. XPS, FTIR and Atomic Absorption results showed that the active catalytic species in each case is the complex itself. All of the catalytic systems exhibited a better performance than the Lindlar catalyst, with the exception of [PdCl2(HA)2]. The analysis of activity and selectivity values allowed to say that the best system is [RhCl(TDA)3]/Al2O3, an heterogeneous catalyst with an electron-rich transition metal and an electron-donating ligand (TDA) containing a long-chain hydrocarbon substituent. The complex system catalytic behaviour could be explained by means of electronic and geometric effects.

[RhCl(NH2(CH2)12CH3)3], [RhCl(NH2(CH2)5CH3)3], [PdCl2(NH2(CH2)12CH3)2] and [PdCl2(NH2(CH2)5CH3)2] were obtained and tested as catalysts in different conditions for the 1-heptyne semi-hydrogenation. All of the catalytic systems exhibited a better performance than the Lindlar catalyst, except [PdCl2(NH2(CH2)5CH3)2]. The best catalytic system was [RhCl(NH2(CH2)12CH3)3]/γAl2O3, containing an electron-rich metal and an electron-donating ligand (NH2(CH2)12CH3). This behaviour could be explained by means of electronic and geometric effects. The figure shows the conversion to 1-heptene (%) vs total 1-heptyne conversion (%) for the Rh complexes in homogeneous and heterogeneous conditions and Lindlar catalyst.Figure optionsDownload as PowerPoint slide