Active Carbon Functionalized with Chelating Phosphine Groups for the Grafting of Model Ru and Pd Coordination Compounds

Abstract

An active carbon support has been functionalized in order to introduce at its surface chelating phosphine groups. This has been done in several steps, which have each been studied in detail and optimized in turn. The first step consisted of increasing the number of oxygenated surface groups by oxidative treatment with HNO3. The second step involved the coupling of an amine with the surface carboxylic groups by formation of an amide bond. Various coupling agents were studied, of which SOCl2 was found to be the most efficient. Fluorinated and brominated amines were used as model amines (easier surface quantification by XPS thanks to the presence of heteroatoms such as F or Br), before reacting ethylenediamine. The pending arm of the diamine could then be further transformed into the desired bidentate phosphine in the last step. The success of the procedure was confirmed, and proof for actual surface chemical reactions was obtained. Two coordination compounds, Pd(dba)(2) and Ru-3(CO)(12), were then incorporated on the starting carbon support and on the functionalized one. It was found that the presence of chelating phosphine groups at the surface of the functionalized support allowed to increase the yield of incorporation and the metallic dispersion at the surface, probably via a ligand exchange mechanism. Nanometer-sized Pd and Ru particles were evidenced by TEM.