1 H, 1H–{103Rh} INDOR, and 13C n.m.r. spectroscopy has been used to show that the hydrogens in [Rh13(CO24)H5 –n]n–(n= 2 or 3) migrate rapidly around the inside of the hexagonal close-packed cluster; 13C n.m.r. spectroscopy also shows that at room temperature all the edge-bridging carbonyl groups, except for the 3 carbonyl groups which bridge the rhodium atoms in the hexagonal plane, undergo exchange with the 12 terminal carbonyl groups on the outside of the cluster.