Self-Diffusion Coefficients of Transition-Metal Complex Ions, Ion Pairs, and Higher Aggregates by Pulsed Field Gradient Spin−Echo NMR Measurements

The molecular self-diffusion coefficients of the complexes trans-[Ru(PMe<INF>3</INF>)<INF>2</INF>(CO)(COMe)(pz<INF>2</INF>-CH<INF>2</INF>)]BPh<INF>4</INF> and trans-[Ru(PMe<INF>3</INF>)<INF>2</INF>(CO)(COMe)(pz<INF>2</INF>-BH<INF>2</INF>)] have been measured by pulsed field gradient spin−echo NMR measurements in nitromethane, chloroform, and methylene chloride as a function of concentration. By using the neutral complex as reference with the assumption that it does not undergo associative processes, clear indications of the presence of ions (in nitromethane), ion pairs (in chloroform at low concentration), and ion quadruples (in chloroform at high concentration) have been obtained.