STEPWISE THERMOLYSIS OF TRIS(ALLYL)RHODIUM TO RHODIUM METAL - ELUCIDATION OF THERMAL-PROCESSES ON BULK TITANIA THROUGH ULTRAHIGH-VACUUM STUDIES ON TIO2(001)

Deposition of tris(allyl)rhodium onto hydroxylated bulk TiO2 was carried out at room temperature. Thermolysis of the supported organometallic occurred in stages and was analyzed by stoichiometric means and by IR spectroscopy: between 60 and 100-degrees-C, TiO2-Rh(allyl)H was obtained; between 120 and 150-degrees-C, TiO2-RhH2 was produced; above 400-degrees-C under H-2, Rh metal was formed. Deposition of tris(allyl)rhodium onto hydroxylated single crystal TiO2(001) was also carried out at room temperature under ultrahigh vacuum. With long exposure (2000 langmuirs) ca. 5% Rh atomic composition of the surface region was determined by Auger electron spectroscopy. Thermolysis of the single crystal oxide supported organometallic was followed by ultraviolet photoelectron spectroscopy (for O 2p) and X-ray photoelectron spectroscopy (XPS) (for Rh 3d5/2). Correlations were drawn with results of reactions performed on "bulk" TiO2. Results suggest covalency between surface Rh complexes and the support oxygens. Aggregation of metallic Rh on TiO2 was noted (by XPS analysis) after long reaction times.