Rhodium(I) Complex with Hexylamine and Chloride Ligands, Catalytically Active in the Selective Hydrogenation of 1-Heptyne

A rhodium(I) complex containing chloro and hexylamine was obtained. This species shows catalytic activity for the 1-heptyne semihydrogenation under at mild conditions (303 K and 150 kPa) in homogeneous as well as heterogeneous systems using (gamma)-alumina as support. Fourier transform infrared (FTIR) spectra indicate that the hexylamine molecule is one of the ligands present in the complex species. On the other hand, the analysis of the results of X-ray photoelectron spectroscopy (XPS) and elemental composition suggest that the complex is tetracoordinated with an empirical formula [RhCl(NH2(CH2)5CH3)3], and that it attaches to the support and is not destroyed under reaction conditions. The absence of complex leaching from the supported catalyst was verified by XPS, atomic absorption analysis for Rh in solution, and catalyst reuse tests. When supported, the complex shows higher activity and selectivity than it does when it is unsupported, and also higher activity than the classic Lindlar catalyst used as a reference; this fact may be attributed, at least in part, to electronic and geometric effects.