Rapid phosphine exchange on 1.5-nm gold nanoparticles.

Triphenylphosphine-cappped, 1.5-nm gold nanoparticles "Au(101)(PPh(3))(21)Cl(5)" prepared following Hutchison's procedure (Weare, W. W.; Reed, S. M.; Warner, M. G.; Hutchison, J. E. J. Am. Chem. Soc. 2000, 122, 12890) undergo rapid exchange of capping ligand phosphine with dissociated and added phosphine in dichloromethane solvent at 298 K. Remarkably, while the (1)H NMR spectrum resonances of the attached phosphine are broad, characteristic of a range of incompletely averaged environments, the (31)P NMR spectrum (observable only at 213 K and below) exhibits a single, narrow resonance indicating that all of the phosphorus atoms are magnetically equivalent.