Stabilizing structure of tertiary amine-protected rhodium colloid dispersions in chloroform

Tertiary amine-protected rhodium colloids have been prepared in chloroform by phase transfer of a rhodium(III) salt from an aqueous to the organic phase followed by reduction with hydrogen. The rhodium colloid dispersions, thus prepared, present a narrow size distribution and are stable. The structure of the protecting amine molecules on the surface of the colloids was investigated by NMR spectroscopy, transmission electron microscopy (TEM), and hydrodynamic radius measurements according to the Taylor dispersion method. Carbon-13 NMR spectroscopy can provide some information on the conformation of the amine molecules on the surface. The size of the entire colloid including the amine layer surrounding the metal surface, obtained by the Taylor dispersion method, is considered to be fairly consistent with the size of the naked metal particles obtained by TEM and the size of the adsorbed layer, and thus supports the conformational information.