HzRuOs3(C0)13], [ H 4 R~O~3 ( C 0 ) 1 2 ] , [ Et4N] [HRUOS~(CO)~,], and [Et4N] [H3RuOs,(CO) were synthesized and characterized spectroscopically, and their reactivities with the basic -OH groups on the surface of y-Al,O, were investigated, the surface species being characterized by infrared and UV-vis spectroscopy and extraction of anions. Surface-bound anions were formed by adsorption of the salts. Alternatively, the surface-bound ion pair [HRuOs,(CO),,]-(AI) was formed from [H2R~O~3(C0)13] by deprotonation on the surface; the anion is bonded to the surface through a bridging carbonyl group interacting with a surface Lewis acid site (AI3+ ion). This surface anion is readily converted at 50-70 "C into [H3RuOs3(CO),,]-(A1), evidently by reacting with surface water. The latter anion is also formed by deprotonation of [H4RuOs3(CO),z] on the surface.[H,RuOs3(CO),,]-(Al] is the precursor of a catalyst for isomerization of but-1-ene to give cis-and trans-but-2-ene at 53-77 "C. The catalytic activity and the Langmuir-Hinshelwood kinetics parameters were the same, whether the catalyst was prepared by adsorption of [Et4] [H,RUOS~(CO)~,] or from [H2RuOs3(CO)13], converted into [HRuOs,(CO),,]-{Al) and then into [H3RuOs3(C0),,]-{A1).The catalyst was stable for >2000 turnovers. Infrared spectra showed that [H3RuOs3(CO),,]-(A1) was the predominant surface organometallic species on the working catalyst. When the catalyst was used instead for ethylene hydrogenation, the activity changed as the cluster was degraded; metal particles were formed, and these and/or mononuclear metal complexes are the likely catalytic species.The new field of surface organometallic is concerned with the synthesis, structure, reactivity, and catalytic activity of surface-bound analogues of molecular organometallic structures. The work is motivated3 by opportunities to use organometallic compounds as probes of the structure and reactivity of surface^,^ by opportunities offered by molecular organometallic precursors for formation of new surface structure^,'^^^^^^ and by prospects that these surface structures will have new catalytic p r o p e r t i e~.~%~,~-I~The "molecular" surface-bound organometallics are looked upon as models of the supported metal catalysts used in technology, such as the alumina-supported Pt-Re used in reforming of petroleum naphtha* and the oxide-supported Pt-Rh used in abatement of automobile e x h a~s t .~ These technological catalysts have highly complicated structures, incorporating aggregates (crystallites) of metal of various sizes and shapes dispersed on high-area porous metal oxide supports.Many of these supported metal catalysts used in technology are bimetallics;1° combinations of metals are often more effective catalysts than single metals. Consequently, there is interest in molecular bimetallic clusters as catalysts and catalyst precursors, in solution" and on supports.'* A number of molecular monometallic clusters have been anchored to the surfaces of metal oxide supports,I3 and a few of these have been investigated ...