Reaction of Ru 3 (CO) 1 2 with high area (≥45 m 2 g - 1 ) oxides of the rare earths, La, Ce, Pr, Tb, Ho and Yb has been studied by IR and X-ray photoelectron spectroscopy. Evidence is presented for formation of surface species [(OC) 2 Ru(OM) 2 ] n at ≤2% (wt./wt.) Ru loading for all oxides and for a surface cluster, possibly [Ru 3 (μ-H) (CO) 1 0 (μ-OM)], at 5% (wt./wt.) metal loadings for Ce and Ho oxides.