STUDIES OF MET-CAR ADDUCTS - TI8C12-BONDING MOLECULES, AND POLAR-MOLECULES)((M)(N) (M=HALOGENS, PI)

A new method of forming Met-Car-ligand complexes, Ti8C12+(M)(n) (M = h alogens, pi-bonding molecules, and polar molecules, n = 1-8) is report ed which involves the direct interaction of titanium with mixtures of methane and selected reactant gases. The results show that the formati on of Ti8C12 in the plasma is kinetically and thermodynamically favore d over other reaction processes. Through an examination of Met-Car-lig and complexes, various reaction mechanisms of Ti8C12+ are identified a nd characterized, namely oxidation, complexation, and iondipole intera ction. Oxidation of Ti8C12+ occurs when Met-Cars react with halogen-co ntaining molecules through valence electron donation from Ti8C12- to t he halogen atoms. When Ti8C12+ interacts with pi-bonding molecules, th e findings are consistent with the formation of ''surface complexes'' comprised of the ligand binding across two of the metal atoms in the p entagonal ring of Ti8C12+ through d-pi interaction. In these cases, th e cluster size distributions in the mass spectra of the reaction produ cts exhibit truncation at Ti8C12+(M)(4). By contrast, ion-dipole inter actions lead to the formation of Ti8C12+(M)(1-8) (M denoting polar mol ecules), which is consistent with previous findings showing that polar molecules bond to each metal site. The product distribution of Ti8C12 + with butanol at various pressures provides new evidence which serves to resolve controversies in the literature regarding observed truncat ions and their implications concerning the geometric structure of Ti8C 12+; the findings are supportive of the originally proposed T-h symmet ry. Furthermore, the further reaction of Ti8C12+; (I) with methanol, w hich gives the product distribution truncation at Ti8C12+(I)(CH3OH)(7) ), indicates that the titration method is a useful tool to probe the c luster structures in these systems.