REACTIONS OF METAL-IONS AT FLUORINATED SURFACES - FORMATION OF MF(N)(-5)() (M=TI, CR, FE, MO, AND W, N=1)

Low-energy (<100 eV) ion/surface reactions of metal ions, Ti-.+, Cr-., Fe-.+, Mo-.+, and W-.+, at a fluorinated self-assembled monolayer su rface give fluorine-containing scattered ions, MF(n)(+), n < 5. The me tal fluorides are the most abundant products in the scattered ion spec tra. The single fluorine abstractions are all endothermic and driven b y the projectile translational energy. Multiple fluorine abstraction o ccurs with high efficiency for Mo-.+ and W-.+ projectiles, where the t hermochemistry is most favorable. Polyatomic projectile ions derived b y partial fragmentation of the Cr, Mo, and W hexacarbonyls also yield metal fluoride scattered ions, in addition to more complex species for med by fluorine abstraction by ions which retain one or more carbon at oms or carbonyl groups. Fe- and Ti-containing projectile ions, bearing one or two cyclopentadienyl (Cp) groups, also exhibit fluorine abstra ction products, with and without retention of a Cp group. TiCln+ (n = 1-4) projectiles exhibit fluorine abstraction, as well. Similar fluori ne abstraction products are generated upon collisions at a liquid perf luorinated polyether surface. Gas-phase ion/molecule reactions and the rmochemical considerations suggest that multiple fluorine abstractions can occur by a direct reaction mechanism within a single scattering e vent and that multiple fluorine atoms are probably derived from a sing le fluorocarbon chain. Angle-resolved scattering data support a single -collision, multiple-atom abstraction mechanism. The scattered ions le ave the surface with very low translational energy and collision energ y variations suggest that in these ion/surface reactions, projectile d issociation is concerted with or occurs prior to fluorine abstraction. There is no evidence that electron transfer to the surface is involve d, as it is in alkyl group abstraction reactions by ions at hydrocarbo n surfaces.