The surface organometallic fragment [Rh-I(P(CH3)(3))(2)(CO)], 1, was prepared by the reaction of trans-[CH3Rh(P(CH3)(3))(2)(CO)] with partially dehydroxylated silica. 1 is attached to the silica surface by a covalent bond to oxygen. The reactions of 1 with organic and inorganic substrates were followed by transmission infrared and solid-state NMR spectroscopies. Ligand exchange reactions were observed when 1 was treated with (CO)-C-13 and P(CH(CH3)(2))(3). In the presence of excess PR3 (R is methyl or isopropyl), cationic [Rh(PR3)(3)CO](+) was formed. In the presence of HCl/DCl, Cl-2, CCl3Br, CH3I, and CH2=CHCH2Cl, 1 underwent oxidative addition to give Rh(III) surface species. characterized by a shift of the v(CO) modes ca. 100 cm(-1) to higher frequency and displacement of the P-31 chemical shifts to lower field. In the case of HCl/DCl, v(Rh-H/D) modes were also observed. Oxidative addition of CH3I to 1 occurs without CO insertion. but the formation of acyl complexes was induced by addition of excess P(CH3)(3) or CO. The reaction of 1 with CH2=CHCH2Cl exhibits biphasic kinetic behavior, implying consecutive elementary reactions of oxidative addition followed by spontaneous CO insertion into the metal-carbon bond. The demonstration of these reactions on an oxide surface supports the idea that, under carefully controlled conditions, surface reactivity can be interpreted by using concepts from organometallic chemistry.